The 100 most-cited articles in The Journal of Physical Chemistry C, 2023

An in-depth understanding of battery degradation and aging in- Operando not only plays a vital role in the design of battery managing systems but also helps to ensure safe use and manufacturing optimization of lithium-ion batteries (LIBs) in large-scale applications. Electrochemical impedance spectroscopy (EIS) is a nondestructive method which unravels electrode kinetic processes inside the batteries in different time domains, including charge-transfer reactions, interfacial evolutions, and mass diffusions. It has become a powerful diagnosis and pre/prognosis tool in battery aging research, as it provides important insight into the changes of internal electrochemical processes by correlating the impedance evolution to degradation mechanisms. This review gives a critical overview on rapidly developing impedance techniques for degradation and aging investigation of Li-ion batteries. The EIS variations of LIBs at different aging conditions of calendar aging and accelerated aging are systematically summarized. In addition, the working principles, data validation, and modeling methods,…

Two-dimensional (2D) transition metal carbides and nitrides are among the newest, and probably largest, families of 2D materials that have been discovered. They have shown promise in many applications, such as electromagnetic shielding, energy storage devices like batteries and supercapacitors, transparent conductive electrodes, as catalysts for hydrogen production, and several others. Their general formula is M n +1 X n T z ( n = 1–4) or M 1.33 XT z, where M is an early transition metal, X is carbon and/or nitrogen, and T z represents various terminations present upon etching the Al layer. The first MXene discovered, Ti 3 C 2 T z, was synthesized by etching aluminum (Al) from the nanolaminated MAX phase Ti 3 AlC 2 using hydrofluoric acid (HF). Since the discovery of Ti 3 C 2 T z in 2011, more than 30 other MXene chemistries have been reported with different M and X elements. It has been observed that, as expected, changing the MXene chemistry also influences the properties in the range of applications listed above, allowing us to tailor them according to what suits the application…

Hydrogen-derived power is one of the most promising components of a fossil fuel-independent future when deployed with green and renewable primary energy sources. Energy from the sun, wind, waves/tidal, and other emissions-free sources can power water electrolyzers (WEs), devices that can produce green hydrogen without carbon emissions. According to recent International Renewable Energy Agency reports, most WEs employed in the industry are currently alkaline water electrolyzers and proton-exchange membrane water electrolyzers (PEMWEs), with ∼200 and ∼70 years of commercialization history, respectively. The former suffers from inherently limited current densities due to inevitable gas crossover, operates using corrosive (7 M) alkaline solutions, and requires large installation footprints, while the latter requires expensive and scarce precious metal-based electrocatalysts. An emerging technology, the anion-exchange membrane water electrolyzer (AEMWE), seeks to combine the benefits of both into one device while overcoming the limitations of each. AEMWEs afford higher operating current…

Photocatalysis induced by localized surface plasmon resonance of metallic nanoparticles has been studied for more than a decade, but photocatalysis originating from direct interband excitations is still under-explored. The spectral overlap and the coupling of these two optical regimes also complicate the determination of hot carriers' energy states and eventually hinder the accurate assignment of their catalytic role in studied reactions. In this Featured Article, after reviewing previous studies, we suggest classifying the photoexcitation via intra- and interband transitions where the physical states of hot carriers are well-defined. Intraband transitions are featured by creating hot electrons above the Fermi level and suitable for reductive catalytic pathways, whereas interband transitions are featured by generating hot d-band holes below the Fermi level and better for oxidative catalytic pathways. Since the contribution of intra- and interband transitions are different in the spectral regions of localized surface plasmon resonance and direct interband excitations, the wavelength…

High Resolution Image Download MS PowerPoint Slide Heteroatom doping is regarded as a promising method for controlling the optoelectronic properties of carbon nanodots (CNDs), notably their fluorescence and antioxidation activities. In this study, phosphorous (P) and boron (B) are doped at different quantities in the CNDs’ structures to investigate their effects on the optical and antioxidation properties. Both the dopants can enhance light absorption and fluorescence, yet via different approaches. After doping, the UV–vis absorption of high P%-CNDs demonstrated a slight blue shift (348–345 nm), while the high B%-CNDs showed a minor red shift (348–351 nm), respectively. The fluorescence emission wavelength of doped CNDs changes marginally while the intensity increases significantly. Structural and composition characterizations show elevated levels of C═O on the surface of high P%-CND compared to low P%-CNDs. In B-doped CNDs, more NO 3 – functional groups and O–C═O bonds and fewer C–C bonds form at the surface of high B%-CNDs compared to the low B%-CNDs. A radical scavenging study…

A series of CdS quantum dots (QDs) at low temperature were grown on the nanosheets (NSs) of g-C 3 N 4 through an in situ successive ionic layer adsorption and reaction process. The visible light active band gap of ultrathin g-C 3 N 4 NSs has attracted more attention due to its essential bandgap for the water splitting reaction. However, a single catalyst with a limited number of active sites does not exhibit significant photo/electrocatalytic activity for hydrogen production. In current strategies, the development of a photogenerated charge transfer-driven type-II CdS QDs/g-C 3 N 4 heterostructure demonstrates an enhanced hydrogen evolution reaction with an amount of 14.8 mmol g cat –1 of H 2 gas and an AQY of 27.6% as a result of a decreased charge transfer resistance and a significantly increased electrochemical surface area. Additionally, the as-prepared catalyst has shown overpotentials of 182 and 382 mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) reactions to reach the current density at 10 mA cm –2, respectively. In addition, the bifunctional…

A lateral phototransistor structure based on mechanically exfoliated multilayer black arsenic (b-As) is produced to test its in-plane anisotropy of photoelectrical properties. First, the morphology and structure of the b-As flake are investigated with respect to light polarization and crystal structure orientation. Then, the Raman modes, demonstrating a strong anisotropic nature of twofold symmetry for in-plane vibrations and fourfold symmetry for out-of-plane vibrations, allow us to define the armchair and zigzag crystal directions. The lateral photodetector structure has been prepared by depositing polar-oriented electrodes with an angular step of 45° correlated along the b-As crystal directions. Angle-resolved electrical transport and polarization-resolved photocurrent measurements show its strong in-plane anisotropic photoelectrical properties when conductance and photocurrent are about 2 times higher across the armchair direction than the zigzag one. The respective photoresponsivity at 980 nm is 0.44 and 0.19 A/W with the dichroic ratio of 2.3. The intrinsic linear dichroism…

Revealing the structure–optical property relationship of aggregation-induced emission (AIE) species (AIEgens) and achieving the synergy between AIE and antenna effect are challenging. Herein, we study the emission behaviors of three AIE ligands with tetraphenyl structures, 1,2,4,5-tetrakis(4-carboxyphenyl)benzene ( L1 ), 2,3,5,6-tetrakis(4-carboxyphenyl)pyrazine ( L2 ), and 1,1,2,2-tetrakis(4-carboxyphenyl)ethylene ( L3 ), and find their ladder-shaped emission wavelength. In combination with terephthalic acid ( L0 ), we construct a staff gauge from L0 to L3 to realize different sensitization for Ln 3+ from the sensitization of both Eu 3+ and Tb 3+ to single Eu 3+ and then to non-sensitization. We proposed the threshold value of 5000 cm –1 for complete sensitization from the different optical behaviors and energy levels of the lanthanide metal–organic frameworks (Ln-MOFs). Coplanar degree of L1–L3 is proposed to explain their optical behaviors and different sensitization. Thus, we revealed the connection among the energy levels, emission wavelength, and their effect on antenna effect…

Nuclear energy is considered a suitable and eco-friendly alternative for combating the rising greenhouse gases in the atmosphere from excessive fossil fuel consumption. Betavoltaic battery is a form of nuclear technology that utilizes the decay energy of β-emitting radioisotopes to produce electrical power. Owing to its long shelf life, high specific energy density, and ability to work under extreme conditions, it has been a subject of considerable research attention in the past few years. Despite significant research on betavoltaic battery, several impediments to realizing high energy conversion efficiency and maximum power density have yet to be overcome. This Review Article comprehensively discusses the challenges and recent research progress of betavoltaic battery development. First, promising strategies for improving betavoltaic battery performance, theoretical principles, and equations for quantifying betavoltaic battery efficiency are discussed. Then a thorough overview of several β-radiation absorbing materials, such as traditional semiconductors, metal oxides, and…

Cu/Cu 2 O/CuO nanocomposites were synthesized using the simple wet chemical approach for the production of dihydrogen as a potential fuel source and for the detoxification of dyes. The formation of Cu/Cu 2 O/CuO nanocomposites is confirmed by powder X-ray diffraction, whereas the W-H plot revealed the average particle size of nanocomposite approximately 17 nm, which is in good agreement with the Scherrer method and transmission electron microscopy analysis. The uniform distribution of Cu and O elements was supported by the elemental mapping of the nanocomposite. Band gaps of CuO and Cu 2 O were found to be 1.71 and 1.92 eV, respectively, using diffuse reflectance spectroscopy spectra and Kubelka–Munk functions. The oxygen vacancies in the nanocomposite are confirmed by various analytical spectroscopic techniques, such as electron paramagnetic resonance, Raman, photoluminescence, and X-ray photoelectron spectroscopy (XPS) spectra. The significant boost in the performance of the fabricated nanocomposite was observed and is attributed to the formation of a heterojunction and existence…

Due to the low sulfur utilization, slow battery kinetics, and shuttle effect of lithium polysulfides, the practical application of lithium-sulfur (Li-S) batteries is severely limited. Understanding the reaction mechanism is very important for the design and application of high-performance batteries. Herein, the adsorption mechanism of LiPSs, the reaction mechanism of a battery electrode, and the catalytic decomposition of LiPSs on pristine, single-atom, and dual-atom doping C9N4 (C9N4, M/C9N4, and M1-M2/C9N4) nanosheet are comprehensively considered for the first time. Through bond length analysis, charge analysis and energy analysis, the doping of metal atoms, especially co-doping of V and Zn atoms (Zn-V/C9N4), can greatly improve the adsorption performance of material C9N4. More importantly, Zn-V/C9N4 can significantly reduce the reaction rate-limiting step energy barrier of the battery electrode (0.144 eV) and the decomposition energy barrier of Li2S (0.661 eV). The simulation results show that high catalytic activity depends on the unique d-orbital coupling and the "pull" effect…

The emission of carbon dioxide (CO 2 ) induced by the widespread use of fossil fuels has caused global warming and climate issues. Photocatalytic CO 2 reduction technology, which utilizes solar energy to convert CO 2 into carbon-based fuels, provides a promising sustainable green way to ameliorate the energy crisis and reduce CO 2 concentration in the atmosphere. Multicarbon products (C2+) with higher energy density and larger market value attract widespread research interests. This review is focused on the recent progress of photocatalytic reduction of CO 2 to C2+ products. Starting from the discussion on the fundamental mechanism of photocatalytic CO 2 conversion to C2+ products, the strategies of photocatalyst design for C2+ fuels synthesis from CO 2 are summarized. Particularly, the photocatalyst optimization approaches for improving the activity and especially selectivity of CO 2 reduction reaction (CRR) to access C2+ products are highlighted. Finally, some personal outlook on this research direction of photocatalytic CRR to C2+ products is presented. This review is expected to…

