The 100 most-cited articles in The Journal of Physical Chemistry C, 2024

High Resolution Image Download MS PowerPoint Slide The local microenvironment has recently been found to play a major role in the electrocatalytic activity of nanomaterials. Modulating the microenvironment by adding alkali metal cations into the electrolyte can be used to either suppress hydrogen or oxygen evolution, thereby extending the electrochemical window of energy storage systems, or to tune the selectivity of electrocatalysts. MXenes are a large family of two-dimensional transition metal carbides, nitrides, and carbonitrides that have shown potential for use in electrochemical energy storage applications. Due to their negatively charged surfaces, MXenes can accommodate cations and water molecules between the layers. Nevertheless, the nature of the aqueous microenvironment in the MXene interlayer space is poorly understood. Here, we apply Fourier transform infrared spectroscopy (FTIR) to probe the hydrogen bonding of intercalated water in Ti 3 C 2 T x as a function of intercalated cation and relative humidity. Substantial changes in the FTIR spectra after cation exchange…

Mild steel (MS) is one of the most widely used materials in industry. But, this metal corrodes easily, especially in acidic solutions. Therefore, protection of this metal is critical. The use of inhibitors is one of the most practical and economical ways of achieving this. The corrosion inhibition performance of Pyronin B (PyB) for the protection of mild steel (MS) was investigated in 1 M HCl solution using the change of open circuit potential with exposure time ( E ocp- t ), potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) techniques. The surface of the MS was examined by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM) and contact angle measurements. The electrochemical stability of the PyB film formed on the MS surface was investigated by cyclic voltammetry (CV). The excess surface charge of the metal in the inhibited solution was estimated with the help of EIS studies. The experimental data were supported by theoretical approaches such as density…

High Resolution Image Download MS PowerPoint Slide In this study, dielectric constants ( D k ) and dissipation factors ( D f ) of 15 types of polyimides (PIs), including wholly aromatic, semialicyclic, partially fluorinated, and perfluorinated PIs, were measured in the transverse electric (TE 011 ) mode at a frequency of 10 GHz and analyzed based on their chemical structures and the dominant factors of dielectric polarization per unit volume ( P t ). The relationships among the dipolar orientational ( P d ) and electronic ( P e ) polarizations and dielectric properties ( D k and D f ) were quantitatively investigated. Although a systematic correlation between the structure and D f of PIs has not yet been established, we found that the D f of PIs is anisotropic and linearly proportional to P d in the in-plane direction, which can be estimated from the D k and in-plane refractive index ( n TE ) at 1310 nm. This could be related to the bidirectional relationship between the real ( D k ) and imaginary ( D f ) parts of the relative permittivity. Furthermore, the D k and D f of all PIs…

. Nevertheless, B-site doping of PeNCs has a more significant impact on the bandgap level through modification of surface defect states. In this perspective, we delve into the synthesis of PeNCs with A/B-site doping and their impacts on the structural and optoelectronic properties, as well as their impacts on the performance of subsequent PeLEDs. Furthermore, we explore the A-site and B-site doping mechanisms and the impact of device architecture on doped PeNCs to maximize the performance and stability of PeLEDs. This work presents a comprehensive overview of the studies on A-site and B-site doping in PeNCs and approaches to unlock their full potential in the next generation of LEDs.

High Resolution Image Download MS PowerPoint Slide “Smart” materials are gaining widespread attention and popularity due to their innovative ability to provide additional functionalities that go beyond the capabilities of traditional materials. Moreover, interesting phenomena surge at the transition from the microscale to the nanoscale, where significant changes in their properties occur due to the emergence of quantum effects. However, these often combine materials of different nature which might be difficult to merge. This can be solved by the use of core–shell structures, as they have the ability to combine different materials with an enhanced functionality allowing for their application-specific tailoring. Here, various synthesis techniques of core–shell nanostructures featuring a conductive shell are outlined, including physical and chemical methods, and their influence on the final electrical properties of the nanoparticles. This work also discusses the most common conductive polymers used as shell materials, exploring their impact on the nanoparticles’ performance.…

We theoretically demonstrate a high- Q and intense lattice plasmon resonance supported by the hexagonal nonclose packed thin silver nanoshells array. By introducing the diffraction coupling mechanism, the high- Q and intense lattice plasmon mode stemmed from the coupling between the TM 1 cavity plasmon mode and the diffraction mode of the first-order Wood anomaly is obtained in the thin silver nanoshells array, successfully solving the trade-off between the Q -factor and the resonance intensity of the cavity plasmon mode existed in a single silver nanoshell. In particular, a maximum Q -factor up to 610 of the lattice plasmon resonance is successfully achieved at 870 nm in the silver nanoshell array with an optimal silver thickness of 20 nm.

Among the important properties of metal-organic frameworks (MOFs) is stability, which may limit applications, for example, in separations and catalysis. Many MOFs consist of metal oxo cluster nodes connected by carboxylate linkers. Addressing MOF stability, we highlight connections between metal oxo cluster chemistry and MOF node chemistry, including results characterizing Keggin ions and biological clusters. MOF syntheses yield diverse metal oxo cluster node structures, with varying numbers of metal atoms (3-13) and the tendency to form chains. MOF stabilities reflect a balance between the number of node-linker connections and the degree of node hydrolysis. We summarize literature results showing how MOF stability (the temperature of decomposition in air) depends on the degree of hydrolysis/condensation of the node metals, which is correlated to their degree of substitution with linkers. We suggest that this correlation may help guide the discovery of stable new MOFs, and we foresee opportunities for progress in MOF chemistry emerging from progress in metal oxo cluster chemistry.

High Resolution Image Download MS PowerPoint Slide Ethylene carbonate (EC) and vinylene carbonate (VC) are the archetypical electrolyte solvent and additive in Li-ion batteries (LIBs), respectively. However, our understanding of their reaction pathways remains incomplete. Herein, the reaction pathways of EC and VC are explored by using online electrochemical mass spectrometry complemented by nuclear magnetic resonance analysis. For EC, reduction occurs through two distinct pathways <0.8 V vs Li + /Li, one yielding C 2 H 4 and the other yielding CO, depending on the electrode potential and the EC concentration. The CO-releasing pathway does not contribute to the solid electrolyte interphase formation. For VC, reduction commences at <1.9 V, but CO 2 gas evolution proceeds through a chemical step via a nucleophilic attack and VC ring opening. Additionally, VC scavenges H 2 O and reduced protons via hydrolysis and via proton abstraction from the carbon electrode to form EC. Our study uncovers further reaction pathways and underscores the unique properties of EC and VC, both individually…

While porous anodic oxides have been extensively studied, there is limited research on the specific role of fluoride ions in the anodization. This study compares the morphology of titanium anodization products before and after the addition of ammonium pentaborate to the NH 4 F electrolyte. The current–time curve in anodization is analyzed to elucidate the real role of fluoride ions. The findings indicate that the real role of fluoride ions in the anodization is to form an anionic contaminated layer and cause the generation of electronic current, triggering the oxygen bubble mold effect and promoting nanotube growth. However, when pentaborate anions are introduced in the anionic contaminated layer, they hinder the production of electronic current, leading to a significant reduction in electronic current. Consequently, the growth rate of nanotubes decreases, resulting in the formation of bulb-shaped nanotube embryos. This study provides interesting evidence supporting the role of fluoride ions by combining the ionic and electronic current theory with the oxygen bubble mold effect.…

High Resolution Image Download MS PowerPoint Slide Using the example of a proton adsorption process, we analyze and compare two prominent modeling approaches in computational electrochemistry at metallic electrodes─electronically canonical, constant-charge and electronically grand-canonical, constant-potential calculations. We first confirm that both methodologies yield consistent results for the differential free energy change in the infinite cell size limit. This validation emphasizes that, fundamentally, both methods are equally valid and precise. In practice, the grand-canonical, constant-potential approach shows superior interpretability and size convergence as it aligns closer to experimental ensembles and exhibits smaller finite-size effects. On the other hand, constant-charge calculations exhibit greater resilience against discrepancies, such as deviations in interfacial capacitance and absolute potential alignment, as their results inherently only depend on the surface charge and not on the modeled charge vs potential relation. The present analysis thus offers valuable…

X-ray photoelectron spectroscopy (XPS) is one of the most common techniques used to analyze the surface composition of catalysts and support materials used in polymer electrolyte membrane (PEM) fuel cells and electrolyzers, providing important insights for further improvement of their properties. Characterization of catalyst layers (CLs) is more challenging, which can be at least partially attributed to the instability of ionomer materials such as Nafion during measurements. This work explores the stability of Nafion during XPS measurements, illuminating and addressing Nafion degradation concerns. The extent of Nafion damage as a function of XPS instrumentation, measurement conditions, and sample properties was evaluated across multiple instruments. Results revealed that significant Nafion damage to the ion-conducting sulfonic acid species (>50% loss in sulfur signal) may occur in a relatively short time frame (tens of minutes) depending on the exact nature of the sample and XPS instrument. This motivated the development and validation of a multipoint XPS data acquisition protocol…

High Resolution Image Download MS PowerPoint Slide In semiconductor-based photocatalysis, one of the most significant directions in future research is designing materials with improved activity for the targeted photodegradation of organic contaminants. However, obtaining such photocatalysts requires an in-depth mechanistic understanding of the involved interfacial processes. In this framework, a comprehensive knowledge of photocatalysts’ ability to produce particular reactive oxygen species (ROS) and their interaction with contaminants is particularly crucial. This work aims to examine how the phase composition of SnO 2 /SnS 2 -based nanomaterials (from bare SnO 2 to SnS 2 ) affects their ability to generate various ROS and propose the corresponding photodegradation mechanism. To this end, we combined three methods: scavenger tests, electron paramagnetic resonance (EPR) spin trapping techniques, and UV–vis nitro blue tetrazolium (NBT) assay. To demonstrate the implications of different ROS involved in the photodegradation of a particular substance, indigo carmine (IC) dye was chosen…

The design and development of a multiheterostructure interface signifies a promising route to overcome the drawbacks of single-component and traditional heterostructured photocatalysts. Herein, a one-dimensional (1D)/two-dimensional (2D)/2D heterostructure, α-MnO 2 @B/O-g-C 3 N 4 /d-Ti 3 C 2, is constructed by a facile two-step synthesis method to ensure charge separation and is utilized for photocatalytic H 2 O 2 production and H 2 evolution. The formation of the individual materials and nanohybrids as well as the 1D/2D/2D interfacial interaction is ascertained by X-ray diffraction, Raman, and electron microscopy studies, respectively. 5-MX/MBOCN shows optimum photocatalytic H 2 O 2 production (2846.4 μmol h –1 g –1 ) with 10% ethanol and H 2 evolution (897.2 μmol h –1 ), which is, respectively, 2.5 and 1.6 times higher than that of the binary MBOCN counterpart. The greater cathodic current density from linear sweep voltammetry, hindered charge recombination from electrochemical impedance spectroscopy and photoluminescence measurement, and better photodurability all systematically…