Solution-processed photodetectors such as those based on halide perovskite semiconductors show attractive properties for emerging applications in lightweight, transparent, flexible, and spectrally selective optical sensors. The transient photocurrent to a light perturbation often shows a complex response characterized by sharp transient peaks in the photocurrent curves when the stimulus changes or slow rise times depending on features such as the applied voltage or the active layer thickness. We present the characteristic response of halide perovskite photodetectors by measuring the response of a FTO/PEDOT/MAPbBr 3 /Au device, and we establish a new model for the analysis of the dominant transient shapes. The model uses very basic suppositions of photoconversion to electricity: charge generation, collection, and polarization. These standard properties are combined with a new essential feature: a delayed photocurrent mode that forms a photoinduced chemical inductor. This last property is caused by ionic–electronic interaction phenomena related to the well-known inverted hysteresis of…

High Resolution Image Download MS PowerPoint Slide The atomic scale dynamics of halide perovskites have a direct impact not only on their thermal stability but also on their optoelectronic properties. Progress in machine-learned potentials has only recently enabled modeling the finite temperature behavior of these materials using fully atomistic methods with near first-principles accuracy. Here, we systematically analyze the impact of heating and cooling rate, simulation size, model uncertainty, and the role of the underlying exchange-correlation functional on the phase behavior of CsPbX 3 with X = Cl, Br, and I, including both the perovskite and the δ-phases. We show that rates below approximately 60 K/ns and system sizes of at least a few tens of thousands of atoms should be used to achieve convergence with regard to these parameters. By controlling these factors and constructing models that are specific for different exchange-correlation functionals, we then assess the behavior of seven widely used semilocal functionals (LDA, vdW-DF-cx, SCAN, SCAN+rVV10, PBEsol, PBE, and PBE+D3).…

Graphene’s success has led to the theoretical prediction and experimental synthesis of various 2D carbon-based allotropes. To explore the mechanical, structural, electronic, and optical properties of 8-16-4 graphyne, we employed density functional theory using the GGA/PBE approach, ab initio molecular dynamics (AIMD), and classical reactive molecular dynamics simulations. Our AIMD results indicate that this material demonstrates excellent dynamical and thermal stabilities. It has a formation energy of −8.57 eV/atom and an elastic moduli of 262.37 GPa. Regarding its band structure, this graphyne analogue is a semimetal with two Dirac cones. It also exhibits transparency and intense optical activity in the infrared region. Notably, the band structure of 8-16-4 graphyne remains practically unchanged at moderate strain regimes. To our knowledge, this is the first known 2D carbon allotrope to exhibit such behavior.

The hot electrons in carbon-based materials exhibit interesting ballistic transport behaviors for designing high-performance single-electron transistors. However, the cooling of such hot electrons back to the equilibrium state may be slowed down by the excessively populated optical phonons, thus limiting their ballistic transport. Therefore, a thorough understanding of the coupling between hot electrons and optical phonons is of critical importance. Here, by varying the thickness of a multilayer graphene film on a supporting substrate, we investigated the competition pathways of the energy relaxation of the photoinduced hot electrons through coupling with the optical, surface, and acoustic phonons. The difference in the τ 2 values indicates that thickness plays an important role in the optical phonon population. For the multilayer graphene film thickness less than 3 nm, the super-collision model describes the hot electron cooling dynamics that is strongly affected by the surface phonons from the supporting substrate. As the multilayer graphene film thickness increases from 3 to 20…

NiO-based electrocatalysts, known for their high activity, stability, and low cost in alkaline media, are recognized as promising candidates for the oxygen evolution reaction (OER). In parallel, atomic layer deposition (ALD) is actively researched for its ability to provide precise control over the synthesis of ultrathin electrocatalytic films, including film thickness, conformality, and chemical composition. This study examines how NiO bulk and surface properties affect the electrocatalytic performance for the OER while focusing on the prolonged electrochemical activation process. Two ALD methods, namely, plasma-assisted and thermal ALD, are employed as tools to deposit NiO films. Cyclic voltammetry analysis of ∼10 nm films in 1.0 M KOH solution reveals a multistep electrochemical activation process accompanied by phase transformation and delamination of activated nanostructures. The plasma-assisted ALD NiO film exhibits three times higher current density at 1.8 V vs RHE than its thermal ALD counterpart due to enhanced β-NiOOH formation during activation, thereby improving the OER…

We apply the machine learning (ML) tool to calculate the Gibbs free energy (Δ G ) of reaction intermediates rapidly and accurately as a guide for designing porphyrin- and graphene-supported single-atom catalysts (SACs) toward electrochemical reactions. Based on the 2105 DFT calculation data from the literature, we trained a support vector machine (SVR) algorithm. The hyperparameters were optimized using Bayesian optimization along with 10-fold cross-validation to avoid overfitting. Based on the Shapley Additive exPlanation (SHAP) and permutation methods, the feature importance analysis suggests that the most important parameters are the number of pyridinic nitrogen (Npy), the number of d electrons (θ d ), and the number of valence electrons of reaction intermediates. Inspired by this feature importance analysis and the Pearson correlation coefficient, we found a linear dependent, simple, and general descriptor (φ) to describe Δ G of reaction intermediates ( e.g ., Δ G OH* = 0.020φ – 2.190). Using the trained SVR algorithm, Δ G OH*, Δ G O*, Δ G OOH*, Δ G OO*, Δ G H*, Δ G COOH*, Δ G…

High Resolution Image Download MS PowerPoint Slide A strategy that can be used to develop metal–organic frameworks (MOFs) to capture per- and poly-fluoroalkyl substances (PFAS) from water is functionalizing them with fluorine moieties. We investigated different fluorine-functionalization strategies and their performance in removing PFAS from water using molecular simulations. Perfluorooctanoic acid (PFOA), one of the most widely encountered PFAS in water sources, was used as the probe molecule. Our simulations show that fluorine functionalization by incorporating fluorinated anions as bridging ligands in MOFs creates additional binding sites for PFOA; however, the same sites also attract water molecules, which casts doubt on their potential use. In contrast, trifluoromethyl or fluorine substitution of the MOF ligands results in higher hydrophobicity. However, the pores fluorinated with this method should have the optimum size to accommodate PFOA. Likewise, post-synthetic fluorine functionalization of MOFs through grafting of perfluorinated alkanes showed increased PFOA affinity.…

Deciphering the calcium silicate hydrate (C-S-H) surface is crucial for unraveling the mechanisms of cement hydration and property development. Experimental observations of C-S-H in cement systems suggest a surface termination which is fundamentally different from the silicate-terminated surface assumed in many atomistic level studies. Here, a new multiparameter approach to describing the (001) basal C-S-H surface is developed, which considers how the surface termination affects the overall properties (Ca/Si ratio, mean chain length, relative concentration of silanol and hydroxide groups). Contrary to current beliefs, it is concluded that the (001) C-S-H surface is dominantly calcium terminated. Finally, an adsorption mechanism for calcium and hydroxide ions is proposed, which is in agreement with the surface charge densities observed in previous studies.

Electrochemical nitrate reduction reaction (NO 3 RR) has promise for both nitrogen pollution management and low-temperature ammonia production instead of the conventional Haber–Bosch process. Nevertheless, it relies on electrocatalysts with controllable reaction pathways and product selectivity. Herein, we design novel homonuclear double-atom catalysts (DACs) supported on N-doped graphene (TM 2 /N 6 -G) as potential NO 3 RR catalysts using first-principles calculations. The results reveal that Cr 2 /N 6 -G, Mn 2 /N 6 -G, and Cu 2 /N 6 -G serve as the most promising NO 3 RR catalysts, as they exhibit stability, excellent activity, high selectivity (faradic efficiency of >61.28%), and low limiting potentials (−0.46, −0.45, and −0.36 V for Cr 2 /N 6 -G, Mn 2 /N 6 -G, and Cu 2 /N 6 -G, respectively). In addition, multiple-level descriptors and volcano plots provide insight into the origin of NO 3 RR activity and enable fast prescreening among numerous candidates. Furthermore, considerable potential energy barriers are found in the formation of byproducts NO 2, NO, and N 2 O, validating…

As the most advanced energy storage devices, lithium ion batteries (LIBs) have captured a great deal of attention and have been developed swiftly during the past decades. However, the improved fast-charging performance is more urgent than ever for time-saving and convenience, which is generally limited by the graphite anode. Recent studies have revealed that the fast-charging performance of graphite anodes is highly dictated by the properties of the electrolyte. Therefore, the investigations on fast-charging graphite based on designs of electrolytes are summarized from two aspects: solid electrolyte interphase (SEI) structures and solvated lithium ion structures. Finally, challenges and prospects for further research toward fast-charging graphite anodes are proposed.

Electrochemical CO 2 reduction reaction (CO 2 RR) is an important process which is a potential way to recycle excessive CO 2 in the atmosphere. Although the electrocatalyst is the key toward efficient CO 2 RR, the progress of discovering effective catalysts is lagging with current methods. Because of the cost and time efficiency of the modern machine learning (ML) algorithm, an increasing number of researchers have applied ML to accelerate the screening of suitable catalysts and to deepen our understanding in the mechanism. Hence, we reviewed recent applications of ML in the research of CO 2 RR by the types of electrocatalyst. An introduction on the general methodology and a discussion on the pros and cons for such applications are included.

Forces between hydrophilic surfaces mediated by water are important in various systems from lipid membranes and solid surfaces to colloids and macromolecules, first discovered as a significant addition to DLVO forces at the nanoscale.These "hydration forces" have been studied in great detail experimentally using osmotic stress measurements, surface force apparatus, and AFM, and they have also been the subject of multiple theories and simulations.One spectacular feature observed in experimental and simulation studies was the nonmonotonic, oscillatory decay in the forces between atomically smooth surfaces.Forces between "rougher" surfaces exhibit only quasi-exponential, monotonic decay.Here we revisit this hydration force problem by exploring the consequences of an extended phenomenological Landau-Ginzburg approach that describes nonlocal correlations in water, linking them with the key features of the wave-number k-dependent nonlocal dielectric function of water.With corresponding boundary conditions, this theory predicts the observed oscillatory decay in hydration force between…

Lattice oxygen redox of solid-state material hosts is an emerging observation in electrochemistry. Toward the anodic oxygen evolution reaction (OER) in water electrolysis with sluggish kinetics, the activation of lattice oxygen alters the reaction mechanism profoundly, either facilitating the nucleophilic attack of O–O coupling in the conventional adsorbate evolution mechanism (AEM) or directly triggering the participation of lattice oxygen into gaseous O 2 generation via the lattice oxygen-mediated mechanism (LOM). In-depth understanding at the molecular level further provides the research community with fundamental guidelines for advanced OER catalyst design. Herein, we present the physicochemical principles of correlation between the band alignment and the preferential OER mechanism. The recent progress about the key roles of lattice oxygen activation in OER activity improvement is then comprehensively discussed. Finally, we propose the remaining challenges and future perspectives of lattice oxygen activation for the potential advancements in electrocatalysis.