Computational high-throughput studies, especially in research on high-entropy materials and catalysts, are hampered by high-dimensional composition spaces and myriad structural microstates. They present bottlenecks to the conventional use of density functional theory calculations, and consequently, the use of machine-learned potentials is becoming increasingly prevalent in atomic structure simulations. In this communication, we show the results of adjusting and fine-tuning the pretrained EquiformerV2 model from the Open Catalyst Project to infer adsorption energies of *OH and *O on the out-of-domain high-entropy alloy Ag–Ir–Pd–Pt–Ru. By applying an energy filter based on the local environment of the binding site, the zero-shot inference is markedly improved, and through few-shot fine-tuning the model yields state-of-the-art accuracy. It is also found that EquiformerV2, assuming the role of general machine learning potential, is able to inform a smaller, more focused direct inference model. This knowledge distillation setup boosts performance on complex binding sites. Collectively,…

Abstract Poly(ethylene oxide) (PEO)-based solid polymer electrolytes are pivotal in advancing high-energy-density solid-state battery technology, particularly for lithium-ion and other rechargeable batteries. PEO-based polymer electrolytes are regarded as promising due to their high conductivity and stability. However, conventional linear PEO exhibits limited ionic conductivity, attributed to the high crystallinity of the ethylene oxide (EO) chains. This crystallinity impedes ion migration, particularly at low temperatures. Various strategies have been employed to reduce the crystallinity of PEO to enhance the ionic conductivity of PEO-based electrolytes. Moreover, the electrochemical window and compatibility with both electrodes are critical. Scientists have investigated diverse approaches to enhance interfacial performance with electrodes for better electrochemical stability. This Review summarizes the latest research advancements in PEO-based solid polymer electrolytes for lithium-ion batteries, emphasizing enhancements in ionic transport properties, mechanical performance,…

The conversion of solar energy into hydrogen energy using photocatalysis technology is of great significance for the green and sustainable development of global energy. However, the lower catalytic efficiency limits the practical application of hydrogen production by the photolysis of water. In this work, a two-dimensional AlN/SPtSe-I van der Waals heterojunction is cleverly designed, and its photocatalytic water-splitting performance is investigated by first-principles calculations. Our results suggest that AlN/SPtSe-I shows narrower band gaps, suitable band edge positions, stronger light absorption, and separated photogenerated electron–hole pairs, showing excellent photocatalytic performance. Furthermore, based on the catalytic reaction mechanism of type-II and direct Z-scheme heterojunction, we calculated the Gibbs free energy of different intermediates in the entire process of photocatalytic water splitting and determined from the perspective of the reaction kinetics that AlN/SPtSe-I belongs to a typical direct Z-scheme heterojunction, indicating that it has a stronger redox…

Hydrogen has emerged as a green and sustainable alternative renewable energy source for fuel cells. Recently, MXenes have been proposed as versatile materials for hydrogen storage and various energy-related applications. Herein, monolayer and bilayer V 2 N MXenes have been studied for hydrogen storage performances through first-principles computations. The structural stability and electronic properties like bandgap and density of states of V 2 N MXene are first investigated using density functional theory calculations. Monolayered V 2 N MXene exhibits average adsorption energy between −0.80 and −0.32 eV, whereas bilayered V 2 N shows values between +0.27 and −0.35 eV for Y and Z adsorption sites. Further, Kubas interaction has been observed for both MXene structures at Y and Z sites through adsorption energy and projected density of states analyses. The calculated gravimetric storage capacity for monolayer and bilayer V 2 N is 6.86 and 5.45 wt %, respectively. All of the H 2 adsorbed on both monolayer and bilayer V 2 N MXene structures is exclusively attributed to the Kubas…

High Resolution Image Download MS PowerPoint Slide The successful application of machine learning (ML) in catalyst design has been made difficult by the challenges associated with collecting high-quality and diverse data. Due to the complex interactions between catalyst components, the design of novel catalysts has long relied on trial-and-error, a costly and labor-intensive process that results in scarce data that is heavily biased toward undesired, low-yield catalysts. Such data presents a challenge for training ML models that generalize well to novel compositions, which is necessary for the success of ML-guided catalyst discovery. Despite the growing popularity of ML applications in this field, most efforts so far have not focused on dealing with the challenges presented by such experimental data. In this work, we introduce a robust ML and explainable artificial intelligence (XAI) framework that incorporates a series of well-established ML methods designed to improve model performance and provide reliable evaluations for catalytic yield classification in the context of scarce and…

Electrocatalysis has emerged as a pivotal field for sustainable energy and environmental solutions, fueling the development of diverse electrocatalysts over the past 2 decades. However, a comprehensive understanding of the intricate dynamical processes governing electrochemical reactions remains elusive and is hampering efficient catalyst design. Surface-sensitive techniques like in situ/operando Raman spectroscopy are indispensable for characterizing these dynamic processes and guiding the development of novel catalysts. This review systematically summarizes recent advances in employing in situ/operando Raman techniques, with a particular emphasis on surface-enhanced Raman spectroscopy (SERS), for probing various electrocatalytic systems. It discusses the development, advantages, and available configurations of these Raman techniques. Moreover, the review underscores the potential of in situ SERS in unraveling the intricate mechanisms of the oxygen evolution reaction (OER) through innovative strategies and methodological advancements. Notably, leveraging SERS for novel OER…

High Resolution Image Download MS PowerPoint Slide Vibrational sum-frequency generation (SFG) has become a dominant technique in the study of molecular interfaces owing to its capabilities for molecular recognition and specificity to anisotropic structure. Nevertheless, one crucial and influential aspect of the interfacial structure, namely, its inherent three-dimensional, depth-dependent nature, cannot be obtained through conventional SFG measurements. Furthermore, not only has this depth information been so far experimentally inaccessible through SFG, the simple existence of extended anisotropic depth also complicates the analysis and interpretation of any obtained spectra. In this Perspective, we analyze the role of depth-dependent structural anisotropy in second-order vibrational spectroscopy and explore various possibilities for how the desired depth information can be experimentally attained. Using aqueous interfaces as an important and widespread example system, we highlight the prevalence of such spatially extended depth profiles, demonstrate how signals from these regions…

Fundamental understanding of the key species during the electrochemical reaction process is of vital importance to mechanistic investigation and catalyst design and heavily relies on experimental observations. The electrochemical in situ Raman technique is regarded as a powerful tool to address this challenge, as its collected signals can spectroscopically fingerprint the species related to reaction details and track their dynamic evolution. In this Perspective, we provide an overview of the recent developments about in situ Raman characterizations for electrochemical reactions. We exemplify the merits of this spectroscopic technique in monitoring the surface structure reconstruction and reaction intermediate evolution at the electrified interface of electrocatalyst hosts. We also discuss how to interpret the underlying reaction mechanism in accordance with Raman observations. In the end, we present future perspectives to cordially anticipate their more insightful contribution to sustainable research fields including electrocatalysis, spectroelectrochemistry, and beyond.

High Resolution Image Download MS PowerPoint Slide Color centers in hexagonal boron nitride (hBN) have become an intensively researched system due to their potential applications in quantum technologies. There has been a large variety of defects being fabricated, yet, for many of them, the atomic origin remains unclear. The direct imaging of the defect is technically very challenging, in particular since, in a diffraction-limited spot, there are many defects and then one has to identify the one that is optically active. Another approach is to compare the photophysical properties with theoretical simulations and identify which defect has a matching signature. It has been shown that a single property for this is insufficient and causes misassignments. Here, we publish a density functional theory-based searchable online database covering the electronic structure of hBN defects (257 triplet and 211 singlet configurations), as well as their photophysical fingerprint (excited state lifetime, quantum efficiency, transition dipole moment and orientation, polarization visibility, and many…

Kelvin probe force microscopy (KPFM) is an increasingly popular scanning probe microscopy technique used for nanoscale imaging of surface potential for various materials, such as metals, semiconductors, biological samples, and photovoltaics, to reveal their surface work function and/or local accumulation of charges. This featured review outlines the operation principles and applications of KPFM, including several typical commercially available variants. We highlight the significance of surface potential measurements, present the details of the method operation, and discuss the causes of the limitation on spatial resolution. Then, we present the pulsed force Kelvin probe force microscopy (PF-KPFM) as an innovative improvement to KPFM, which provides an enhanced spatial resolution of <10 nm under ambient conditions. PF-KPFM is promising for the characterization of heterogeneous materials with spatial variations of electrical properties. It will be especially instrumental for investigating emerging perovskite photovoltaics, heterogeneous catalysts, 2D materials, and ferroelectric…

FeOCl has attracted much attention for its good photo-Fenton properties. However, there are still some limitations to the removal efficiency of organic pollutants. Visible-light-responsive FeOCl/CdS quantum dot composites were prepared by calcination to overcome their flaws, and their catalytic activity was explored by the degradation of acid orange II (AO-II). The experimental results showed that the FeOCl/CdS composites exhibited better catalytic performance than pure components. The F 1 Cd 0.5 composite (mass ratio of FeOCl to CdS is 1:0.5) achieved 98.5% removal efficiency of AO-II, which is 14.8 times higher than that of FeOCl+CdS under similar experimental conditions; moreover, the F 1 Cd 0.5 composite still exhibits a high stability after five cycles. According to the characterization and experimental results with density functional theory calculations together, it is proposed that the type II carrier transfer-separation mechanism plays a leading role in enhancing the photodegradation performance of the photo-Fenton catalysts. This study provides a new idea to further improve…

Iron-based metal–organic frameworks (MOFs) have shown potential as catalysts for the electrocatalysis oxygen evolution reaction (OER). Despite numerous methods being employed to enhance the OER performance of MOFs, the influence of halogen-containing linkers on the electronic structure of iron-based MOF catalysts remains unexplored. In this study, a series of Fe-based MOFs (denoted as MOF-R, where R = H, Cl, or Br) with comparable structures are synthesized by changing the organic linkers coordinated with the Fe metal active center, with the aim of investigating the influence of halogen-containing linkers on the OER activity. Significantly, MOF-Br exhibited superior OER activity compared to MOF-Cl and MOF-H. Density functional theory calculations reveal that the tuning of halogen groups on organic linkers can modulate the electronic structure of the metal active sites and effectively regulate the adsorption behavior of key intermediates near the optimal d-band center, leading to the enhancement of electroactivity. Notably, the bromine-substituted MOF-Br catalyst displayed remarkable…

The electrochemical CO 2 reduction reaction (CO 2 RR), which utilizes renewable energy to produce carbon-neutral chemicals and fuels, offers a potential pathway toward achieving global carbon neutrality. Cu-based catalysts have gained significant attention in this field due to their unique coupling ability to convert CO 2 into multicarbon products, while maintaining high Faradaic efficiency. However, the CO 2 RR process is complex, involving a multistep proton–electron transfer process that involves intermediates associated with carbon- and oxygen-containing species. Therefore, this work aims to review the recent progress of in situ surface-enhanced Raman spectroscopic (SERS) studies of CO 2 RR on Cu-based catalysts. The possible reaction mechanism of CO 2 RR has been first discussed. In situ SERS studies of CO 2 RR on Cu-based single-crystal electrodes and nanocatalysts with different electronic states, morphologies, and compositions have been reviewed, and various intermediates during CO 2 RR have been captured to clarify the reaction mechanisms and structure–activity…