High Resolution Image Download MS PowerPoint Slide Hydrogen bonds (HBs) play an important role in the rotational dynamics of organic cations in hybrid organic/inorganic halide perovskites, thus affecting the structural and electronic properties of the perovskites. However, the properties and even the existence of HBs in these perovskites are not well established. In this study, we investigate HBs in perovskites MAPbBr 3 (MA + = CH 3 NH 3 + ), FAPbI 3 (FA + = CH(NH 2 ) 2 + ), and their solid solution with composition (FAPbI 3 ) 7/8 (MAPbBr 3 ) 1/8, using ab initio molecular dynamics and electronic structure calculations. We consider HBs donated by X-H fragments (X = N and C) of the organic cations and accepted by the halides (Y = Br and I) and characterize their properties based on pair distribution functions and on a combined distribution function of the hydrogen–acceptor distance with the donor–hydrogen–acceptor angle. By analyzing these functions, we establish geometrical criteria for HB existence based on the hydrogen–acceptor (H–Y) distance and donor–hydrogen–acceptor angle…

In this work, we present the ChemNLP library that can be used for (1) curating open access datasets for materials and chemistry literature, developing and comparing traditional machine learning, transformers and graph neural network models for (2) classifying and clustering texts, (3) named entity recognition for large-scale text-mining, (4) abstractive summarization for generating titles of articles from abstracts, (5) text generation for suggesting abstracts from titles, (6) integration with density functional theory dataset for identifying potential candidate materials such as superconductors, and (7) web-interface development for text and reference query. We primarily use the publicly available arXiv and PubChem datasets, but the tools can be used for other datasets as well. Moreover, as new models are developed, they can be easily integrated in the library. ChemNLP is available at the websites: https://github.com/usnistgov/chemnlp and https://jarvis.nist.gov/jarvischemnlp/ .

Ultrafast optical microscopy, generally employed by incorporating ultrafast laser pulses into microscopes, can provide spatially resolved mechanistic insight into scientific problems ranging from hot carrier dynamics to biological imaging. This Review discusses the progress in different ultrafast microscopy techniques, with a focus on transient absorption and two-dimensional microscopy. We review the underlying principles of these techniques and discuss their respective advantages and applicability to different scientific questions. We also examine in detail how instrument parameters such as sensitivity, laser power, and temporal and spatial resolution must be addressed. Finally, we comment on future developments and emerging opportunities in the field of ultrafast microscopy.

Deepwater oil and gas development is extremely difficult and challenging. One of the most critical challenges stems from hydrate deposition, aggregation, and the eventual blocking of the deepwater oil and gas transportation system. The low-temperature and high-pressure environment in the deepwater oil and gas field causes the combination of gas molecules and water molecules to form hydrate, thus affects the hydrocarbon transportation. In this Perspective, to discuss the commonly faced safety issues for deepwater oil, gas, and gas hydrate development, the following three critical problems are comprehensively summarized and analyzed. First, the mechanisms of phase transition, aggregation, and blockage of the hydrate in the multiphase transport system have been investigated from the microscopic perspective to macroscopic characteristics. Second, based on different theoretical models, the algorithms are discussed to introduce an online monitoring technique for hydrate blockage, which can detect the safety risks and provide early warnings. Furthermore, for hydrate blockage prevention and…

The Z-scheme heterostructure photocatalysts have irreplaceable advantages over other heterostructures due to their ability to separate the spatial carriers and retain strong redox ability. In this study, we explored the SnS 2 /β-As (β-arsenene) van der Waals heterostructure with Z-scheme properties and suitable band edge positions as a potential photocatalyst for overall water splitting. Under appropriate conditions, the hydrogen evolution reaction (HER) barrier is much closer to 0. Based on the oxidation product criteria, the SnS 2 /β-As heterostructure photocatalyst may generate multiple end products, including • OH, H 2 O 2, and O 2 . Moreover, we screen the optimal and most possible reaction pathway OER-III under irradiation among three underlying oxygen evolution reaction (OER) mechanisms, in which the intermediate species HOOH* acts as a bridge for subsequent reactions. The solar-to-hydrogen conversion efficiency of the heterostructure can reach 17.18%. This work provides new insights into designing superior photocatalysts for overall water splitting and recognizing the OER…

Dynamic structural changes of single-atom catalysts (SACs) are key to many reactions that were reported to be catalyzed by supported single atoms. To understand these changes, systematic in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and X-ray absorption spectroscopy (XAS) experiments were performed under reducing (1% CO) and oxidizing (1% CO + 1% O 2 ) reaction atmospheres at room temperature over CeO 2 -supported late transition metals (Ru, Rh, Pd, Ir, and Pt) synthesized via two different methods (wet impregnation and precipitation) to account for the influence of surface properties. As a general trend, the CO vibrational frequencies downshifted under the CO atmosphere, which we assigned to the formation of clusters. Upon changing the gas mixture to more oxidizing (1% CO + 1% O 2 ), single sites are retained as evidenced by the CO vibrational frequencies at higher wavenumbers. Among the investigated metals, Pt 2+ and Pd 2+ are more prone to cluster formation, and Rh 3+ and Ru 4+ are found to be stable as single sites following the order Rh > Ru > Ir…

High Resolution Image Download MS PowerPoint Slide Tandem organic solar cells can potentially drastically improve the power conversion efficiency over single-junction devices. However, there is limited research on device development and often ca. 1% improvement over single-junction devices. Because of the complex nature of organic material compatibility and properties, such as energy-level alignment and maximizing absorption spectra, and the vastness of chemical space, computational guidance is vital. The first part of this work uses a new data set of 1225 donor/non-fullerene acceptor (NFA) pairs containing 1001 unique pairs, one of the largest to date, to train an ensemble machine learning model to predict device efficiency (RMSE = 1.60 ± 0.14%). Next, a series of genetic algorithms (GAs) are used to discover high-performing NFAs and polymer donors and then combinations of them for potential high-efficiency tandem cells. Interesting design motifs show up in high-performing NFAs, such as diphenylamine substituents on the core and 3D terminal groups. The donor polymers from the GAs…

A composite solid polymer electrolyte (CSPE) is the best candidate in all-solid-state lithium metal batteries because of its flexibility, high safety, wide electrochemical stability, relatively high ionic conductivity, and excellent compatibility with the lithium metal. In this work, the garnet-type Li 6.75 La 3 Zr 1.75 Ta 0.25 O 12 (LLZTO) is introduced into a poly(ethylene oxide) (PEO)/poly(vinylidene fluoride–hexafluoropropylene) (PVDF–HFP)-based CSPE (PEO/PVDF–HFP/LLZTO CSPE). The PEO/PVDF–HFP/LLZTO CSPE possesses a high lithium-ion transference number of 0.47, a high ionic conductivity of 2.65 × 10 –4 S cm –1, a wide electrochemical window of 5.55 V vs Li + /Li, and effective inhibition of lithium dendrite growth for 1000 h with a current density of 0.10 mA cm –2 . Furthermore, the Li//LiFePO 4 cell assembled with the PEO/PVDF–HFP/LLZTO CSPE delivers superior rate capability and good cycling stability. Therefore, the PEO/PVDF–HFP/LLZTO CSPE is a very promising candidate for high-performance all-solid-state lithium metal batteries.

Current Li-ion battery (LIB) electrolytes employ mixed solvents consisting of ethylene carbonate (EC) and linear carbonates (LCs). Notably, the ion conductivities of the EC/LC electrolytes follow the order dimethyl carbonate > ethyl methyl carbonate > diethyl carbonate despite the similar physicochemical properties of the three LCs. However, the origin of this order remains elusive. In this study, we elucidated the important role of conformational isomerism of the LC solvent on salt dissociation in 0.1–3.0 M LiPF 6 EC/LC solutions, using Raman spectroscopy and dielectric relaxation spectroscopies, along with first-principles calculations. The conductivity trend is closely related to the difference in the degree of salt dissociation, which, in turn, is determined by the fraction of the polar cis–trans-LC conformer, as this conformer participates in Li-ion solvation as readily as EC does. This study demonstrates the critical role of the conformational isomerism of the solvents in the electrolyte conductivity, indicating the feasibility of utilizing solvent isomerism to tune the bulk…

Lithium extraction from brine or seawater using membrane technology has attracted extensive attention in recent years. Graphene oxide (GO), as one of the two-dimensional materials, has been proven as a competitive candidate for membranes. However, the GO membranes still suffer challenges for ion sieving due to the swelling in the aqueous solution. In this work, a GO–PEI membrane with positively charged channels was constructed by polyelectrolyte polyethyleneimine (PEI) molecular chain-grafted GO nanosheets. The GO–PEI membrane showed a high selectivity of 22.2 for Li + /Mg 2+, together with a competitive Li + permeation rate of 0.09 mol m –2 h –1 in a binary permeation test. In addition, the membrane showed excellent stability during the separation process. The enhanced Li + /Mg 2+ separation performance of the GO–PEI membrane could be mainly attributed to the synergistic effect of size sieving and electrostatic repulsion. We further systematically studied the influence of various variables, such as PEI molecular weight, PEI content, membrane thickness, and ion concentration, on…

The electrocatalytic hydrogen evolution reaction (HER) is of central importance for water electrolysis and green hydrogen production. Platinum represents the state-of-the-art electrocatalyst for the HER. The HER on the platinum surface displays distinct pH dependent kinetics, showing much more sluggish kinetics in alkaline media than in acidic electrolytes. The fundamental origin of the pH-dependent HER kinetics has attracted substantial interest in the electrocatalysis community. Considerable efforts have been made to understand the distinct HER kinetics in different electrolytes, although with frequent inconsistencies among different studies. A fundamental molecular level understanding of the pH dependent HER kinetics remains elusive but is essential for developing more efficient and cost-effective water electrolysis technologies. This Perspective summarizes the current status of the mechanistic understanding of HER on platinum surface, analyzes several intertwined factors that could alter the fundamental molecular pathways and reaction kinetics in different electrolytes, and…

Since the discovery of the first MXene, Ti 3 C 2 T z, in 2011, more than 30 new MXene chemistries have been reported. A universal method via which all MXenes can be synthesized is by etching the “A” layer from the MAX phase using hydrofluoric acid, HF. After etching, to delaminate the resulting MXene multilayers, MLs, they are typically treated with a surfactant like tetrabutylammonium hydroxide, TBAOH, tetramethylammonium hydroxide, TMAOH, dimethyl sulfoxide, DMSO, etc. In our earlier work, we found that treating HF-etched Ti 3 C 2 T z MLs with a base like NaOH renders them ion-exchangeable, similar to the earlier reported treatments using expensive and more toxic bases like TMAOH or TBAOH. In this work, we study the effects of sodium hydroxide, NaOH, treatment on Nb 2 CT z and Mo 2 Ti 2 C 3 T z MXene MLs. We show that, similar to Ti 3 C 2 T z, Na ions also intercalate in these two MXenes. This was clearly confirmed by X-ray diffraction analysis, which showed an increase in the interlayer spacing post treatment of HF-etched MXenes with NaOH. This increase in the interlayer space…

Molybdenum disulfide (MoS 2 ) possesses distinct electrochemical and electronic properties, as a unique material, and raises a growing amount of interest in both its synthesis and application. Compared with the most stable and widely existing triangle prismatic (2H) phase of MoS 2, 1T-MoS 2, a metallic octahedral but metastable crystal phase, occupies a more important position within the application in electrochemical reactions, photoelectron catalysis, photodetectors, photothermal agents, energy storage devices, and biosensors. In this article, an exploration of the key reasons for the different stabilities of 1T- and 2H-MoS 2 is conducted via density functional theory (DFT) calculations. Meanwhile, simple but facile bonding patterns of valence orbits in 1T- and 2H-MoS 2 are proposed with an emphasis on their properties and stability. Consequently, the electron count and density of state (DOS) unification of MoS 2 are considered as the secrets for the 2H-to-1T phase transition, where the most reported manners for obtaining 1T-MoS 2 can be well explained. The finding here has a…