Hydrogen is considered a crucial clean energy vector to mitigate climate change, but due to the low volumetric energy density of gaseous hydrogen, it is difficult to store hydrogen for many practical applications. Cryogenic sorption-based methods, particularly using metal–organic frameworks (MOFs), have been considered as viable solutions to enhance the deliverable capacity of stored hydrogen, and among the many available MOFs, those with rht topology have demonstrated exceptional capacity. MOFs with rht topology are formed by the assembly of supermolecular building blocks (SBBs), but the diversity of SBBs in the literature on rht -MOFs is limited, resulting in an underexplored structural design space. In this study, we designed 380 MOFs made of 20 novel SBBs to investigate the effect of cavity size on hydrogen storage capacity and the underlying structure–property relationships. We performed grand canonical Monte Carlo simulations on 472 rht -MOFs, encompassing both existing and novel structures, to predict hydrogen loadings under cryogenic conditions (77 K/100 bar →160 K/5 bar)…

The relationship between symmetry-breaking charge separation (SB-CS) and null aggregate (NA) formation in molecular dimer complexes is investigated theoretically, with applications mainly to dimers based on PDI chromophores. Both processes derive from null points, which are defined by degeneracies in either the upper or lower adiabatic exciton bands. The Hamiltonian contains intermolecular coupling derived from the interacting molecular transition dipole moments (Coulomb coupling), which gives rise to Frenkel excitons, as well as the coupling between the Frenkel excitons and charge-transfer (CT) excitons, driven by the electron ( t e ) and hole ( t h ) hopping integrals. A recipe for efficient SB-CS is presented, which, beyond the Weller condition─which holds that the solvent-stabilized CT state should appear below the optical gap -includes two additional conditions: the presence of a null point and, just as important, lopsided electron and hole transfer integrals, | t e | ≫ | t h | or | t h | ≫ | t e |. When such conditions are met, the developing charge asymmetry is optimized in…

High Resolution Image Download MS PowerPoint Slide The sensitivity of localized surface plasmon resonance (LSPR) biosensors to a change in the local refractive index (RI) is investigated theoretically. By combining an effective medium theory and a quasistatic theory, analytical expressions for the local RI sensitivity are derived. Electromagnetic simulations show that the expressions can predict the sensitivity well for LSPR biosensors of various sizes and geometries including nanocylinders, nanodisks, nanorods and nanotriangles for both two- and three-layer systems. Like the bulk RI sensitivity, the local RI sensitivity is shown to depend linearly on the resonant wavelength of the biosensors. Other than two parameters used to linearize the dielectric function of the metal core, there are no fitting parameters. Hence, the expressions can be used to predict the local RI sensitivity of LSPR biosensors directly from the resonant wavelength.

We present a novel and straightforward design for a photonic crystal fiber (PCF)-based surface plasmon resonance sensor suitable for a wide range of sensing applications. The sensor’s performance is numerically analyzed using the finite element method implemented in COMSOL Multiphysics software. Our numerical results demonstrate a wavelength sensitivity(WS) of 88,000 nm/RIU and an amplitude sensitivity(AS) of 3136 RIU –1, with a resolution of 1.136 × 10 –6 RIU. The proposed sensor is capable of detecting analytes within the refractive index (RI) range of 1.29–1.44. Additionally, we investigate the sensor’s fabrication tolerance concerning variations in pitch, air-hole diameter, and channel size, and it exhibits good tolerance to these variations. The sensor also demonstrates a high figure of merit of 1517. With its high sensitivity, broad sensing capability, and excellent fabrication tolerance, this sensor is highly versatile for detecting a wide range of analytes, including glucose, cholesterol, and hemoglobin, making it suitable for various biological and biochemical applications.

High Resolution Image Download MS PowerPoint Slide In this article, we propose simple, interpretable machine learning (ML) features aimed at improving the accuracy of ML models in predicting adsorption of gases, such as methane, ethane, propane, krypton, and xenon, in metal–organic frameworks (MOFs). In particular, we introduce energy-based features that incorporate surface energy histograms and radial distribution functions. These features effectively capture spatial variations in interaction energy, thereby improving the predictive capabilities of the ML models. We further extend this approach to predict the adsorption of carbon dioxide and nitrogen in a diverse set of MOFs under ambient conditions by including the Coulombic energy component in the proposed energy-based features. The final ML model combines the energy-based features with geometric characteristics of MOFs and Henry’s law constants. This integration results in significantly increased predictive accuracy of the models, especially within the moderate pressure regime, when compared to that of previous studies. Using…

High Resolution Image Download MS PowerPoint Slide Transient absorption spectroscopy is a powerful technique to study the photoinduced phenomena in a wide range of states from solutions to solid film samples. It was designed and developed based on photoinduced absorption changes or that photoexcitation triggers a chain of reactions with intermediate states or reaction steps with presumably different absorption spectra. However, according to general electromagnetic theory, any change in the absorption properties of a medium is accompanied by a change in the refractive properties. Although this photoinduced change in refractive index has a negligible effect on solution measurements, it may significantly affect the measured response of thin films. In this Perspective paper, we examine why and how the measured responses of films differ from their expected “pure” absorption responses. The effect of photoinduced refractive index change can be concluded and studied by comparing the transmitted and reflected probe light responses. Another discussed aspect is the effect of light interference…

High Resolution Image Download MS PowerPoint Slide Perfluorooctanoic acid (PFOA) is an environmentally prevalent and persistent organic pollutant with toxic and bioaccumulative properties. Despite the known importance of perfluorinated pollutants in the global environment, molecular-level details of the physicochemical behavior of PFOA on aqueous interfaces remain poorly understood. Here, we utilized two surface-specific techniques, vibrational sum frequency generation spectroscopy (SFG) and surface tensiometry, to investigate the pH-induced structural changes of PFOA and octanoic acid (OA) and determined the apparent p K a at the air–water surface. The SFG spectra and surface activity model were investigated over a wide range of pHs. With the surface tension measurements, the surface p K a values for OA and PFOA are determined to be 3.8 ± 0.1 and 2.2 ± 0.2, respectively. These results could provide insights into improved remediation of PFOAs and may impact climate modeling of perfluorinated alkyl chain molecules.

Defects in the crystal structures of metal-organic frameworks (MOFs), whether present intrinsically or introduced via so-called defect engineering, can play strong roles in the properties of MOFs for various applications. Unfortunately, direct experimental detection and characterization of defects in MOFs are very challenging. We show that in many cases, the differences between experimentally observed and computationally predicted water stabilities of MOFs can be used to deduce information on the presence of point defects in real materials. Most computational studies of MOFs consider these materials to be defect-free, and in many cases, the resulting structures are predicted to be hydrophobic. Systematic experimental studies, however, have shown that many MOFs are hydrophilic. We show that the existence of chemically plausible point defects can often account for this discrepancy and use this observation in combination with detailed molecular simulations to assess the impact of local defects and flexibility in a variety of MOFs for which defects had not been considered previously.

Photophysical attributes of semiconductor quantum dots (QDs) are influenced by the presence of undercoordinated ions on their surface, which generate new bands called trap states. These bands are located within the bandgap in II–VI and III–V systems; hence, their photoluminescence and electron transfer properties are also guided by the trap depth and density. Our efforts to understand these aspects are summarized here by taking CdSe and InP QDs as examples. The increase in photoluminescence efficiency in CdSe QDs with an increase in core size is attributed to the decrease in electron trap depth, allowing efficient detrapping of electrons. Stacking faults, another type of defect, is responsible for the enhanced photoluminescence blinking during the asymmetric shell growth of CdS on CdSe QDs. Investigation of photoinduced electron transfer dynamics further establishes deep trap states in InP QDs, compared to shallow trap states in CdSe QDs, and effective charge stabilization in the former.

Understanding the mechanisms of action of fundamental redox processes is of great interest for the development of more active catalysts and materials for energy storage and conversion devices. To gain more insight into those processes, spectroscopic techniques performed in situ and operando are widely used. In this work, we summarize recent advances in in situ and operando UV–vis, infrared (IR), Raman, X-ray absorption spectroscopy (XAS), and X-ray photoelectron spectroscopy (XPS) for energy storage and conversion applications. We then provide an outlook for the use of these techniques, focusing on improving their temporal and spatial resolution and combining multiple techniques in one experiment (i.e., using a multispectroscopy approach). Finally, we provide an overview of the advancements in the use of machine learning in this field and our perspective on its future applications.

High Resolution Image Download MS PowerPoint Slide The increasing demand for ultraviolet light sources in various industries, including security, phototherapy, and sterilization, has spurred research efforts toward discovering new UV phosphors. Herein, we introduce LiY 9 (SiO 4 ) 6 O 2:Pr 3+ as a novel ultraviolet-C (UVC) phosphor, synthesized via the sol–gel technique with varying Pr 3+ concentrations (0, 0.1, 0.5, 1, 1.5, and 2%). For the first time, this study comprehensively describes the emission and excitation spectra, as well as the emission decay kinetics of Pr 3+ ions in LiY 9 (SiO 4 ) 6 O 2 . Two distinct classes of Pr 3+ -emitting centers were identified, denoted as Pr(1) and Pr(2), which replace Y ions at two different lattice sites, 4f and 6h, respectively. Pr 3+ ions at the 4f site exhibit 4f 2 → 4f 2 emission solely, while those at the 6h site emit predominantly in the ultraviolet, 75% of which is in the UVC range. Furthermore, LiY 9 (SiO 4 ) 6 O 2:Pr 3+ excited by laser at a wavelength of 444 nm, both a continuous wave and a pulse, exhibits upconversion emission in…

High Resolution Image Download MS PowerPoint Slide LiNi x Mn y Co z O 2 (NMC) materials are entering commercial lithium-ion batteries although their charging and discharging mechanism and the underlying Li kinetics are still not entirely understood. Li diffusion directly influences charging/discharging times, maximum capacities, stress formation (electrode stability), and possible side reactions. In order to measure intrinsic properties, samples without binders and conductive agents have to be investigated. The present work reports on the determination of Li diffusivities in additive-free 250 μm thick NMC111 ( x = y = z = 0.33) bulk electrodes, which were produced by ball milling, pressing, and sintering. The Li diffusivities were determined close to the delithiation onset. Different methods were applied: electrochemical impedance spectroscopy (EIS), potentiostatic intermitted titration technique (PITT), and tracer diffusion experiments using stable 6 Li isotopes and secondary ion mass spectrometry (SIMS). The obtained diffusivities from the three different techniques are in…

High Resolution Image Download MS PowerPoint Slide Global water scarcity fuels the search for innovative mitigation strategies for atmospheric water harvesting. Among these approaches, metal–organic frameworks (MOFs) have emerged as promising; however, the intricate atomic details and physical principles of the process of water adsorption are still unresolved. We deployed simulations to explore the mechanism of atmospheric water harvesting using MOF-303. Computer simulations reveal uptake capacity under varying humidity, mirroring the experiments. Molecular details afforded by simulations allow for the investigation of thermodynamic and dynamic factors governing the adsorption process. Our analysis revealed that the pyrazole group in the linker emerges as a pivotal water-binding site, enabling the nucleation of dense vapor to form unsaturated clusters. The unsaturated clusters formed inside the cavities were observed to grow to condense when removed from the framework, leading to facile release. This study elucidates the fundamental principles driving this process, guiding the…

Computation has long proven useful in understanding heterogeneous catalysts and rationalizing experimental findings. However, computational design with experimental validation requires somewhat different approaches and has proven more difficult. In recent years, there have been increasing successes in such computational design with experimental validation. In this Perspective, we discuss some of these recent successes and the methodologies used. We also discuss various design strategies more broadly, as well as approximations to consider and pitfalls to try to avoid when designing for experiment. Overall, computation can be a powerful and efficient tool in guiding catalyst design but must be combined with a strong fundamental understanding of catalysis science to be most effective in terms of both choosing the design methodology and choosing which materials to pursue experimentally.

Developing highly efficient bifunctional electrocatalysts made from abundant metals is key to unlocking the large-scale, sustainable production of hydrogen through water splitting. LDH (layered double hydroxide) materials (thanks to the layered structure and the high surface area) are hot for electrocatalysis due to their unique electron transport properties. Here, in this work, we report the formation of CoNi-LDH-derived CoNiSe 2 nanosheets via a simple hydrothermal technique subjected to water electrolysis in 1 M KOH. The CoNiSe 2 demands a lesser overpotential of 295 and 214 mV in alkaline conditions to reach the 50 mA cm –2 current density toward OER and HER, respectively. Moreover, after selenization, the charge accumulated and surface-active sites are hiked ∼23.6- and 29-fold than the pristine CoNiSe 2, respectively. Likely, high performance is owing to the repulsion between the metal d-band center and the 3p orbitals of Se and the adsorbed O atom (associated O p-band centers). Furthermore, CoNiSe 2 exhibits higher TOF values of 0.3939 and 0.7662 × 10 –3 s –1 toward the OER…

High Resolution Image Download MS PowerPoint Slide Raman spectroscopy is an important characterization tool with diverse applications in many areas of research. We propose a machine learning (ML) method for predicting polarizabilities with the goal of providing Raman spectra from molecular dynamics trajectories at a reduced computational cost. A linear-response model is used as a first step, and symmetry-adapted ML is employed for the higher-order contributions as a second step. We investigate the performance of the approach for several systems, including molecules and extended solids. The method can reduce the training-set sizes required for accurate dielectric properties and Raman spectra in comparison to a single-step ML approach.

Recent developments in machine learning interatomic potentials (MLIPs) have empowered even non-experts in machine learning to train MLIPs for accelerating materials simulations. However, the current literature lacks clear standards for documenting the use of MLIPs, which hinders the reproducibility and independent evaluation of the presented results. In this perspective, we aim to provide guidance on best practices for documenting MLIP use while walking the reader through the development and deployment of MLIPs including hardware and software requirements, generating training data, training models, validating predictions, and MLIP inference. We also suggest useful plotting practices and analyses to validate and boost confidence in the deployed models. Finally, we provide a step-by-step checklist for practitioners to use directly before publication to standardize the information to be reported. Overall, we hope that our work will encourage reliable and reproducible use of these MLIPs, which will accelerate their ability to make a positive impact in various disciplines including…

In recent years, the concept of entropy stabilization has led to increased research in “high-entropy materials”. These compounds incorporate multiple metals into a single crystalline phase, resulting in interactions between them that offer novel and unexpected properties. Here, we report on the surface evolution and entropy changes of the high-entropy spinel oxide (HEO) Zn(CrMnFeCoNi) 2 O 4 upon its use as an electrocatalyst for the oxygen evolution reaction (OER). It was found that electrochemical cycling of this material results in surface reconstruction accompanied by induced leaching of surface Zn from the tetrahedral sites. The formation of a completely new metal (oxy)hydroxide Zn 2 Cr 1.5 Mn 2 Fe 1 Co 2 Ni 1.5 O x H y is observed at the surface, leading to an increase in surface entropy over the pristine spinel HEOs. The newly formed surface exhibits improved OER catalytic performance through the adsorbate evolution mechanism (AEM). Removing any one of the cations from this HEO results in a significant decrease in the OER performance. This shows that the electrochemical…

The high capacitive performance of MXenes in acidic electrolytes has made them potential electrode materials for supercapacitors. In this study, we conducted a structural analysis of MXene surface functionalizations by identifying the surface group distribution pattern and revealed the energy storage process of MXene surface chemistry by combining a complete Pourbaix stability diagram and density functional theory (DFT) calculations. The Pourbaix diagram indicated that pH controls the surface termination; an acidic pH generates favorable initial surfaces of MXenes with a specific distribution of functional groups (10 hydroxyls with respect to 18 total locations for the selected surface unit). Using this, we report the charging and uncharging process of MXenes with transitions of surface oxygenic groups (−OH and -O) via hydrogen ion adsorption and desorption on the MXene surface. Our results demonstrated that transitions of surface functionalizations contribute to comparable pseudocapacitance and electrostatic capacitance for MXenes. These findings provide insights into understanding…

Two-dimensional (2D) materials have attracted much attention because of their atomic-thin thickness and unique properties, such as high binding energy, tunable band gap, and new electronic degrees of freedom (valleytronics). They have found many applications in microelectronics, nanophotonics, nano energy, and so on. In the past decade, various 2D devices have been developed, including field effect transistor (FET), nano light source, photodetector, supercapacitors, etc. However, the application of 2D materials is still limited by their intrinsic properties, e.g., the low carrier concentration, high contact resistance at heterogeneous interface, and the challenge of thickness control in transition metal dichalcogenides. It remains an alluring perspective to tune the geometry and electronic and photonic properties of 2D materials on demand. Specifically, laser modification is a contactless processing technique with high accuracy, high efficiency, and versatility due to the flexibility to manipulate light at high spatiotemporal resolution. Here, we review the light–matter interaction…

The recent high-pressure experimental discovery of superconductivity in (La,Y)H$_{10}$, (La,Ce)H$_{9}$, (La,Ce)H$_{10}$, (Y,Ce)H$_{9}$, and (La,Nd)H$_{10}$ shows that the ternary rare-earth clathrate hydride can be promising candidate for high-temperature superconductor. In this work, we theoretically demonstrate that the combination of actinide-metal thorium (Th) and rare-earth-metal lanthanum (La) with hydrogen can also form some ternary hydrides with cage-like structures to be stable at 200 GPa. Using the evolutionary algorithms combined with the first-principles calculations, we have predicted the pressure-dependent ternary phase diagram of La$_{x}$Th$_{y}$H$_{z}$, particularly including the case of (La$_{1-x}$Th$_{x}$)H$_{n}$ [or designated as (La,Th)H$_{n}$ for simplicity]. Our calculations show that the hydrogen-rich phases such as (La,Th)H$_{9}$ (only including $P\bar{6}m2$-LaThH$_{18}$) and (La,Th)H$_{10}$ (including $I4/mmm$-La$_{3}$ThH$_{40}$, $R\bar{3}m$-LaThH$_{20}$, and $I4/mmm$-LaTh$_{3}$H$_{40}$) with H$_{29}$ and H$_{32}$ cages can be thermodynamically stable below…

Molecular doping of semiconducting polymers has emerged as a prominent research topic in the field of organic electronics, with new dopant molecules introduced regularly. FeCl 3 has gained attention as a p-type dopant due to its low cost, availability, ability to dope high ionization energy copolymers, and its use as a dopant that can be used with anion exchange. Here, we use a combination of UV–vis–NIR spectroscopy, four-probe sheet resistance measurements, and X-ray absorption near-edge structure (XANES) spectroscopy to perform lifetime measurements to assess the stability of the doped polymers over time, which is crucial for evaluating the long-term performance and reliability of the doped films. We used gas chromatography–mass spectrometry (GCMS) to prove that FeCl 3 can cause radical side reactions that damage the conjugated polymer backbone, leading to the degradation of the electronic properties. The rate of this degradation is orders of magnitude higher when the film is exposed to air. Anion exchange doping can reduce the [FeCl 4 ] − concentration, but does not necessarily…

In this work, graphitic carbon nitride (g-C 3 N 4 ) was doped with boron by thermal treatment with NaBH 4 . We have shown that the morphology of the modified polymer gradually changes from graphitic-like to amorphous, with increasing amounts of NaBH 4 used for annealing. On the other hand, the boron doping has a very small influence on the band gap energy, as well as on the positions of the valence and conduction band edges of the polymer, but strongly improves the activity of g-C 3 N 4 in the photocatalytic reduction of oxygen and degradation of methyl orange (8-fold increase of the degradation rate constant with respect to that of pure g-C 3 N 4 ). The enhancement of the photocatalytic properties was explained by the increased rate of charge transport, both in the polymer plane and across the film, due to formation of N–B–N bonds between the adjacent heptazine units and the interlayer Coulomb interactions. The best photocatalytic activity was obtained for samples prepared from a mixture of g-C 3 N 4 and NaBH 4 at a moderate weight ratio (4:1), while increased amounts of NaBH 4 led…

Recent advancements in materials science have resulted in impressive electrode materials; however, their practical implementation is often limited by complex and resource-intensive synthesis processes including high-temperature requirements, long synthesis times, and low yield. To advance the field of energy storage, it is crucial to develop synthesis methods that minimize both energy and time consumption. In this study, we employed a low-temperature, time-efficient, and cost-effective synthesis technique for fabricating high-performance electrode materials. Herein, a MnCo 2 O 4 /multiwalled carbon nanotube (MWCNT) (MCOC) nanocomposite is synthesized via a low-temperature coprecipitation approach. The effect of MWCNTs on the electrochemical properties of the nanocomposites has been studied. The synthesized MCOC1 sample (0.99MnCo 2 O 4 + 0.01MWCNT) demonstrated enhanced electrochemical characteristics, exhibiting a specific capacitance of 540 Fg – 1 at 0.5 Ag – 1 and good cyclic stability with 87.91% capacitance retention over 5000 cycles at 8 Ag – 1, attributed to its higher surface…

High-entropy alloys (HEAs), characterized as compositionally complex solid solutions with five or more metal elements, have emerged as a novel class of catalytic materials with unique attributes. Because of the remarkable diversity of multielement sites or site ensembles stabilized by configurational entropy, human exploration of the multidimensional design space of HEAs presents a formidable challenge, necessitating an efficient, computational and data-driven strategy over traditional trial-and-error experimentation or physics-based modeling. Leveraging deep learning interatomic potentials for large-scale molecular simulations and pretrained machine learning models of surface reactivity, our approach effectively rationalizes the enhanced activity of a previously synthesized PdCuPtNiCo HEA nanoparticle system for electrochemical oxygen reduction, as corroborated by experimental observations. We contend that this framework deepens our fundamental understanding of the surface reactivity of high-entropy materials and fosters the accelerated development and synthesis of monodisperse HEA…