High Resolution Image Download MS PowerPoint Slide RuO 2 and IrO 2 are among the most active catalysts for the Oxygen Evolution Reaction (OER). Recently, it was demonstrated that the catalytic surface of these oxides plays a role in the reaction, where a hydrogen bond with a neighbor OH group stabilizes an unconventional −OO intermediate (−OO–H), prior to O 2 evolution. Quantum chemical calculations neglecting solvation effects indicated that this intermediate is more stable than the conventional −OOH, and that deprotonation of the stabilizing −OH is the rate limiting step for OER on RuO 2 (110) and RuO 2 (100). In this work, we investigate the role of water molecules on the relative stability of −OOH and −OO–H oxygenates on RuO 2 (110) by means of density functional theory calculations combined with ab initio Molecular Dynamics simulations (AIMD). We show that the two intermediates participate in a hydrogen bonding network with water to a similar extent, but leading to different interfacial water structures, with possible implications on interfacial proton dynamics and reaction…

High Resolution Image Download MS PowerPoint Slide Phonon–phonon and electron/exciton–phonon coupling play a vitally important role in thermal, electronic, as well as optical properties of metal halide perovskites. In this work, we evaluate phonon anharmonicity and coupling between electronic and vibrational excitations in novel double perovskite Cs 2 NaFeCl 6 single crystals. By employing comprehensive Raman measurements combined with first-principles theoretical calculations, we identify four Raman-active vibrational modes. Polarization properties of these modes imply Fm 3̅ m symmetry of the lattice, indicative for on average an ordered distribution of Fe and Na atoms in the lattice. We further show that temperature dependence of the Raman modes, such as changes in the phonon line width and their energies, suggests high phonon anharmonicity, typical for double perovskite materials. Resonant multiphonon Raman scattering reveals the presence of high-lying band states that mediate strong electron–phonon coupling and give rise to intense nA 1 g overtones up to the fifth order. Strong…

High Resolution Image Download MS PowerPoint Slide Lattice defects affect the long-term stability of halide perovskite solar cells. Whereas simple point defects, i.e., atomic interstitials and vacancies, have been studied in great detail, here we focus on compound defects that are more likely to form under crystal growth conditions, such as compound vacancies or interstitials, and antisites. We identify the most prominent defects in the archetype inorganic perovskite CsPbI 3, through first-principles density functional theory (DFT) calculations. We find that under equilibrium conditions at room temperature, the antisite of Pb substituting Cs forms in a concentration comparable to those of the most prominent point defects, whereas the other compound defects are negligible. However, under nonequilibrium thermal and operating conditions, other complexes also become as important as the point defects. Those are the Cs substituting Pb antisite, and, to a lesser extent, the compound vacancies of PbI 2 or CsPbI 3 units, and the I substituting Cs antisite. These compound defects only lead to…

The reactive chemistry of molecular hydrogen at surfaces, notably dissociative sticking and hydrogen evolution, plays a crucial role in energy storage and fuel cells. Theoretical studies can help to decipher underlying mechanisms and reaction design, but studying dynamics at surfaces is computationally challenging due to the complex electronic structure at interfaces and the high sensitivity of dynamics to reaction barriers. In addition, ab initio molecular dynamics, based on density functional theory, is too computationally demanding to accurately predict reactive sticking or desorption probabilities, as it requires averaging over tens of thousands of initial conditions. High-dimensional machine learning-based interatomic potentials are starting to be more commonly used in gas-surface dynamics, yet robust approaches to generate reliable training data and assess how model uncertainty affects the prediction of dynamic observables are not well established. Here, we employ ensemble learning to adaptively generate training data while assessing model performance with full uncertainty…

We examine the borate group intermixing in a series of 25 borosilicate (BS) glasses from the [0.5M(2)O–0.5Na2O]–B2O3–SiO2 systems with M = {Li, K, Rb, Mg, Ca} along with ternary K2O–B2O3–SiO2 and Na2O–B2O3–SiO2 glasses by double-quantum–single-quantum (2Q–1Q) 11B correlation nuclear magnetic resonance (NMR) experiments. The alterations of the fractional populations of B[3]–O–B[3], B[3]–O–B[4], and B[4]–O–B[4] linkages in the glass networks were monitored for variable nSi/nB molar ratios, nonbridging O contents of the glass, and the (average) cation field strength (CFS) of the Mz+/Na+ network modifiers. A significant B[4]–O–B[4] bonding is observed in all glasses, thereby conclusively demonstrating that the normally assumed "BO4–BO4 avoidance" is far from strict in BS glasses, regardless of the Mz+ field strength. We show that the degree of B[4]–O–B[4] bonding depends foremost on its underlying BO4 population and to a lesser degree on the NBO content of the glass; we also provide a straightforward prediction of the B[4]–O–B[4] population in an arbitrary BS glass from parameters…

The decomposition network of AP is essential for the combustion performance and safety of solid propellants, while the detailed reaction pathway during thermolysis is far from clear due to the ultrafast and complex reactions involved. Herein, we present direct atomic simulations of AP thermal decomposition and propose a detailed decomposition network to fill the missing piece in the kinetics models, by using a neural network model derived from ab initio calculations. The proton transfer is the dominant channel (NH4 + ClO4 -> NH3 + HClO4), which is also observed in previous mass spectra experiments. In addition, gas products from decomposition play a critical role in promoting the decomposition of solid AP. For example, the H abstraction reaction by OH is found to be a critical pathway for AP decomposition. These simulations provide atomic insights into the complex reaction dynamics of AP and can be extended to investigate the reaction mechanism of novel energetic materials.

Titanium dioxide (TiO 2 ) is a wide bandgap semiconductor that has a wide range of applications including wastewater treatment, photocatalysis, solar cells, and sensors owing to its excellent electronic and optical properties. However, the wide bandgap of TiO 2 (∼3.2 eV) along with the recombination processes of the photoexcited charge carriers reduce its interfacial charge transport properties and respective activities. Energetics, optical response, and corresponding photophysics of excited charge carriers can be altered through doping and codoping of TiO 2 and composite formulation . Therefore, it is very crucial to understand the structure–property and property-application relationships of doped, co-doped, and composite TiO 2 to maximize the efficiency and extend the fundamental understanding for their applications in different fields. In this Perspective, we summarize the ongoing research on the advancement of undoped, doped, co-doped, and composite TiO 2 including their structure and morphology, energetics, and corresponding photophysics relative to their applications in…

Using seawater for concrete production is potentially advantageous from a sustainability perspective. However, the fundamental mechanisms underlying seawater-mixed concrete are far from being understood, especially from the nanoscale. Herein, molecular models are developed to study, for the first time, the influence of seawater (NaCl solutions) on the behavior of calcium silicate hydrate (C-S-H, the main binding phase of concrete). Thermodynamically, Na + showed a strong adsorption capacity on the C-S-H surface, resulting in the partial release of Ca 2+ from the surface (termed as “Na–Ca cation exchange”). Mechanically, the presence of NaCl in the interlayer solutions enhanced the bond performance between the C-S-H layers because Na + ions provided a greater stress transfer capacity than H 2 O molecules. Under shear loading, the C-S-H layers slid over each other, with the interlayer solutions acting as a lubricant. An increase in NaCl concentration enhanced the sliding resistance, which was attributed to the increased viscosity of the interlayer solutions and strengthening of the…

van der Waals heterostructures (vdWHs) provide a new strategy to broaden the application of two-dimensional (2D) materials in novel nanodevices. Based on first-principles calculations, we propose a 2D MoSi 2 N 4 /MoS 2 vdWH for light harvesting and photovoltaic applications. The MoSi 2 N 4 /MoS 2 vdWH exhibits a semiconducting characteristic with an indirect band gap of 1.12 eV. The type-II band alignment of MoSi 2 N 4 /MoS 2 vdWH facilitates the spatial separation of photogenerated electron–hole pairs. Therefore, the MoSi 2 N 4 /MoS 2 vdWH exhibits excellent optical absorption (∼10 5 cm –1 ) and large photocurrent density (1.6 mA cm –2 ) in the visible range. Furthermore, performing external electric field and biaxial strain can effectively regulate the band gap and band alignment of MoSi 2 N 4 /MoS 2 vdWH. Notably, the tensile strain significantly enhances the optical absorption and total photocurrent of MoSi 2 N 4 /MoS 2 vdWH. These findings reveal the potential of MoSi 2 N 4 /MoS 2 vdWH as a new alternative for optoelectronic devices and provide new possibilities for designing…

The lack of atomic-scale understanding of the dissolution of RuO 2 electrocatalysts for water splitting has hindered the development of durable RuO 2 -based electrocatalysts. In this study, using the first-principles electrochemical nudged elastic band method, we have discovered a facile water oxidation-induced Ru reconstruction and dissolution mechanism at the RuO 2 (110) surface. The potential-dependent activation energies of the dissolution process are well below 1.0 eV at electrode potentials higher than 1.5 V vs SHE. Furthermore, the Ru atoms in the close neighborhood of a Ru vacancy are found to be less prone to dissolution due to their higher oxidation state that could reduce the driving force for water oxidation-induced Ru reconstruction. These findings not only deepen the atomic-scale understandings of the Ru dissolution process but also provide routes for improving the stability of RuO 2 -based water splitting electrocatalysts.

out of electrolyte samples, although this method consumes any HF in the electrolyte solution.

Developing heterogeneous catalysts involves continuous efforts in understanding and designing active sites with improved performance for various applications. In recent years, the recognition and appreciation of the dynamic nature of active sites has permeated the field, leading to renewed efforts in describing dynamic phenomena and exploiting them to go beyond classical barriers of catalyst performance. The challenges in this field are daunting, yet the rewards could lead to new classes of catalysts that outperform traditional systems for critical chemical transformations at the industrial scale. Furthermore, a deeper understanding of the dynamic nature of active sites can lead to fundamental knowledge of practical importance in the field. In this Perspective, we highlight this emerging area of catalysis science using recent examples to motivate the importance of understanding the dynamic nature of heterogeneous catalysts. We predict that this area of study will continue to expand, eventually allowing us to exploit dynamics to control catalytic performance in numerous applications.