Vertical stacking of two semiconducting monolayers is an effective way to improve the optoelectronic performance of individual monolayers. Employing first-principles calculations, MoSi 2 P 4 /BAs heterobilayers with six stacking configurations (AA1 ∼ AA6) are investigated. In particular, the electronic and optical properties of the AA2 stacking configuration are explored in depth due to the relatively high stabilities. The AA2 configuration is predicted to be a direct semiconductor with a moderate gap at the G 0 W 0 level. It also exhibits strong optical absorption for near-infrared and visible lights, which is significantly better than that of the isolated MoSi 2 P 4 monolayer. Based on G 0 W 0 +BSE calculations, the light absorbance coefficients of the AA2 configuration can be larger than 10 7 cm –1 in the near-infrared-visible light range. More interestingly, a type-II band alignment and an advantageous built-in electric field are formed in the AA2 stacking, which facilitates the effective separation of intralayer photogenerated electron–hole pairs, thus forming an indirect…

High Resolution Image Download MS PowerPoint Slide Mg nanoparticles are an emerging plasmonic material due to Mg’s abundance and ability to sustain size- and shape-dependent localized surface plasmon resonances across a broad range of wavelengths from the ultraviolet to the near infrared. However, Mg nanoparticles are colloidally unstable due to their tendency to aggregate and sediment. Nanoparticle aggregation can be inhibited by the addition of capping agents that impart surface charges or steric repulsion. Here, we report that the common capping agents poly(vinyl) pyrrolidone (PVP), polyethylene glycol (PEG), cetyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS) interact differently and have varied effects on the aggregation and colloidal stability of Mg nanoparticles. Nanoparticles synthesized in the presence of PVP showed improvements in colloidal stability and reduced aggregation, as observed by electron microscopy and optical spectroscopy. The binding of PVP was confirmed through infrared and X-ray photoelectron spectroscopy. The influence of PVP on the…

Capacitive deionization (CDI) technology is a promising desalination technology with the advantages of low energy consumption, high water recovery, and environmental friendliness. Hierarchical porous carbons (HPCs) have attracted intense interest due to their excellent physicochemical and electrochemical properties. In this work, hierarchical porous biochar materials were prepared through a direct carbonization method using natural porous biomass including lotus petiole (LP), sunflower plate (SP), and lotus seedpod (LS). The effects of pore structures, surface properties, and electrochemical properties of these biochars on the desalination performance were investigated. The results showed that the biochar prepared from SP (SPC) had a more suitable aperture structure, better surface wettability, higher surface charge, and larger specific capacitance than those of other biochars prepared from LP and LS (LPC and LSC), which resulted in better desalination performance (9.24 mg·g –1 ) and charge efficiency (77%) of SPC. The desalination processes of the three biochars all conformed to…

The sensing properties of WO 3 -based gas sensors were evaluated at an operating temperature of 150 °C in the presence of different volatile organic compounds (VOCs). Simultaneously to the sensing tests, operando diffuse-reflectance infrared Fourier transform spectra were acquired. Remarkably, no CO 2 generation was observed under gas exposure for any of the target VOCs. Catalytic combustion properties of the WO 3 toward acetone and ethanol at temperatures from 150 to 400 °C, both in dry and humid atmospheres, were additionally performed. Such measurements confirmed that no combustion occurred for ethanol (up to at least 300 °C) while it became detectable for acetone only starting from 250 °C. The reaction products are acetaldehyde and acetate in the case of ethanol exposure and acetate and formate in the case of acetone exposure. The oxidation catalytic effect of WO 3 was confirmed for both toluene, where benzaldehyde and benzoate modes were observed, and acetylene (where acetaldehyde and ethenol were detected). The systematic absence of CO 2 as a product and the identification of…

High Resolution Image Download MS PowerPoint Slide In this study, we explore the impact of halogen functionalization on the photophysical properties of the commonly used organic light-emitting diode (OLED) host material, 1,3-bis( N -carbazolyl)benzene (mCP). Derivatives with different numbers and types of halogen substituents on mCP were synthesized. By measuring steady-state and transient photoluminescence at 6 K, we study the impact of the type, number, and position of the halogens on the intersystem crossing and phosphorescence rates of the compounds. In particular, the functionalization of mCP with 5 bromine atoms results in a significant increase of the intersystem crossing rate by a factor of 300 to a value of (1.5 ± 0.1) × 10 10 s –1, and the phosphorescence rate increases by 2 orders of magnitude. We find that the singlet radiative decay rate is not significantly modified in any of the studied compounds. In the second part of the paper, we describe the influence of these compounds on the reverse intersystem crossing of the…

Scaling and Brøndsted-Evans-Polanai (BEP) relations have proven immensely powerful in catalysis theory. The relations provide an understanding of the Sabatier principle in a quantitative fashion, such that we can calculate the adsorption energy that most optimally compromises between a low reaction barrier and a not too strong absorption. Scaling and BEP relations are usually mapped out for pure metal surfaces and it is not directly clear how they translate to complex alloy surfaces, e.g. high-entropy alloys (HEAs). The scaling relation between *OH and *OOH is one of the most studied and best understood. Generally, both *OH and *OOH adsorb on a single surface atom, so HEAs do not change the established scaling relation, but rather widen the distribution of available adsorption energies. The situation can be different for reactions at multi-atom surface sites. The reaction between O* and *CO to form CO2 interact with more surface atoms at the initial state compared to the transition state, so for a given reaction energy, HEAs allow for lower activation energies than pure metals. The…

Three-dimensional (3D) carbon allotropes have been extensively researched for their potential new applications in batteries, gas separation, and electronic devices. Therefore, this current study investigates the suitability of 3D porous HZGM-42 for efficient hydrogen storage due to its enlarged pore size, mechanical rigidity, and the stability of decorating lithium (Li) atoms on the channels by a polarization mechanism, using state-of-the-art theoretical simulations. Our findings demonstrate that 3D HZGM-42 is an ideal material with high thermal and thermodynamic stability, high Li-binding strength (−2.92 eV), hydrogenation adsorption in the appropriate range (−0.233 eV/H 2 ), theoretical H 2 storage capacity (6.08 wt %), and very-low activation barriers (0.018–0.026 eV) for H 2 migration. Furthermore, the exploration of the effect of equilibrium pressure on the van’t Hoff desorption temperature of the HZGM-42 system shows that, at 100 Atm, the dehydrogenation temperature reaches standard conditions (243 K) with a desorption time of 67 ns. The effectiveness of hydrogen…

High Resolution Image Download MS PowerPoint Slide Carbon dioxide reduction reaction (CO 2 RR) is a promising method for converting CO 2 into value-added products. CO 2 RR over single-atom catalysts (SACs) is widely known to result in chemical compounds such as carbon monoxide and formic acid that contain only one carbon atom (C1). Indeed, at least two active sites are commonly believed to be required for C–C coupling to synthesize compounds, such as ethanol and propylene (C 2+ ), from CO 2 . However, experimental evidence suggests that iron phthalocyanine (PcFe), which possesses only a single metal center, can produce a trace amount of C 2+ products. To the best of our knowledge, the mechanism by which C 2+ products are formed over a SAC such as PcFe is still unknown. Using density functional theory (DFT), we analyzed the mechanism of the CO 2 RR to C1 and C 2+ products over PcFe. Due to the high concentration of bicarbonate at pH 7, CO 2 RR competes with HCO 3 – reduction. Our computations indicate that bicarbonate reduction is significantly more favorable. However, the rate of…

High Resolution Image Download MS PowerPoint Slide MXenes are two-dimensional (2D) materials with versatile applications in optoelectronics, batteries, and catalysis. To unlock their full potential, it is crucial to characterize MXene interfaces and intercalated species in more detail than is currently possible with conventional optical spectroscopies. Here, we combine ultra-broadband ellipsometry and transmission spectroscopy from the mid-infrared (IR) to the deep-ultraviolet (UV) to probe quantitatively the composition, structure, transport, and optical properties of spray-coated Ti 3 C 2 T x MXene thin films with varying material properties. We find film thickness heterogeneity and surface roughness in the low-nanometer range as well as depth-dependent conductivity properties, which we quantify with a graded Drude model. The optically determined sheet resistance is confirmed by four-point probe measurements. Furthermore, we employ density-functional-theory calculations to assign the observed absorption bands in the MXene dielectric function to various interband transitions from…

High Resolution Image Download MS PowerPoint Slide In the field of electrochemical CO 2 reduction, both continuum models and molecular dynamics (MD) models have been used to understand the electric double layer (EDL). MD often focuses on the region within a few nm of the electrode, while continuum models can span up to the device level (cm). Still, both methods model the EDL, and for a cohesive picture of the CO 2 electrolysis system, the two methods should agree in the regions where they overlap length scales. To this end, we make a direct comparison between state-of-the-art continuum models and classical MD simulations under the conditions of CO 2 reduction on a Ag electrode. For continuum modeling, this includes the Poisson–Nernst–Planck formulation with steric (finite ion size) effects, and in MD the electrode is modeled with the constant potential method. The comparison yields numerous differences between the two modeling methods. MD shows cations forming two adsorbed layers, including a fully hydrated outer layer and a partial hydration layer closer to the electrode surface.…

The Urbach energy as a measure of energetic disorder is an important characteristic of semiconductors to evaluate their optoelectronic functionality. However, discrepancies occur in Urbach energy values E U determined via different measurement and analysis methods, whose origin of a profound understanding is still missing. To reliably analyze the origin of such discrepancies, we recorded quasi-simultaneously temperature-dependent absorption and photoluminescence (PL) spectra of halide perovskite (MAPbI 3 ) thin-film and single-crystal samples. Performing profound Urbach analyses in an extended energy range down to 0.2 eV below the bandgap, we find energy-range-dependent exaggeration effects on Urbach energy values to be only present in the near bandgap region (∼0.02 eV below the bandgap), where non-Urbach absorption states start to contribute. Besides that, generally lower E U values and a lower temperature-dependence of E U are obtained from PL than from absorption, which originates from the sensitivity of PL for sites with lower energetic disorder and/or higher phonon energies in…

The ever-growing environmental concern has yielded the electrocatalytic carbon dioxide reduction (eCO 2 R) center of research attention, as it offers a possible pathway to achieve net-zero carbon emission and realize a post-fossil-fuel society. The production of multicarbon (C 2+ ) species with higher energy density is more desirable but unfortunately presents a greater challenge. Other than the catalyst itself, the electrolyte has also been demonstrated to exhibit nontrivial impacts on eCO 2 R, a systematic understanding on the effect of which therefore remains vital. In this Review, we thoroughly discussed the influence that electrolytes might induce on eCO 2 R from three perspectives, namely, pH, cations, and anions. Both experimental and theoretical efforts are included, along with the hypothesis on the fundamental working mechanism. We also highlighted the challenges associated with understanding and harnessing the electrolyte effect, as well as theoretical modeling and machine learning as interesting directions worthy of further research and exploration. We believe that this…

High Resolution Image Download MS PowerPoint Slide Inversion analysis of transient absorption data to capture the photoexcited charge carrier population rate dynamics is a powerful technique for extracting realistic lifetimes and identifying recombination pathways. However, for highly scattering samples such as Cu 2 O nanoparticles (NPs) with associated dielectric Mie scattering, the scattering leads to an inaccurate measure of the excited photocarrier. This work studies methods to correct for the scattering to generalize the use of inversion analysis and provide secondary information about the nature of the scattering NPs. Scattering profiles of semitransparent disks containing Cu 2 O NPs with different shapes and sizes are measured to demonstrate that the inclusion of scattering in analysis reduces the photoexcited carrier density by 1 order of magnitude. It is found that the photocarrier density response is affected by shape rather than size. A Fourier transform of the scattering profiles produces a distribution of length scales within the sample characteristic of the mean…

The photoconversion of CO 2 to hydrocarbons is a sustainable route for its transformation into value-added compounds, which is crucial to mitigating energy and climate crises. CuPt nanoparticles on TiO 2 surfaces have been reported to show promising photoconversion efficiencies. For further progress, a mechanistic understanding of the catalytic properties of these CuPt/TiO 2 systems is vital. Here, we employ ab initio calculations, machine learning, and photocatalysis experiments to understand the photocatalytic reduction of CO 2 on CuPt/TiO 2 . We explore the configurational space of the CO 2 @CuPt/TiO 2 systems and examine their structures and energetics. We find that the CuPt/TiO 2 interface plays a key role in determining CO 2 activation and, thus, the conversion to hydrocarbons. The interface stabilizes *CO and other intermediates containing CH groups, thus facilitating a higher activity and selectivity for methane. A bias-corrected machine-learning interatomic potential trained on density functional theory data enables the efficient exploration of the potential energy surfaces…

Defect states and polarons of photocatalytic semiconductors play important roles by notably influencing carrier mobility and reactivity. Extensive studies have focused on identifying defect states and the physical properties of polarons, as well as their consequential impact on catalytic efficiency. This Featured Article summarizes recent investigations of defects and polarons using time-resolved spectroscopies in photocatalytic semiconductors. These include transient infrared absorption–excitation energy scanning spectroscopy to identify defect states within the bandgap of photocatalytic materials such as anatase and rutile TiO 2, ZnO, and CdS and time-resolved spectroscopic studies on the temporal evolution of photogenerated electron and hole polarons within these semiconductors. Finally, we address the current challenges in the study of defects and polarons.

Efficiently separating sulfur hexafluoride/nitrogen (SF 6 /N 2 ) poses an urgent challenge. Four covalent organic frameworks (COFs) (Re % > 80%) with greater performance in SF 6 /N 2 separation experiment were selected from the CURATED database by high-throughput screening in this paper. XGB was selected among four machine learning models (SVM, RF, GBRT, and XGB) and this model had good fitting effects in terms of both regeneration (Re %, R 2 = 0.809) and ln( S ads ). Relative importance analyses of XGB described that porosity and infinite dilution heat are the most key features for Re % and ln( S ads ). The binding energy, charge density difference, Bader charge, and independent gradient model based on Hirshfeld partition (IGMH) analysis were all calculated to investigate the adsorption mechanisms. GCMC simulations combined with density functional theory calculations revealed that COF-638 exhibited an excellent SF 6 /N 2 separation performance. The probability distribution diagram of the center of mass illustrates the adsorption sites of SF 6 in coadsorption.

Water adsorption isotherms from 25 to 125 °C were measured for three metal–organic frameworks (MOFs), MOF-303, MOF-LA2-1, and MIL-100(Fe), which are frequently studied for water harvesting applications. The results show how the step in the water adsorption isotherm varies as a function of temperature and detail the combination of pressure and temperature necessary to remove adsorbed water. Furthermore, isobaric–isothermal Gibbs ensemble Monte Carlo simulations performed for MOF-303 shed light on the change in occupation numbers of the different known water adsorption sites with increasing temperature. Additionally, the diffusion rates of water through these materials were measured using concentration swing frequency response, and micropore diffusion was identified as the controlling mechanism. The Darken relation was used to show the dependence of the diffusion rate on the concentration and the impact of the adsorption isotherm slope. The adsorption of water on MOF-LA2-1 is faster than that on MIL-100(Fe). These data show that MOF-LA2-1 with its high-water adsorption capacity, quick…

High Resolution Image Download MS PowerPoint Slide Electron microscopy, while reliable, is an expensive, slow, and inefficient technique for thorough size distribution characterization of both monodisperse and polydisperse colloidal nanoparticles. If rapid in situ characterization of colloid samples is to be achieved, a different approach, based on fast, widely accessible, and inexpensive optical measurements such as UV–vis spectroscopy in combination with spectral interpretation related to Mie scattering theory, is needed. In this article, we present a tandem deep neural network (DNN) for the size distribution and concentration prediction of close to spherical silver colloidal nanoparticle batches synthesized via the seeded-growth method. The first DNN identified the dipole component of the localized surface plasmon resonance, and the second one determined the size distribution from the isolated spectral component. The training data was engineered to be bias-free and generated numerically. High prediction accuracy with root-mean-square percentage error of mean size down to 1.2% was…

Single molecule magnets (SMMs) constitute a pivotal class of nanoscale molecular magnets with promising potential across various domains such as high-density information storage, quantum computing, and spin electron devices. Among these, lanthanide-based SMMs have garnered significant attention in recent research due to their distinctive magnetic and coordination properties, offering prospects for substantial advancements in information storage technologies. Over the past three decades, considerable efforts have been directed toward developing novel SMMs characterized by substantial anisotropy barrier and blocking temperature, leading to significant strides in the field. This perspective delves into the latest developments in the structure and performance of lanthanide SMMs, providing valuable insights into optimizing their functionality. The pivotal roles of ligands and central atoms in modulating the anisotropy of SMMs are emphasized alongside strategies to augment magnetic anisotropy and explore their potential surface applications. Additionally, this perspective explores the…

The ligand exchange of perovskite nanocrystals is crucial for achieving highly efficient and stable light-emitting diodes (PeLEDs). Here, we report the shape transformation of CsPbBr 3 nanocrystals from dodecahedron to cube during the ligand exchange using dimethylammonium bromide (DDAB). The shape transformation is thoroughly investigated by experimental characterization and density functional theory calculations, revealing the surface selective etching effect of DDAB. Among the {002}, {220}, and {112} facets in dodecahedron CsPbBr 3 nanocrystals, DDAB has the highest binding energy with the (220) facet, which accounts for surface selectivity and shape transformation. PeLEDs based on DDAB-capped CsPbBr 3 nanocrystals exhibit average and maximum external quantum efficiencies (EQE) of 14.6 and 18.5%, respectively. Therefore, the ligand exchange using DDAB is an effective strategy for the production of high-quality perovskite nanocrystals for optoelectronic applications.

The contributions to the piezoelectric coefficient d 33 from the intrinsic contribution, reversible low-field domain wall vibration, and irreversible domain switching and displacement of domain walls have been quantitatively investigated in potassium sodium niobate (KNN) ceramics with different phase structures. By measuring the piezoelectric coefficient at a large field and the piezoelectric hysteresis under subswitching conditions following Rayleigh relations, the intrinsic/extrinsic and reversible/irreversible piezoelectric responses are studied to understand the role of different phase boundaries in enhancing the piezoelectricity. This lattice contribution, reversible domain wall vibration, and irreversible contributions are strongly dependent on the crystal and domain structures of the examined ceramics. The intrinsic, reversible extrinsic, and irreversible extrinsic piezoelectric coefficients can both be enhanced in the phase instability regime for KNN-based ceramics. With respect to the intrinsic piezoelectric contribution ratio, ceramics with an orthorhombic-tetragonal (O-T)…

The electrochemical reduction of nitrate to ammonia is considered a feasible strategy to address the imbalance of the global nitrogen cycle by eliminating N-containing pollutants in wastewater while producing ammonia in a sustainable way. In this work, we systematically investigate the reduction of nitrate to ammonia on p-block indium (In), noble metal ruthenium (Ru), and their alloys (InRu 3, In 3 Ru). We found that pure In and Ru candidates exhibit various performances for nitrate reduction with low limiting potentials for the potential-determining step of −0.31 V and −0.14 V, respectively. However, the incorporation of In into Ru to create alloys leads to excellent activity for the reduction of nitrate to ammonia. Ammonia production on InRu 3 and In 3 Ru alloys demonstrates higher catalytic activity and selectivity as the byproducts of NO 2 and NO can be inhibited, while the parasitic hydrogen evolution reaction (HER) can also be significantly suppressed. Our work not only proposes efficient electrocatalysts for nitrate reduction but also provides a new strategy for the rational…

Knowledge of the concentration of alkali cations in an electrochemical double layer is essential for interpreting and leveraging cation effects in electrocatalysis. We systematically study the concentration profiles of four alkali cations (Li +, Na +, K +, and Cs + ) at a Ag(111)-aqueous interface. Using classical molecular dynamics, the potential of mean force (PMF) of cations approaching a metal surface was computed and decomposed into contributions from the solvent and the metal surface. We find that hydration shell deformations contribute importantly to the free energy of cations near the electrode. Cations with larger ionic radii and looser hydration shells experience less solvation loss and less short-range Coulombic screening, which enable them to adsorb more strongly to a negatively charged surface (Cs + > K + > Na + > Li + ). We compute the non-Faradaic electrosorption valency and the interfacial capacitance and show that these experimentally relevant quantities encode the relative concentration of the adsorbed alkali cations of different sizes, but not the spatial…

The carbonation process of C–S–H in cement-based materials has the potential to capture carbon dioxide from the atmosphere. However, understanding this process has been hindered by the amorphous nature of C–S–H and the various pore structures that result from carbonation. To better understand this phenomenon, we have carefully synthesized and carbonated C–S–H with 100% CO 2 for 24 h and then investigated it using solid-state 29 Si NMR and 1 H relaxometry under relative humidity (RH) conditions. We found that the degree of collapse and reconstruction of the silicate chain structure during carbonation strongly depends on the Ca/Si ratio of the C–S–H and the RH conditions. The polymorphism of carbonates resulting from carbonation also varies in their parameters. The collapse of the chain structure produces bridging silicate structures like amorphous glass, resulting in the development of large-sized pores filling with water. Interlayer, gel pore, and capillary pore water in C–S–H can be determined by 1 H NMR relaxometry using spin–spin relaxation time ( T 2 ). Careful T 2 analyses of…

Applying MXenes, a recently discovered class of two-dimensional materials, for detection of nucleobases has been attracting much interest due to their excellence in electronic and optical properties. On the other hand, owing to the importance of nucleobase detection in DNA sequencing, testing of gene-related disease, and disease treatment, the study of MXenes in this field appears to be promising. This work focuses on the study of potential detection of nucleobases by mixed functionalization of titanium carbide MXene (Ti 3 C 2 ) with oxygen and sulfur atoms, by employing first-principles calculations. Intrinsic mechanisms of nucleobase adsorption and the corresponding changes in the electronic properties of Ti 3 C 2 OS are studied through density of states, charge analysis, work function, and electrostatic potential calculations. Van der Waals-induced simulations reveal the adsorption energy of adenine (−0.77 eV), cytosine (−0.53 eV), guanine (−0.82 eV), thymine (−0.51 eV), and uracil (−0.62 eV) on Ti 3 C 2 OS. The calculated work function before and after the adsorption process…