High Resolution Image Download MS PowerPoint Slide The demand for efficient gas sensors has fueled research into novel materials such as transition-metal dichalcogenide (TMD) compounds. TMDs such as MoS 2, MoSe 2, and MoTe 2 have shown promise in detecting NO 2 . However, it remains uncertain which one is best suited for this purpose. Consequently, this study employs computational methods to investigate the adsorption of NO 2 on monolayers of MoS 2, MoSe 2, and MoTe 2 . The results show that MoTe 2 exhibits the strongest interaction with the highest charge transfer, suggesting its potential for superior NO 2 detection compared to MoSe 2 and MoS 2 . The sheets share the same type of outward-projecting orbitals, and thus, they also share the principal mode of charge projection. However, the bonding within the sheet influences the accumulation of charge within it, which in turn impacts the availability of electrons on its surface. Subsequently, the mechanism of charge transfer between the TMDs and NO 2 remains the same, but more available charge results in an enhanced adsorption…

Chemical vapor deposited WS 2 monolayers are subjected for the first time to controlled pure biaxial tensile strain up to 0.7%. From photoluminescence (PL) spectroscopy, the trion and neutral exciton deformation potentials are found to be similar, approximately −130 meV/%. It is shown that the excess carrier concentration as well as residual strain in WS 2 samples can be determined from the PL spectra. The experimental Grüneisen parameter of the in-plane E ′ Raman mode for 1L-WS 2 is found to be equal to the corresponding mode ( E 2g ) mode in bulk WS 2 . The impact of mechanical strain on the electronic and phonon band structures is also calculated in the framework of density functional theory. The theoretically obtained deformation potential for the direct transition is in very good agreement with the experiment. The reduced dimensionality of the monolayer enables the visualization over the entire Brillouin zone of both the calculated phonon dispersions and the Grüneisen parameters, which are compared with the experimentally accessible ones. This work contributes to the…

High Resolution Image Download MS PowerPoint Slide Metal halide perovskites have shown extraordinary performance in solar energy conversion technologies. They have been classified as “soft semiconductors” due to their flexible corner-sharing octahedral networks and polymorphous nature. Understanding the local and average structures continues to be challenging for both modeling and experiments. Here, we report the quantitative analysis of structural dynamics in time and space from molecular dynamics simulations of perovskite crystals. The compact descriptors provided cover a wide variety of structural properties, including octahedral tilting and distortion, local lattice parameters, molecular orientations, as well as their spatial correlation. To validate our methods, we have trained a machine learning force field (MLFF) for methylammonium lead bromide (CH 3 NH 3 PbBr 3 ) using an on-the-fly training approach with Gaussian process regression. The known stable phases are reproduced, and we find an additional symmetry-breaking effect in the cubic and tetragonal phases close to the…

A fundamental understanding of the catalytic mechanisms of the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) at applied electrode potentials is crucial for designing bifunctional catalysts. Here, we revisit the OER and ORR on single-atom catalysts (SACs) by using the grand canonical fixed-potential method. It is revealed that the charge states of reaction intermediates are linearly related to the potential through the capacitance and surface area, and different intermediates exhibit different charge states under the same potential, which arises from the adsorption-induced change in the work function and surface dipole. As a result, the charge transfer in each proton-coupled electron-transfer step is no longer 1e –, yielding a deviation of the potential-dependent relative free energy from the simple expression with a linear potential correction as in the conventional computational hydrogen electrode model, further affecting the evaluation of overpotential and catalytic activity. Importantly, the slopes of universal scaling relations decrease linearly with…

Lithium-ion batteries have long been the focus of energy storage. The potential application of carbon-derived structures as lithium-ion battery anodes was examined using the first-principles density functional theory approach. The results of our calculations revealed that the modified lattice constant, structure, and parameters are similar to those found in earlier research. It is worth noting that the twin-graphene double layer has several stable adsorption sites for lithium. Meanwhile, we discovered that the characteristics of semiconductors of pristine twin-graphene changed into metal properties after absorbing lithium. From climbing image nudged elastic band calculations, we got a medium diffusion barrier of 0.42 eV for lithium ion on twin-graphene, which denotes strong diffusivity. Therefore, it has an ultrahigh theoretical capacity of 3916 mAh/g, about 5 times that of graphene (744 mAh/g). Twin-graphene double-layer lithium-ion batteries have an average open circuit voltage of 0.32 V, which ensures long service life and quick charging in practical applications. The relatively…

Co-MOF based metal organic framework was synthesized by reacting a metal ion (cobalt nitrate hexahydrate) with an organic ligand (2-methylimidazole) via a wet chemical method. The resulting material was characterized using detailed analytical methods and further was used as a self-assembly corrosion inhibitor in sweet corrosive environment. The empirical data set via electrochemical studies was modeled using adaptive neuro fuzzy inference system (ANFIS). The observed results showed that Co-MOF could significantly impede the corrosion rate of X65 steel and protect it from CO 2 corrosion. Increasing the concentration of Co-MOF in the test solution increased the inhibition efficiency up to 97% at 0.1 wt % Co-MOF with a mixed-type inhibition mechanism. In addition, the DFT/MD-simulation approach evidenced the adsorption disposition of Co-MOF in aqueous and gas phase which complement with the empirical findings. Also, the prognostic capability of the proposed algorithm based on the statistical parameters such as root-mean-square error (RMSE), chi square (χ 2 ), model predictive error…

In recent years, electrochemical reduction of CO 2 to high-value chemicals and fuels using carbon-based two-dimensional materials has emerged as a promising alternative for reducing the atmospheric CO 2 levels and addressing global energy challenges. However, rationally tuning the electronic structure of these materials for optimizing their catalytic performance remains a great challenge. Herein, using first-principles simulations, we investigate the electronic and catalytic properties of the single atom (SA)-functionalized graphitic carbon nitride (g-C 2 N) monolayer for CO 2 activation and reduction. Our results reveal that SA substitution leads to effective activation and capture of CO 2 . In-depth electronic structure analysis based on the crystal orbital Hamilton population (COHP) and integrated density of states unraveled the atomic-level details of the interaction of CO 2 with the SA-substituted monolayers. Furthermore, the simulated reaction pathways demonstrate that the Al-SAC is highly proficient for CO 2 conversion to HCOOH, whereas the B-SAC reduces CO 2 to CH 3 OH with…

In recent years, molybdenum disulfide nanosheets (MoS 2 NSs) with sulfur surface defects have been used for surface-enhanced Raman scattering (SERS). However, methods to generate sulfur defects on the MoS 2 NS surface are sophisticated and expensive. In this study, we present a relatively straightforward approach to quickly creating sulfur defects on MoS 2 NSs by chemical treatment with NaBH 4 . Few-layered MoS 2 NSs (FL-MoS 2 NSs) were formed by exfoliating bulk-MoS 2 in isopropanol. By oxidation–reduction reactions of FL-MoS 2 NSs mixed with a suitable concentration of NaBH 4, the resulting MoS 2 NSs with abundant sulfur defects (SV-FL-MoS 2 NSs) can be obtained. Spectroscopic and electron microscopic methods are used to demonstrate sulfur defects in SV-FL-MoS 2 NSs. Rhodamine (R6G) and rhodamine-B (RhB) were used as Raman analytes to evaluate the SERS efficiency of SV-FL-MoS 2 NSs. The developed SERS substrate provided detection limits of 1 × 10 –8 M for both R6G and RhB, with enhancement factors of 2.21 × 10 6 and 4.02 × 10 6, respectively. Our measurements of SV-FL-MoS 2 NSs’…

High Resolution Image Download MS PowerPoint Slide Lithium metal batteries are one of the promising technologies for future energy storage. One open challenge is the generation of a stable and well performing Solid Electrolyte Interphase (SEI) between lithium metal and electrolyte. Understanding the complex interaction of reactions at the lithium surface and the resulting SEI is crucial for knowledge-driven improvement of the SEI. This study reveals the internal species distribution and geometrical aspects of the native SEI during formation by model-based analysis. To achieve this, a combination of molecular dynamics, density functional theory, and stand-alone 3D-kinetic Monte Carlo simulations is used. The kinetic Monte Carlo model determines the SEI growth features over a long time and length scale so that the SEI can be analyzed quantitatively. The simulation confirms the frequently postulated layered SEI structure arising from the decomposition of an ethylene carbonate/lithium hexafluorophosphate (2 M) electrolyte with lithium metal. These layers are not clearly separated, which…

The reaction of BiOI to form iodine-poor derivatives under high temperatures was investigated by using temperature-dependent low-wavenumber Raman spectroscopy. The Raman spectra of BiOI and of the iodine-poor derivatives Bi 4 O 5 I 2, Bi 7 O 9 I 3, and Bi 5 O 7 I were recorded. The phonon mode displacement vectors were calculated in the software CRYSTAL, and the PBE0/pob-TZVP method was used to analyze these Raman bands. The appearance of a Raman band at 95 cm –1 of a heated sample of BiOI in the atmosphere was assigned to the production of Bi 4 O 5 I 2, and up to 623 K, no other iodine-poor derivatives were generated. After 632.8 nm laser irradiation under vacuum for a few minutes before exposure to the atmosphere, Bi 7 O 9 I 3 and β-Bi 2 O 3 were produced at various laser powers. Red shifts of low-wavenumber bands with temperature were obtained, and the slopes of the linear dependence χ for three phonon modes of BiOI were obtained. The obtained χ values were more negative in the atmosphere than in a vacuum. This can be explained by the reaction of BiOI to form Bi 4 O 5 I 2, during…

Despite their remarkable properties, many two-dimensional (2D) materials do not possess the desired characteristics to enhance the energy density, rate performance, and cycle life of batteries when used as standalone materials for battery electrodes. However, engineering 2D van der Waals (vdW) heterostructures by stacking different 2D materials offers new opportunities for battery electrodes, combining desirable features and overcoming the limitations of the constituent 2D layers. In this work, using first-principles calculations, we investigated the electronic structure, thermal stability, stress–strain response, alkali (Li/Na/K)-ion adsorption, and diffusion characteristics of 2D heterostructures of titanium disulfide (TiS 2 ) and molybdenum disulfide (MoS 2 ) monolayers with attractive applications in alkali-metal ion batteries (AMIBs). This work revealed relatively strong interlayer interactions in the heterostructure, resulting in significant enhancements in the adsorption of alkali ions compared to the respective monolayers. This work demonstrates that TiS 2 /MoS 2…

Recently, there has been increasing interest in photodynamic therapy (PDT) compared to traditional methods (immunotherapy, surgery, chemotherapy, or radiotherapy) in the treatment of cancer. Also, sonodynamic therapy (SDT) is a non-invasive therapeutic modality that enables high tissue penetration by triggered ultrasound (US). Phthalocyanines (Pcs) are known as one of the most important classes of sensitizers used in PDT and SDT. Motivated by these facts, in this study, to assess potentials for sono-PDT (SPDT), the preparation of peripherally substituted metal-free ( 2 ), zinc ( 3 ), and indium ( 4 ) Pcs was completed by 3-methoxybenzyloxy substituents. The resulting compounds were characterized by applying spectroscopic techniques including 1 H NMR, FT-IR, UV–vis, and MS. In sono–photochemical studies, the calculated singlet oxygen quantum yield (Φ Δ ) values were 0.68 for ZnPc ( 3 ) and 0.83 for InPc ( 4 ) after light irradiation; these values increased to 0.81 for 3 and 0.94 for 4 after combination US and light irradiation. The obtained data proved that the singlet oxygen…

Solid–liquid interfaces are central to a range of interesting phenomena including colloidal aggregation, crystallization by particle attachment, catalysis, heterogeneous nucleation, water desalination, and biomolecular assembly. While three-dimensional atomic force microscopy (3D AFM) has emerged as a technique for resolving interfacial solution structure at the molecular scale, key challenges for data interpretation persist, most notably regarding the influence of the probe on the measured structure. Using the mica–water system as a case study, we investigate the effect of hydrophilic and hydrophobic probes on interfacial solution structure measured by 3D AFM. Data from hydrophilic silicon-based probes are in good agreement with molecular dynamics simulations, wherein the innermost water molecules adsorb preferentially at the surface ditrigonal cavity sites, followed by two additional ordered hydration layers. In contrast, the hydrophobic carbon-based probes detect vertical oscillatory features but do not show lateral patterning that matches the underlying mica lattice. At high…

Herein, we have synthesized three different types of carbon dots, i.e., (a) CDs from citric acid, (b) nitrogen atom functionalized CDs from citric acid and ammonia, and (c) phosphorus atom functionalized CDs from citric acid and sodium dihydrogen orthophosphate through a simple bottom-up carbonization technique. Detailed morphological and elemental features are investigated by high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy study, and it is further correlated to the ongoing photophysical properties. To investigate the specific role of the heteroatom functionalities on the room temperature phosphorescence, we have incorporated all these three types of CDs in a boric acid matrix to diminish the flexibility of surface functional groups and decrease the nonradiative relaxation processes. Various heteroatom functionalities play a very specific role to tune the afterglow properties by altering the energy gap (Δ E ST ) between the lowest excited singlet (S 1 ) and triplet state (T 1 ) and the spin–orbit coupling constant which eventually control the…

P-doping has been widely adopted in M–N–C materials to enhance the catalytic activity of oxygen reduction reaction (ORR). However, the ORR mechanism of P-doping remains elusive. Herein, based on the first-principles calculations, the stability of P-doped FeN 4 is studied, and surface coverage versus potential is determined by the microkinetic model. It is revealed that the O *P coverage is stable at full potential due to the strong oxygen adsorption of P dopants, resulting in the hydrogen bond forming between OH *Fe and O *P . Thereby, the hydrogen-bond-promoted ORR mechanism is discovered. That is, the hydrogen bond between OH *Fe –O *P favors axial OH ligands covering at the broad potential range and thus promotes the ORR performance of FeN 4 both thermodynamically and kinetically. The core of the hydrogen-bond-regulated mechanism is that the oxygen species introduced by doping atoms will impact the ORR process at metal sites, and the methodology can also be applied to study other heteroatom-doped single-atom electrocatalysts.