The search for two-dimensional (2D) materials with interesting topological properties is still attracting growing interest, as they offer exotic physical phenomena. Recently, the emergent 2D MA 2 Z 4 has been gaining attention because it exhibits versatile properties due to its tunable elemental components M, A, and Z. In this study, an exhaustive search coupled with first-principles calculations was performed to investigate 30 MA 2 Z 4 (M is Group IV transition metals Ti, Zr, or Hf; A is Si or Ge; and Z is pnictogens N, P, As, Sb, or Bi) monolayers under two crystal phases called T-phase and H-phase, totaling to 60 structures. Ground state energy calculations revealed that all materials energetically prefer the T-phase. Remarkably, the Z 2 topological invariant calculated under hybrid functional HSE06 reveals five MA 2 Z 4 monolayers (TiSi 2 Bi 4, ZrGe 2 P 4, ZrGe 2 As 4, HfSi 2 As 4, and HfGe 2 As 4 ) to have nontrivial topology. This topological phase transition was driven by the spin–orbit coupling resulting in the splitting of the d z 2 orbital of transition metal elements and…

A visible-light-responsive chiral mesoporous TiO 2 photocatalyst was employed for the photodegradation of tetracycline in seawater to avoid the potential biotoxicity of nanophotocatalysts. Compared with achiral mesoporous TiO 2, the key structural parameters, including Ti 3+ and oxygen vacancies, affecting the visible-light response and activity of the chiral mesoporous TiO 2 photocatalyst were clarified. The influence of salt ions in seawater on photocatalytic degradation was systematically explored to reveal the photodegradation mechanisms in complex seawater. Based on the results of radical-trapping experiments and electron spin resonance spectroscopy, the active species generated by photocatalysts excited by visible light were the same in freshwater and seawater. However, the results of density functional theory calculations and the analysis of intermediate products showed that free radicals ( • OH and • O 2 – ) could not efficiently compete with Mg 2+ and Ca 2+ in seawater and therefore could not overcome the interference of salt ions to attack the nitrogen atom in tetracycline…

Al-rich 60Al 2 O 3 –40SiO 2 glass is a candidate for technological applications in electronic and optical devices. Though the amorphous structure of the glass has been studied using solid-state NMR and simulation approaches, the atomic and electronic structure have not been fully revealed. Solid-state 27 Al NMR spectra reflect the 27 Al environment, though a comprehensive understanding of the spectra and local structure is challenging when interpreting the broadened peak shapes of the amorphous state. Here, an accurate atomic structure of 60Al 2 O 3 –40SiO 2 glass was modeled using ab initio molecular dynamics (AIMD) simulations containing 418 atoms and employing the melt-quenching route with 15 K/ps. This simulation approach reproduced X-ray diffraction data better than classical molecular dynamics (CMD) simulations. The structure of the polyhedra formed by O bonded to Al was quantitatively analyzed by evaluating bond-angle distributions and the degree of symmetry using spherical harmonic functions. The relationship between chemical shifts and charge-balancing mechanisms was…

High Resolution Image Download MS PowerPoint Slide Hydrogen adatoms are involved in many reactions catalyzed by Transition Metal (TM) surfaces, such as the Haber–Bosch process or the reverse water gas shift reaction, key to our modern society. Any rational improvement on such a catalyst requires an atomistic knowledge of the metal↔hydrogen interaction, only attainable from first-principles calculations on suited, realistic models. The present thorough density functional theory study evaluates such H interaction at a low coverage on most stable surfaces of bcc, fcc, and hcp TMs. These are (001), (011), and (111) for bcc and fcc TMs and (0001), (101̅0), and (112̅0) for hcp, covering 27 TMs and 81 different TM surfaces in total. In general terms, the results validate, while expanding, previous assessments, revealing that TM surfaces can be divided into two main groups, one in the majority where H 2 would be thermodynamically driven to dissociate into H adatoms, located at heights of ∼0.5 or ∼1.0 Å, and another for late TMs, generally with a d 10 electronic configuration, where H 2…

The theoretically disclosed, and experimentally confirmed, energy inversion of the lowest singlet ( S 1 ) and triplet ( T 1 ) excited states of organic molecules (i.e., Hund’s rule violation) is investigated herein with the aid of modern and nonempirically derived double-hybrid (DH) density functionals, in the search of the best trade-off between accuracy and computational cost of viable electronic structure methods. For that purpose, we have selected a family of parameter-free expressions differing in their specific formulation (DFT-0DH, DFT-QIDH, DFT0-2, SOS1-DFT-0DH, SOS1-DFT-QIDH, SOS1-DFT0-2, RSX-DFT-0DH, RSX-DFT-QIDH, SOS1-RSX-DFT-0DH, and SOS1-RSX-DFT-QIDH) as well as in the underlying exchange–correlation functional used (PBE vs r 2 SCAN). For the sake of evaluating which DH can correctly describe the singlet–triplet excited-state energy inversion, second-order approximate with singles and doubles method with a spin-component scaling (SCS-CC2) and equation-of-motion coupled cluster singles and doubles (EOM-CCSD) calculations are also carried out. The results highlight the…

Organic light-emitting diodes (OLEDs) capable of radiating narrow-spectrum near-ultraviolet (NUV) light have a wide range of potential applications beyond traditional display purposes. Nevertheless, it remains difficult to achieve both a strong NUV emission and narrow emission spectrum simultaneously. Herein, we report two folded NUV emitters (tCz-BO-BCz and tCz-BO-PCz) featuring through-space charge transfer (TSCT), which consist of tert -butyl carbazole (tCz) as a bridging group, 5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene (BO) as an acceptor, and 9-phenyl-carbazole (BCz) and 9-(pyridin-2-yl)-9 H -carbazole (PCz) as donors. They are fully characterized by crystallography, thermal measurement, cyclic voltammetry, steady-state and transient spectroscopy, and theoretical calculation. They show efficient NUV emissions with narrow full widths at half-maximum (fwhm) of 52 and 44 nm and good photoluminescence quantum yields of 79 and 64% in doped films, respectively. Using tCz-BO-BCz and tCz-BO-PCz as emitters, efficient OLEDs are fabricated, providing narrow NUV light with…

High Resolution Image Download MS PowerPoint Slide The dissolution of porous spherulitic, vaterite particles in aqueous solution is investigated via microscopic monitoring of their size as a function of time. The latter is shown to provide a clear, generic distinction between dissolution controlled either by the rate of a surface-controlled reaction or via dissolution under conditions where the concentration of calcium and carbonate ions is pinned locally by the solubility product of vaterite followed by diffusion away from the dissolving interface into the bulk solution. Dissolution under “thermodynamic control” is shown to be the case for vaterite particles, allowing a value of the solubility product to be determined in the light of the known solution phase equilibria, including the ion pairs CaCO 3, CaOH +, and CaHCO 3 + .

Efficiently converting carbon dioxide (CO 2 ) into valuable fuels or chemicals represents one of the great challenges at the core of current scientific research. Here, we report a DFT-based theoretical study of the reactivity of two main MoS 2 edges for electrocatalytic, or eventually photocatalytic, reduction of CO 2 . By explicitly accounting for the electrode potential via a grand-canonical ensemble that controls the number of electrons, we show that the two edges exhibit different H coverage, which, in turn, directly influences the CO 2 -reduction energy profile under relevant reducing potentials. Specifically, on the S-edge, 0.375 ML H coverage enables CO 2 activation through its adsorption in a bidentate mode with a limiting potential of 0.07 V vs SHE. By contrast, H coverage on the Mo-edge at reducing potentials relevant for CO 2 reduction was determined to be 0 ML. On this bare Mo-edge, CO 2 activation occurs at an additional energy cost of 0.44 eV for −0.80 V. Consequently, the activated CO 2 on the S-edge exhibits comparable and thermodynamically favorable reactivity for…

The experimental knowledge of the AlSb monolayer with a double-layer honeycomb structure is largely based on a recent publication [Le Qin et al., ACS Nano 2021, 15, 8184]. In the present work, we aim to explore the effect of phosphorus alloying on the structural, electronic, and optical properties of the AlSb monolayer (AlSb x P 1– x ). Phonon dispersion curves and cohesive energies, along with the Born criterion, demonstrate the stability of these structures. Our results show that with increasing P-concentration (from 0.375 to 1.0), the bandgaps increase to 1.25 eV, PBE (1.15 eV, PBE + SOC) for the alloyed AlSb structure with 0.875 P content, and an increase of 0.95 eV (PBE) and 0.56 eV (PBE + SOC) compared to that of the pristine AlSb bandgap. The largest bandgap is calculated to be 1.7 eV, PBE (1.65, PBE + SOC) for the AlP monolayer. Interestingly, for all P-concentrations, the bandgaps are direct, signifying potential applications of the material in photovoltaic applications. For P-contents from P = 0 to 0.375, the bandgap initially slightly decreases. The adsorption spectra are…

Janus MXenes, a new category of two-dimensional (2D) materials, show promising potential for advances in optoelectronics, spintronics, and nanoelectronics. Our theoretical investigations not only provide interesting insights but also highlight the promise of Janus MCrCT 2 (M = Ti, Mo; T = O, F, OH) MXenes for future spintronic applications and highlight the need for their synthesis. Electronic structure analysis shows different metallic and semimetallic properties: MoCrCF 2 exhibits metallic property, TiCrC(OH) 2 and MoCrCO 2 exhibit near semimetallicity with spin polarization values of 61 and 86%, respectively, while TiCrCO 2 and TiCrCF 2 are completely half-metallic with 100% spin polarization at the Fermi level. All studied Janus MXenes exhibit intrinsic ferromagnetism, which is mainly attributed to the chromium (Cr) atoms, as shown by the spin density difference plots. Among them, the TiCrCO 2 monolayer stands out with the highest exchange constant and ferromagnetic transition temperature ( T c ). Notably, the O-terminated Janus MXenes exhibit weak perpendicular magnetic…

Proton exchange membrane water electrolysis is a promising technology merging the usage of intermittent renewable energy sources with the production of green hydrogen. Anodic oxygen evolution reaction remains the bottleneck of the efficiency of these devices due to sluggish reaction kinetics, high cost, and scarcity of state-of-the-art catalytic materials. Though most research is focused on the discovery of new catalytic materials, understanding the effects of acid electrolyte anions is crucial to designing and optimizing existing electrocatalysts under diverse electrochemical microenvironments. Herein, we systematically study the effects of acid electrolytes on IrO2(110) surface under OER reaction conditions using density functional theory. The potential dependent anion adsorption results show that HPO4(2-) adsorbs strongest followed by SO4(2-), NO3(1-) and ClO4(1-) respectively at 1.6 V (vs. RHE). HPO4(2-) and SO4(2-) block the Ir-active sites by competitively adsorbing with the OER intermediates while ClO4(1-) does not interfere with OER performance. By evaluating dipole-field…

Starting from 20 amine-functionalized metal–organic framework (MOF) candidates, we have downselected a few for CO 2 adsorption applications. We developed ReaxFF force fields for these MOFs and applied both Grand canonical Monte Carlo calculation and metadynamics simulations to measure CO 2 adsorption both physically and chemically. On one hand, the CO 2 uptake at high CO 2 concentration is found mostly contributed by physisorption. On the other hand, chemisorption is dominant at low CO 2 concentration (e.g., air with 2500 ppm of CO 2 ). The metadynamics simulation results have shown that the energy barrier for CO 2 chemisorption is high for these MOFs and can be significantly reduced with assistance of water or –NH 2 . We found that a mixture of ZIF-8 with polyethylenimine shows a much higher initial CO 2 chemisorption, yet its adsorption capability degrades after repeated uses. In contrast, the utilization rates of amine for the amine-functionalized MOFs are low in adsorption experiments using humid air. While CO 2 chemisorption remains a challenging topic for theoretical study,…

The stability studies, using a rotating disk electrode under a constant current, are commonly used for the development of the oxygen evolution reaction (OER) electrocatalyst, where rise in potential with time is reported to be due to the electrocatalyst degradation. Here, we present a careful examination on the use of this technique on commercial IrO 2 electrocatalysts in acidic media for a duration of 9 h. We observed that a sudden rise in the electrode potential after ∼6 h is rather due to the glassy carbon surface-edge corrosion and detachment between carbon–catalyst interfaces. Indeed, the layer detachment generates an insulating gap between the electrode and carbon layer, resulting in an increase in the cell potential. On this regard, we examine and recommend a potentiodynamic stability test as a reliable and practical method for fast material screening and for the development of OER electrocatalysts.