The sustainable and cost-effective reduction of electrochemical CO 2 to valuable chemicals or fuels is a promising solution to mitigate greenhouse gas emissions and energy demands. Herein, the potential of MXenes as an anchoring site for isolated transition metal (TM) atoms is explored to develop efficient single-atom catalysts (SACs) for the electrochemical CO 2 reduction reaction (CO 2 RR). We design a series of SACs from 3d (Sc, Ti, V, Cr, Mn), 4d (Y, Zr, Nb, Mo), and 5d (Hf) transition metals, supported on an O-terminated MXene (TM@Ti 2 CO 2 ) using well-defined first-principles calculations. Our results show that the TMs anchored on top of the carbon atom of Ti 2 CO 2 (hollow-C site) exhibit the most stable configuration. The electronic calculations demonstrate a strong correlation between adsorption energy and various chemical properties such as average bond distances ( d TM–O ), Bader charge, work function, and d-electron center of the metal, suggesting that the complex interplay between the electronic and geometric properties of the adsorbing atom can serve as descriptors…

All carbon nanoparticles with a developed surface exhibit photoluminescence (PL), the surface origin of which makes it possible to create environmental nanosensors based on it. The active development of sensors for metal ions based on the photoluminescence of carbon dots (CDs) has shown that the quenching of CDs’ photoluminescence can occur due to different mechanisms. However, the magnitude of their contributions to total PL quenching has not been studied. This article presents the results of studies of the mechanisms of photoluminescence quenching in aqueous solutions of carbon dots of hydrothermal synthesis by metal cations: Co 2+, Cu 2+, Mg 2+, Ni 2+, Pb 2+, Zn 2+, Al 3+, Cr 3+, and Fe 3+ . It was established that, for different ions, the following mechanisms make significant contributions to the quenching of the photoluminescence of carbon dots in water: the effect of an inner filter; static quenching due to changes in luminophores caused by (de)protonation of the surface groups of carbon dots with a change of pH value; dynamic quenching. Their contributions to the total…

Li-ion solid-state electrolytes (Li-SSEs) hold promise to solve critical issues related to conventional Li-ion batteries (LIBs), such as the flammability of liquid electrolytes and dendrite growth. In this study, we develop a platform involving a high-throughput screening process and machine learning surrogate model for identifying superionic Li-SSEs among 19,480 Li-containing materials. Li-SSE candidates are selected based on the screening criteria, and their ionic conductivities are predicted. For the training database, the ionic conductivities and crystal systems of various inorganic SSEs, such as Na SuperIonic CONductor (NASICON), argyrodite, and halide, are obtained from previous literature. Subsequently, a chemical descriptor (CD), crystal system, and number of atoms are used as machine-readable features. To reduce the uncertainty in the surrogate model, the ensemble method, which considers the two best-performing models, is employed; the mean prediction accuracies are found to be 0.887 and 0.886, respectively. Furthermore, first-principles calculations are conducted to…

For an energetic material with a definite composition, the substituent position is the most crucial factor to influence its physicochemical properties. Thus, it is becoming increasingly important to understand the impact of positional isomerism on multidimensional properties differences. Herein, we reported two new potential energetic melt-castable molecules, a pair of positional isomers (4-MMDNP and 5-MMDNP). These two explosives exhibit obviously different properties, including densities (Δρ = 0.03 g cm –3 ), melting point (Δ T m = 47.2 °C), decomposition temperature (Δ T d = 27.3 °C), stability (IS = 20 J, FS = 160 N vs IS = 10 J, FS = 40 N), etc., even though they share similar compositions and structures. Simultaneously, by analyzing crystal packing, intermolecular interactions, and monomolecular parameters, we were able to uncover the roots of property differences. Altogether, our results provide comprehensive molecular and crystal level insight into the effect of positional isomerism, which may be useful for new molecular design.

We report on a pump wavelength-dependent study of electron–phonon relaxation in colloidal solutions of isolated gold nanospheres and nanorods. We varied the pump wavelength over a broad spectral range that covers plasmon-resonant and off-resonant excitations in 40 nm gold nanospheres with a plasmon resonance at 525 nm and 34 × 91 nm gold nanorods with a longitudinal plasmon resonance at 720 nm. We also performed an excitation power dependence at each pump wavelength and plotted the measured plasmon bleach recovery kinetics against the initial change in the electron temperature, as obtained from the incident fluence and gold nanoparticle absorption. These plots were all linear and revealed as they intercept the intrinsic electron–phonon relaxation time, which we found to be independent of pump wavelength and hence the same regardless of how the nanoparticles were excited. The plasmon bleach recovery dynamics at a given pump wavelength and excitation power simply describe the collective cooling of a hot thermalized electron distribution with the lattice to reach thermal equilibrium…

Being the most abundant and cleanest form of energy, sunlight is utilized in producing electricity, charging batteries, and more such applications. Though the earth gets a good amount of sunlight on its surface each day, only a small fraction of it gets utilized. It is still a concern for scientists to use the broad spectrum to achieve maximum performance in photocatalysis. In this work, we have developed a series of perovskite oxide (SrTiO 3 )- and MXene (Ti 3 C 2 )-based interfacial heterostructures and decorated them with gold nanoparticles to enable plasmon-mediated electron transfer. These interfacial ternary heterostructures have been successfully utilized for photocatalytic environmental remediation of a colorless pharmaceutical pollutant under natural sunlight irradiation. The remarkable photocatalytic performance of these heterostructures can be attributed to broad-spectrum light harvesting, good charge separation, and quick charge transport. The stability and recyclability of these photocatalysts have also been demonstrated. This work validates that a combination of…

Lithium-ion batteries have dominated the markets of portable devices, electric vehicles, and grid storage. However, the increased safety concerns, range anxiety, and the mismatch between charging time and expectations resulted in a severe hampering of their applications in electric vehicles (EVs). This Perspective focuses on the limiting factors and the recent progress of fast-charging lithium-ion batteries. The limiting factors are discussed from the materials, electrolytes, electrodes, cells, packs, systems, charging stations, and safety issues including the potential impact of fast charging on thermal runaway characteristics. Then, performance optimization strategies from multiscales for fast charging are reviewed. In particular, the key to future fast-charging technologies lies in high-voltage charging techniques and advanced thermal management systems. These technologies can achieve both fast charging and uniform temperature distribution. Finally, the technological gaps are identified and suggestions are made for future research direction, emphasizing the necessity of…

The use of the Jonhson–Mehl–Avrami–Kolomogorov (JMAK) model has become prevalent in the kinetic analysis for Mg-based hydrogen storage alloys. However, the classical JMAK model has shown inadequate results in certain cases, resulting in poor fitness and/or inexplicably low Avrami exponent n . To address this issue, this paper proposes a new model based on the classic JMAK model. The new model considers the preferential growth of the hydride phase from the surface into the bulk, resulting in a diffusion barrier effect during the hydrogenation of Mg-based hydrogen storage alloys. A new parameter, surface diffusion barrier index b, is introduced to quantify the surface diffusion barrier effect. The governing equation is expressed as ln( – ln [1 – Y ( t )]) = n ln k + n ln t – bt . The modified JMAK model demonstrates improved fitting performance for the hydrogenation analysis in multiple Mg-based systems. Additionally, the relationship between diffusion barrier index b and the reaction rate is discussed. The results suggest that the faster initial reaction rate leads to a stronger…

High Resolution Image Download MS PowerPoint Slide BaTiO 3 (BTO) typically demonstrates a strong n-type character with absorption only in the ultraviolet (λ ≤ 390 nm) region. Extending the applications of BTO to a range of fields necessitates a thorough insight into how to tune its carrier concentration and extend the optical response. Despite significant progress, simultaneously inducing visible-light absorption with a controlled carrier concentration via doping remains challenging. In this work, a p-type BTO with visible-light (λ ≤ 600 nm) absorption is realized via iridium (Ir) doping. Detailed analysis using advanced spectroscopy/microscopy tools revealed mechanistic insights into the n- to p-type transition. The computational electronic structure analysis further corroborated this observation. This complementary data helped establish a correlation between the occupancy and the position of the dopant in the band gap with the carrier concentration. A decrease in the Ti 3+ donor-level concentration and the mutually correlated oxygen vacancies upon Ir doping is attributed to the…

The size-dependent pressure response of oleate-stabilized CdSe quantum dots (QDs) in paraffin is investigated using diamond anvil cell experiments and density functional theory (DFT). For QDs above 3.0 nm, the photoluminescence shows a blue-shift of around 43 meV/GPa, close to the value for bulk CdSe, but the shift increases strongly for nanocrystals less than 3 nm in size. Conversely, the absorption shift is 45 meV/GPa above 3.0 nm but weakens to 35 meV/GPa for particles 1.5 nm in size. No crystallographic phase transitions occur below 2 GPa, and the optical effects are reversible. DFT calculations confirm that shifts in the bulk modulus begin for sizes estimated to be 1/2 of the Bohr radius, which we term the extreme confinement regime.

Carbonic anhydrase (CA) is an enzyme with unparallele d catalytic activity in CO 2 hydration. However, its high cost and low stability seriously restrict its industrial application in CO 2 absorption. Constructing CA mimics is a promising strategy to overcome the above limitations. However, to date, a majority of mimics reported are suffering from laborious synthetic processes, harsh synthetic conditions, and costly ligand materials. Therefore, developing novel CA mimics with higher applicability remains a high priority. Due to the structural similarity between zeolite imidazolate framework (ZIF)-8 and natural carbonic anhydrase (CA), ZIF-8 may be considered as a potential CA-mimetic catalyst for CO 2 absorption. To validate this assumption, ZIF-8 and hydrophilic ZIF-8-TA were synthesized and the results from subsequent CO 2 absorption experiments indicated that the synthesized catalysts could significantly enhance CO 2 absorption in water and common alkaline solutions. The addition of 1.0 wt % ZIF-8 in water and different alkaline solutions respectively increased the average CO 2…

Two-dimensional layered nanomaterials (hexagonal boron nitride (h-BN) and expanded graphite (EG)) incorporated poly(vinylidene fluoride) (PVDF) nanocomposites were fabricated via high-shear solution mixing accompanied by compression molding. “Ultrasonication” followed by “centrifugation” was employed to “de-stack” h-BN and EG, which exhibited a decrease in “agglomerate” size in PVDF/h-BN and PVDF/EG nanocomposites. Further, the PVDF/h-BN nanocomposite showed a polar fraction of ∼57% at 0.50 wt % of h-BN concentration with an increased β-phase content, whereas the PVDF/EG nanocomposite showed a higher content of γ-phase as compared to β-phase. Moreover, dielectric investigations indicated that the “ultrasonicated” and “centrifuged” h-BN- and EG-based PVDF nanocomposites exhibit the highest dielectric properties owing to improved interfacial and dipolar polarizations. The piezoelectric strain coefficient of PVDF/0.16BN and PVDF/0.17EG nanocomposites exhibited d 33 values of ∼99 and ∼91 pm/V, respectively. Finally, sensor devices were fabricated based on PVDF/EG and PVDF/h-BN…

The issue of increased reaction resistance due to bubble growth has always been a major bottleneck limiting the efficiency improvement of photoelectrochemical water splitting. In this study, we developed a synchronized measurement system with a micro-high-speed camera and an electrochemical workstation to observe oxygen bubble evolution on the surface of a fixed TiO 2 film electrode in situ. The intrinsic relationship between the nucleation and growth of oxygen bubbles and photocurrent at different pH values (1.0–13.0) was investigated. The results indicate that higher pH can promote bubble nucleation at lower potentials. Additionally, increasing pH from 1.0 to 13.0 at 0.1 V vs Ag/AgCl, the photocurrent in the bubble growth stage increases by about 35 times, and the average period of bubble growth decreases by about 15 times. Compared with pH = 9.0, the gas production rates of pH = 1.0 and pH = 13.0 are improved by 13 times and 22 times at 0.71 V vs RHE, respectively. Then, we developed a force balance model for oxygen bubbles at the anode surface, and the predicted bubble…

Certain highly concentrated electrolytes (HCEs) enhance the charge-transfer reaction rate at the electrode/electrolyte interface in Li-ion batteries. The solvation structure of Li + in HCEs significantly affects the electrochemical interfacial reaction kinetics. However, the effects of different anions on these kinetics have not yet been fully understood. Therefore, in this study, we investigated the effects of anionic species on the liquid structure and electrochemical reactions of HCEs composed of various Li salts and propylene carbonate (PC). Raman spectra revealed that both PC and anions were coordinated to Li + ions in HCEs and that the concentration of uncoordinated (free) PC changed depending on the anionic species. Consequently, the activity of Li + in the electrolyte changed depending on the anionic species. The use of Li salts with weakly Lewis basic anions increased the activity of Li + and decreased the concentration of free PC in HCEs. The activity of Li + in the electrolyte significantly affected the Li + intercalation/deintercalation reaction rate of the LiCoO 2…

High Resolution Image Download MS PowerPoint Slide Machine learning potentials (MLPs) capable of accurately describing complex ab initio potential energy surfaces (PESs) have revolutionized the field of multiscale atomistic modeling. In this work, using an extensive density functional theory (DFT) data set (denoted as Si-ZEO22) consisting of 219 unique zeolite topologies (350,000 unique DFT calculations) found in the International Zeolite Association (IZA) database, we have trained a DeePMD-kit MLP to model the dynamics of silica frameworks. The performance of our model is evaluated by calculating various properties that probe the accuracy of the energy and force predictions. This MLP demonstrates impressive agreement with DFT for predicting zeolite structural properties, energy–volume trends, and phonon density of states. Furthermore, our model achieves reasonable predictions for stress–strain relationships without including DFT stress data during training. These results highlight the ability of MLPs to capture the flexibility of zeolite frameworks and motivate further MLP…

In the face of the current climate emergency and the performance, safety, and cost limitations current state-of-art Li-ion batteries present, solid-state batteries are widely anticipated to revolutionize energy storage. The heart of this technology lies in the substitution of liquid electrolytes with solid counterparts, resulting in potential critical advantages, such as higher energy density and safety profiles. In recent years, antiperovskites have become one of the most studied solid electrolyte families for solid-state battery applications as a result of their salient advantages, which include high ionic conductivity, structural versatility, low cost, and stability against metal anodes. This Review highlights the latest progress in the computational design of Li- and Na-based antiperovskite solid electrolytes, focusing on critical topics for their development, including high-throughput screening for novel compositions, synthesizability, doping, ion transport mechanisms, grain boundaries, and electrolyte-electrode interfaces. Moreover, we discuss the remaining challenges facing…

Inorganic halide perovskite nanocrystals (NCs) have drawn considerable attention in recent years due to their improved stability, superior photophysical properties, and defect-tolerant nature, which allows for high carrier mobility and efficient charge transport in various optoelectronic devices. The bandgap and size of halide perovskite nanocrystals can be tuned through a variety of approaches, including cation/anion exchange, ligand modification, and precursor concentration adjustment. In this article, we investigate the effects of precursor concentration on the structural, optical, and electronic properties of cesium lead bromide (CsPbBr 3 ) nanocrystals. We have synthesized ∼13–50 nm nanocrystals from four different concentrations of precursor solutions. It has been observed that the excitonic absorption band increases with particle size as the precursor concentration decreases. The steady state photoluminescence intensity decreases due to a shorter carrier lifetime (in solution). We have fabricated photodetectors using four different-size samples and show that the…

High Resolution Image Download MS PowerPoint Slide The electrochemical reduction of CO 2 (CO 2 RR) is a sustainable alternative for producing fuels and chemicals, although the production of highly desired hydrocarbons is still a challenge due to the higher overpotential requirement in combination with the competitive hydrogen evolution reaction (HER). Tailoring the electrolyte composition is a possible strategy to favor the CO 2 RR over the HER. In this work we studied the solvent effect on the CO 2 RR on a nanostructured Cu electrode in acetonitrile solvent with different amounts of water. Similar to what has been observed for aqueous media, our online gas chromatography results showed that CO 2 RR in acetonitrile solvent is also structure-dependent, since nanocube-covered copper (CuNC) was the only surface (in comparison to polycrystalline Cu) capable of producing a detectable amount of ethylene (10% FE), provided there is enough water present in the electrolyte (>500 mM). In situ Fourier Transform Infrared (FTIR) spectroscopy showed that in acetonitrile solvent the presence of CO…

High Resolution Image Download MS PowerPoint Slide Molecular and oligomeric amines supported in porous oxide supports are a promising class of CO 2 sorbent materials studied for CO 2 removal from diverse streams such as flue gas and ambient air. Among the various amines investigated, low molecular weight, hyperbranched poly(ethyleneimine) (PEI), and tetraethylenepentamine (TEPA) are among the most extensively studied. While macroscopic structure–performance relationships relating the support structure, amine loading, and other factors affecting CO 2 sorption capacities and kinetics have been developed, structural and dynamic information about the organic amine phase in the porous support is less plentiful. The structure and mobility of amines impregnated in the pores of porous supports directly impact gas sorption, as the accessibility of amine sites in the pores directly relates to amine distribution in the pores and overall pore filling as well as the dynamics of the amine chains. Here, we prepare a family of mesoporous silica SBA-15 materials containing varying loadings of…

Abnormal dopamine levels severely affect the functioning of the central nervous system, and it is imperative to design a suitable sensor to diagnose the disease at the earliest. Metal–organic frameworks (MOFs) with high surface area and pore tunability have attracted wide attention in sensing applications. In this work, a Zr-NDI-based MOF and its composite Zr-NDI/MWCNT have been studied for the dual sensing of dopamine using fluorescence and electrochemical techniques in an aqueous phosphate buffer solution. The limit of detection (LOD) of 2 μM and 0.6 μM was achieved using MOF and Zr-NDI/MWCNT with fluorescence microscopy and differential pulse voltammetry (DPV) methods, respectively. The sensor shows excellent selectivity and sensitivity in the presence of the most common interfering analytes, such as uric acid and ascorbic acid. Notably, the sensor also displayed remarkable stability with almost 95% retention in the recyclability tests and a good recovery rate (99–105%) in the presence of a real urine sample.

To address the low capacity and poor stability of aqueous zinc–iodine batteries owing to the insulating nature of iodine and the shuttle effect of polyiodide, herein, tungsten nitride-modified porous carbon polyhedron (W 2 N/N-C) was prepared via the pyrolysis of ZIF-8 injected with phosphotungstic acid (PTA@ZIF-8). During the thermal treatment process, the self-nitridation enabled the in situ formation of tungsten nitride nanoparticles in hierarchical porous carbon with nitrogen doping for favorable loading of iodine. When used as the electrode material, the zinc–iodine battery exhibited the low polarization during the charge/discharge process with improved reversibility and good cycling stability for 2000 cycles. The improved electrochemical performance would be attributed to the confinement effect of W 2 N/N-C for the reversible conversion between iodine and polyiodide, thus enhancing the redox reversibility and utilization of active materials. The present work demonstrates an efficient strategy to prepare porous carbon with metal nitrides via the combination of carbonization and…

Electrochemical reduction is a potential solution to eliminate nitrate in wastewater; however, the poor activity and product selectivity of traditional electrocatalysts impede its large-scale application. Herein, we report a new catalyst of Cu-modified Ru nanoparticles (Cu-modified Ru/C NPs) prepared by underpotential deposition (UPD) of Cu atoms onto Ru NPs, which shows good nitrate reduction kinetics and NH 3 selectivity. To unravel the enhancing mechanism, the impact of Cu coverage on nitrate reduction and the formation of possible products/intermediates as well as the competition of side products H 2 have been investigated systematically by tracking the reverse oxidation of such species using rotation ring disk electrode (RRDE) combined with cyclic voltammetry. Our results reveal that the Cu-modified Ru/C NPs perform NH 3 yield of 23.7 μmol h –1 cm –2 and 95% Faradaic efficiency, which is better than Ru/C NPs (6.0 μmol h –1 cm –2 with Faradaic efficiency of 66%); This enhancement of modified Cu atoms toward nitrate reduction results from synergetic effects: (i) Cu blocks the…

Characterizing nanoparticles (NPs) is crucial in nanoscience due to the direct influence of their physiochemical properties on their behavior. Various experimental techniques exist to analyze the size and shape of NPs, each with advantages, limitations, proneness to uncertainty, and resource requirements. One of them is electron microscopy (EM), often considered the gold standard, which offers visualization of the primary particles. However, despite its advantages, EM can be expensive, less accessible, and difficult to apply during dynamic processes. Therefore, using EM for specific experimental conditions, such as observing dynamic processes or visualizing low-contrast particles, is challenging. This study showcases the potential of machine learning in deriving EM parameters by utilizing cost-effective and dynamic techniques such as dynamic light scattering (DLS) and UV-vis spectroscopy. Our developed model successfully predicts the size and shape parameters of gold NPs based on DLS and UV-vis results. Furthermore, we demonstrate the practicality of our model in situations in which…