Engineering nonstoichiometric metal ions in the binary metal oxides is gaining importance in electrochemical energy storage and conversion devices. Zinc cobaltite (ZnCo 2 O 4 ), a p -type spinel structure, has been stringently applied in these fields. In this work, the chemometric ratios of metal ions (Zn and Co) are varied, and the impact of this nonstoichiometry on the electronic structure-modified ZnCo 2 O 4 and its effect on the electrochemical properties are studied in detail. The experiment uses the microwave-assisted hydrothermal method to vary the metal precursor to get the desired nonstoichiometry between Zn and Co in the ZnCo 2 O 4 binary metal oxides. A set of four different samples is prepared by varying the Zn–Co precursor stoichiometric concentrations as 0.5–4, 1.0–4, 1.5–4, and 2.0–4, respectively. These four ZCO samples are first confirmed by X-ray diffraction analysis, followed by refining the structures to determine the nonstoichiometries of the elements and supported by X-ray photoelectron spectroscopy. Density functional theory is applied to determine the…

In this study, we investigate LiMOF (oxyfluoride, M = Mn, Fe, Co, and Ni) via density functional theory calculations as potential electrode material candidates for Li-ion batteries. For the first time, we evaluate their structural, electrical, and electrochemical properties with various proven approaches. Moreover, we compare their properties with each other and with the most relatable in-demand Li electrode materials, e.g., LiCoO 2 . The structural stability of these materials is remarkable due to their 3D solid framework. We find that LiCoOF represents the highest electrical rate capability and conductivity as well as appropriate cell voltage among considered LiMOF materials. After that, LiFeOF demonstrates the appropriate properties; nonetheless, its high voltage may be its limitation. We also debate the pros and cons of other considered materials, i.e., LiNiOF and LiMnOF, which are also promising electrodes. This paper, using novel approaches for more accurate approximations, evaluates these novel materials’ properties as promising electrodes, paving the way for future studies.

The increasingly limited availability of fresh water has become one of the most prominent challenges of our time, and therefore, producing clean water from unconventional sources is of urgent importance. Water harvesting, a process that utilizes changes in the pressure and temperature to capture atmospheric water, has recently drawn considerable attention. In this study, by employing state-of-the-art Monte Carlo simulations, a large-scale study of ∼12,000 metal–organic frameworks (MOFs) included in the Computational-Ready Experimental (CoRE) MOF database is conducted for their potential in water harvesting. The outcomes herein identify hundreds of promising adsorbents that can deliver a greater amount of fresh water per adsorption–desorption cycle than current state-of-the-art adsorbents. Analyses on such large amounts of computational data have also shed light on the structure–property relationships. Overall, the results obtained herein offer significant insights into the future development of MOFs as water adsorbents to harvest atmospheric water.

High Resolution Image Download MS PowerPoint Slide We present BEAST DB, an open-source database comprised of ab initio electrochemical data computed using grand-canonical density functional theory in implicit solvent at consistent calculation parameters. The database contains over 20,000 surface calculations and covers a broad set of heterogeneous catalyst materials and electrochemical reactions. Calculations were performed at self-consistent fixed potential as well as constant charge to facilitate comparisons to the computational hydrogen electrode. This article presents common use cases of the database to rationalize trends in catalyst activity, screen catalyst material spaces, understand elementary mechanistic steps, analyze the electronic structure, and train machine learning models to predict higher fidelity properties. Users can interact graphically with the database by querying for individual calculations to gain a granular understanding of reaction steps or by querying for an entire reaction pathway on a given material using an interactive reaction pathway tool. BEAST DB…

Modulation excitation spectroscopy (MES) with so-called phase-sensitive detection (PSD) is receiving increasing attention for the identification of active species and the elucidation of reaction mechanisms in heterogeneous catalysis. We report the combination of Raman- and UV–vis-MES to be a powerful approach to gain new mechanistic insight into oxide-supported metal catalysts, as illustrated for the CO oxidation over low-loaded Cu/CeO 2 catalysts. Due to the enhanced sensitivity of the MES/PSD approach, Raman spectroscopy provides direct evidence for the active participation of surface lattice oxygen of the ceria support in the reaction mechanism. While Raman-MES enables exclusive insight into the role of the ceria support, UV–vis-MES is shown to be sensitive to the low copper loading. ME-UV–vis spectra highlight the redox activity of copper species and the electronic interactions between copper and ceria, revealing major reduction of Cu 2+ to Cu + while reduction of Ce 4+ to Ce 3+ is minor under the studied reaction conditions. Based on the mechanistic findings provided by the…

High Resolution Image Download MS PowerPoint Slide This study explored the potential of steam-treated bamboo-derived activated carbon (AC) for electric double-layer capacitor (EDLC) applications, using KOH, K 2 CO 3, and Na 2 CO 3 as activation agents to improve electrode materials. The activation process significantly affected the textural properties: KOH enhanced the surface area and micropore volume, K 2 CO 3 impacted micropores and macropores, and Na 2 CO 3 contributed to mesopores and macropores. TEM and SEM images showed distinct morphologies, with K 2 CO 3 exhibiting bubble-like structures and Na 2 CO 3 displaying a foam-like appearance. X-ray photoelectron spectroscopy analysis revealed specific surface modifications of ACs. Electrochemical performance assessments, including charge–discharge behavior, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS), demonstrated the superiority of KOH-AC in EDLC applications due to its high specific area and microporosity. The discharge capacitance of EDLC made from KOH-AC reached 24 F g –1 at a current density of 100 mA…

Recently, vanadium oxides and other semiconductor materials have been intensively studied to use them as nonplasmonic substrates for surface-enhanced Raman scattering (SERS) spectroscopy due to their advantages such as greater uniformity, stability, and spectral reproducibility compared to plasmonic ones. The combination of vanadium pentoxide nanoparticles (V 2 O 5 NPs) with nanostructures of noble metals has shown considerable promise for enhancing the SERS signal, while maintaining the aforementioned advantages. We prepared V 2 O 5 /Au NP films by a novel, simple, fully solvent- and linker-free method: the gas-phase synthesis of vanadium NPs followed by their thermal annealing at 550 °C to obtain V 2 O 5 NP films, which were subsequently decorated with Au nanoislands. Using methylene blue (MB) solution as a test analyte, we observed a significant enhancement of the SERS signal (up to 65 times) from the V 2 O 5 /Au composite compared to those from pure V 2 O 5 substrates. The SERS enhancement in this case arises from the synergy of electromagnetic and chemical (charge-transfer)…

High Resolution Image Download MS PowerPoint Slide The interfacial thermal conductance at a solid/liquid interface ( G ) exhibits an exponential-to-linear crossover with increasing solid/liquid interaction strength, previously attributed to the relative strength of solid/liquid to liquid/liquid interactions. Instead, using a simple Lennard-Jones setup, our molecular simulations reveal that this crossover occurs due to the onset of solidification in the interfacial liquid at high solid/liquid interaction strengths. This solidification subsequently influences interfacial energy transport, leading to the crossover in G . We use the overlap between the spectrally decomposed heat fluxes of the interfacial solid and liquid to pinpoint when “solid-like energy transport” within the interfacial liquid emerges. We also propose a novel decomposition of G into (i) the conductance right at the solid/liquid interface and (ii) the conductance of the nanoscale interfacial liquid region. We demonstrate that the rise of solid-like energy transport within the interfacial liquid influences the relative…

High Resolution Image Download MS PowerPoint Slide Herein, we describe a novel strategy developed for aggregation-induced emission (AIE)/aggregation-caused quenching (ACQ) based on the subtle balance of mild electron-donating/-accepting substituents. The new approach eliminates the need to use bulky and flexible groups that are usually responsible for AIE and ACQ. The obtained regioisomers exhibit the same crystal packing but extremely different behavior upon aggregation, leading to the extremely bright aggregates of the compounds being dark in solution and vice versa. Such an approach opens a way to explore a new method of controlling small molecules’ AIE/ACQ behavior.

High Resolution Image Download MS PowerPoint Slide All-inorganic halide perovskites have received a great deal of attention as attractive alternatives to overcome the stability issues of hybrid halide perovskites that are commonly associated with organic cations. To find a compromise between the optoelectronic properties of CsPbI 3 and CsPbBr 3, perovskites with CsPb(Br x I 1– x ) 3 mixed compositions are commonly used. An additional benefit is that without sacrificing the optoelectronic properties for applications such as solar cells or light-emitting diodes, small amounts of Br in CsPbI 3 can prevent the inorganic perovskite from degrading to a photo-inactive non-perovskite yellow phase. Despite indications that strain in the perovskite lattice plays a role in the stabilization of the material, a full understanding of such strain is lacking. Here, we develop a reactive force field (ReaxFF) for perovskites starting from our previous work for CsPbI 3, and we extend this force field to CsPbBr 3 and mixed CsPb(Br x I 1– x ) 3 compounds. This force field is used in large-scale…

Herein, we have fabricated two different types of amorphous carbon-rich g-C 3 N 4 systems with improved heteroatom functionalities and desired porosities from highly defined amorphous carbon dots and melamine. It improves the visible light absorption and effective active sites for photocatalysis compared to the pristine g-C 3 N 4 matrix. Details of structural and elemental properties have been investigated by transmission electron microscopy, X-ray photoelectron spectroscopy, and N 2 adsorption–desorption isotherms. This was further supported by the intricate photophysical properties of the materials. Notably, the photoinduced charge separation drastically increases with increasing the amorphous C and pyrrolic N content in the g-C 3 N 4 matrix. Photocatalytic solar H 2 production also follows the same trend. The calculated external quantum efficiency for solar H 2 production has reached almost 30% for the optimized material, which is one of the highest H 2 production efficiencies reported to date compared to similar all-carbon-based nanomaterials. Depending on the structural…