Thermally activated delayed fluorescence (TADF) materials have attracted much attention due to their high performance in organic light-emitting diodes (OLEDs). However, progress in developing novel TADF materials is limited by the low-efficiency traditional trial-and-error experimental approach. In this work, by integrating machine learning (ML) and quantum mechanics (QM) calculations, we have achieved fast prediction of high-efficiency TADF emitters. 44470 molecules are first generated by virtually combining common 49 donor and 50 acceptor fragments. The ML model is trained for predicting molecular properties by using the QM results of 5136 molecules. Finally, by applying it, 384 molecules are rapidly screened out of 39334 molecules as potential TADF emitters. To validate these results, the photophysical parameters of 18 out of 384 molecules are calculated from first-principles calculations, and the obtained TADF rates are greater than 10 4 s –1, even up to 10 6 s –1, suggesting excellent TADF properties. Moreover, the TADF performance of the predicted candidates overwhelms that of…

High Resolution Image Download MS PowerPoint Slide Aqueous electrolytes used in CO 2 electroreduction typically have a CO 2 solubility of around 34 mM under ambient conditions, contributing to mass transfer limitations in the system. Non-aqueous electrolytes exhibit higher CO 2 solubility (by 5–8-fold) and also provide possibilities to suppress the undesired hydrogen evolution reaction (HER). On the other hand, a proton donor is needed to produce many of the products commonly obtained with aqueous electrolytes. This work investigates the electrochemical CO 2 reduction performance of copper in non-aqueous electrolytes based on dimethylformamide (DMF), n -methyl-2-pyrrolidone (NMP), and acetonitrile (ACN). The main objective is to analyze whether non-aqueous electrolytes are a viable alternative to aqueous electrolytes for hydrocarbon production. Additionally, the effects of aqueous/non-aqueous anolytes, membrane, and the selection of a potential window on the electrochemical CO 2 reduction performance are addressed in this study. Experiments with pure DMF and NMP mainly produced…

Since their first appearance, electrode potential/solution pH charts (Pourbaix diagrams) have served as a general framework for the analysis of material corrosion in aqueous solutions. Their utility in describing electrochemical stability of materials is rooted in the equilibrium thermodynamics based formalism. Electrochemical energy systems, however, do not always operate under thermodynamic equilibrium conditions, and corrosion itself is an inherently irreversible interfacial process. In this Perspective, we highlight a number of representative studies drawn primarily from (photo)electrocatalysis research and aimed to account for the effects of potentiodynamic polarization and transient dissolution, interfacial electrochemical reactions, formation and stability of metastable phases, strain-induced corrosion, as well as the kinetics of dissolution and phase transformations. Some theoretical approaches that can help disentangle corrosion mechanisms under conditions relevant to electrochemical energy conversion applications are briefly discussed. We also advocate for more research…

Herein, we study the structural and electronic origins of molecular adsorption using experiments and density functional theory (DFT) calculations. We performed X-ray diffraction (XRD) and temperature-programmed desorption (TPD) of CO2 on amorphous zirconia (am-ZrO2) and crystalline (tetragonal and monoclinic) zirconia. Using molecular dynamics simulations, the bulk structures of am-ZrO2 and am-zirconium(IV) hydroxide (am-Zr(OH)4) were obtained and the reproducibility of the experimental structure was confirmed by comparing the radial distribution functions. In addition, the hydroxyl density on the hydrogenated ZrO2 surfaces was found to be consistent with the experimental results. Both experiments and simulations indicate that the adsorption of CO2 on an am-ZrO2 surface is more heterogeneous and weaker than that on a crystalline zirconia surface. Because the charge environment and band structures of crystalline zirconia are approximately the same as those of am-ZrO2, the weak adsorption on the am-ZrO2 surface arises from the fewer and stronger Zr-O bonds on the surface. These…

Photocatalytic hydrogen production technology is considered as an important approach to solve the problem of energy shortage. The ZnO@ZnS core–shell nanostructure can not only protect the nuclear material from chemical corrosion but also form heterojunctions to improve the catalytic performance; however, the photocatalysis of ZnO@ZnS only responds to the UV region, and its solar light utilization is low. In this paper, ZnO@ZnS rods were prepared and formed covalent bonding in the interface because of the in situ sulfidation process. Subsequently, the two-dimensional NiAl-LDH with positive charge was grown on the surface of ZnO@ZnS by electrostatic self-assembly due to the presence of negatively charged ZnS. So, the prepared ZnO@ZnS@NiAl-LDH composites have the stable interface structure. We compared the hydrogen production efficiency of ZnO, ZnO@ZnS, and ZnO@ZnS@NiAl-LDH under simulated sunlight. The maximum hydrogen production efficiency of the ZnO@ZnS@NiAl-LDH composite was 866.35 μmol g –1 h –1, which was 3.96 times higher than that of ZnO@ZnS (218.41 μmol g –1 h –1 ), and the…

The search for two-dimensional (2D) magnetic materials has attracted a great deal of attention because of the experimental synthesis of 2D CrI 3, which has a measured Curie temperature of 45 K. Often times, these monolayers have a higher degree of electron correlation and require more sophisticated methods beyond density functional theory (DFT). Diffusion Monte Carlo (DMC) is a correlated electronic structure method that has been demonstrated to be successful for calculating the electronic and magnetic properties of a wide variety of 2D and bulk systems, since it has a weaker dependence on the Hubbard parameter ( U ) and density functional. In this study, we designed a workflow that combines DFT+U and DMC in order to treat 2D correlated magnetic systems. We chose monolayer CrX 3 (X = I, Br, Cl, F), with a stronger focus on CrI 3 and CrBr 3, as a case study due to the fact that they have been experimentally realized and have a finite critical temperature. With this DFT+U and DMC workflow and the analytical method of Torelli and Olsen, we estimated a maximum value of 43.56 K for the T…

MoTe 2 has been experimentally and theoretically identified as a promising cathode candidate for electrocatalytic CO 2 reduction (CO2RR). A full understanding of its reactivity requires special consideration of the reaction kinetics, but this is challenging due to the varying electrode potential in the canonical density functional theory (DFT), which calls for grand canonical, constant potential methods. Here, the full reaction pathways for the CO2RR to CO and the competing hydrogen evolution reaction (HER) are investigated on a MoTe 2 edge in an alkaline medium using a grand canonical ensemble DFT approach with a hybrid solvent model to understand the explicit effect of the applied potential. Our results show that the barrier of the first CO2RR step, the CO 2 adsorption, is lower than the first HER step, the Volmer step, which implies that the CO2RR is favored. We also find that at more negative potentials, the first CO2RR steps become more favorable, whereas CO desorption becomes less favorable, indicating that further CO reduction is expected instead of CO desorption. However,…

This study explores the mysteries of the oxygen-evolution reaction (OER) in the presence of Ni(Fe) (hydr)oxides and examines the effects of Ni and Fe impurities on the reaction. The current methods for removing Fe impurities could complicate the study of OER. A crucial aspect of this study is the reinvestigation of Ni (hydr)oxides in a Ni/Fe-free electrolyte during the OER. It is widely recognized that a Ni (hydr)oxide phase, possessing an active phase for the OER, forms on the surface of Ni foil in the presence of air, even in the absence of any applied potential. It is observed that after Fe saturation on the electrode surface, additional Fe has no significant impact on the OER when Ni foil is present. Furthermore, the presence of additional Ni(II) (hydr)oxide does not significantly influence the OER of the Ni foil. However, the OER activity is enhanced when Fe impurities are introduced into the Ni foil. In the Ni/Fe-free electrolyte, the OER current decreases due to the conversion of Ni(II) (hydr)oxide, and the activity of Ni foil results in reduced OER activity due to increased…

High Resolution Image Download MS PowerPoint Slide Quantum-well (QW) hybrid organic–inorganic perovskite (HOIP) crystals, e.g., A 2 PbX 4 (A = BA, PEA; X = Br, I), demonstrated significant potentials as scintillating materials for wide energy radiation detection compared to their individual three-dimensional (3D) counterparts, e.g., BPbX 3 (B = MA). Inserting 3D into QW structures resulted in new structures, namely A 2 BPb 2 X 7 perovskite crystals, and they may have promising optical and scintillation properties toward higher mass density and fast timing scintillators. In this article, we investigate the crystal structure as well as optical and scintillation properties of iodide-based QW HOIP crystals, A 2 PbI 4 and A 2 MAPb 2 I 7 . A 2 PbI 4 crystals exhibit green and red emission with the fastest PL decay time <1 ns, while A 2 MAPb 2 I 7 crystals exhibit a high mass density of >3.0 g/cm 3 and tunable smaller bandgaps <2.1 eV resulting from quantum and dielectric confinement. We observe that A 2 PbI 4 and PEA 2 MAPb 2 I 7 show emission under X- and γ-ray excitations. We further…

Functionalized aniline, as an important class of intermediates in industrial production, is in increasing demand in the course of rapid industrial and economic development. Hydrogenation of nitroarenes with low prices and wide sources to produce aniline is one of the most important means. Among them, catalytic hydrogenation is currently the dominant industrial production method in this field, while the electrocatalytic hydrogenation driven by renewable energy power generation is more promising in the context of current sustainable development. Aiming at the problems existing in the industrial production of nitroarene hydrogenation, this Review first sorts out the development process of relevant catalysts mainly from the two aspects of improving selectivity and reducing costs. Then, we have also compiled in situ characterizations and theoretical calculations for related mechanistic studies as well as a class of soluble redox mediators that can facilitate the electrochemical hydrogenation process. Finally, some of the issues that still need to be addressed in this research field are…

This Article provides new insights concerning the simulation of plasmon-driven chemical reactions using real-time TDDFT based on the tight-binding electronic structure code DFTB+, with applications to the dissociation of H 2 on octahedral silver and gold nanoparticles with 19–489 atoms. A new component of these calculations involves sampling a 300 K canonical ensemble to determine the distribution of possible outcomes of the calculations, and with this approach we are able to determine the threshold for dissociation as a function of laser intensity, wavelength, and nanocluster size. We show that the threshold intensity varies as an inverse power of nanocluster size, which makes it possible to extrapolate the results to sizes that are more typical of experimental studies. The intensities obtained from this extrapolation are around a factor of 100 above powers used in the pulsed experiments. This is a closer comparison of theory and experiment than has been obtained in previous real-time simulations, and the remaining discrepancy can be understood in terms of electromagnetic hot spots…

Phenothiazine- and tetraphenylethylene (TPE)-based mechanochromic materials ( PTZTPE-1CHO, PTZTPE-4CHO, and PTZTPE-4CN ) with different electron-withdrawing substituents (−CHO and −CN) were designed and synthesized by the Suzuki cross-coupling reaction of bromo-TPEs with the corresponding boronate esters of phenothiazine. The photophysical, aggregation-induced emission, mechanochromic, thermal, and electroluminescence properties of the synthesized compounds were investigated. The cyano group-bearing derivative PTZTPE-4CN exhibited reversible mechanochromism, and its emission maximum shifted bathochromically when mechanically ground, whereas the formyl group-containing derivatives PTZTPE-1CHO and PTZTPE-4CHO exhibited hypsochromically shifted mechanochromism. The solution of PTZTPE-4CN was weakly emissive, and PTZTPE-1CHO and PTZTPE-4CHO exhibit strong fluorescence in the solution state due to the intramolecular charge transfer transitions. The electroluminescence properties of the synthesized compounds as non-annealed and annealed non-doped prompt fluorescent emitters were studied…