The 50 most-cited articles in Advanced Functional Materials, 2018

Abstract The ever‐growing demands for electrical energy storage have stimulated the pursuit of alternative advanced batteries. Zn‐ion batteries (ZIBs) are receiving increased attentions due to the low cost, high safety, and high eco‐efficiency. However, it is still a big challenge to develop suitable cathode materials for intercalation of Zn ions. This review provides a timely access for researchers to the recent activities regarding ZIBs. First, cathode materials including various manganese oxides, vanadium compounds, and Prussian blue analogs are summarized with details in crystal structures and Zn ion storage mechanisms. Then, the electrolytes and their influences on the electrochemical processes are discussed. Finally, opinions on the current challenge of ZIBs and perspective to future research directions are provided.

Abstract 2D material based photodetectors have attracted many research projects due to their unique structures and excellent electronic and optoelectronic properties. These 2D materials, including semimetallic graphene, semiconducting black phosphorus, transition metal dichalcogenides, insulating hexagonal boron nitride, and their various heterostructures, show a wide distribution in bandgap values. To date, hundreds of photodetectors based on 2D materials have been reported. Here, a review of photodetectors based on 2D materials covering the detection spectrum from ultraviolet to infrared is presented. First, a brief insight into the detection mechanisms of 2D material photodetectors as well as introducing the figure‐of‐merits which are key factors for a reasonable comparison between different photodetectors is provided. Then, the recent progress on 2D material based photodetectors is reviewed. Particularly, the excellent performances such as broadband spectrum detection, ultrahigh photoresponsivity and sensitivity, fast response speed and high bandwidth, polarization‐sensitive…

Abstract Exploring cheap and efficient cocatalysts for enhancing the performance of photocatalysts is a challenge in the energy conversion field. Herein, 2D ultrathin Ti 3 C 2 nanosheets, a kind of MXenes, are prepared by etching Ti 3 AlC 2 with subsequent ultrasonic exfoliation. A novel 2D/2D heterojunction of ultrathin Ti 3 C 2 /Bi 2 WO 6 nanosheets is then successfully prepared by in situ growth of Bi 2 WO 6 ultrathin nanosheets on the surface of these Ti 3 C 2 ultrathin nanosheets. The resultant Ti 3 C 2 /Bi 2 WO 6 hybrids exhibit a short charge transport distance and a large interface contact area, assuring excellent bulk‐to‐surface and interfacial charge transfer abilities. Meanwhile, the improved specific surface area and pore structure endow Ti 3 C 2 /Bi 2 WO 6 hybrids with an enhanced CO 2 adsorption capability. As a result, the 2D/2D heterojunction of ultrathin Ti 3 C 2 /Bi 2 WO 6 nanosheets shows significant improvement on the performance of photocatalytic CO 2 reduction under simulated solar irradiation. The total yield of CH 4 and CH 3 OH obtained on the optimized Ti 3…

Abstract Covalent organic frameworks (COFs) are crystalline porous polymers formed by a bottom‐up approach from molecular building units having a predesigned geometry that are connected through covalent bonds. They offer positional control over their building blocks in two and three dimensions. This control enables the synthesis of rigid porous structures with a high regularity and the ability to fine‐tune the chemical and physical properties of the network. This Feature Article provides a comprehensive overview over the structures realized to date in the fast growing field of covalent organic framework development. Different synthesis strategies to meet diverse demands, such as high crystallinity, straightforward processability, or the formation of thin films are discussed. Furthermore, insights into the growing fields of COF applications, including gas storage and separations, sensing, electrochemical energy storage, and optoelectronics are provided.

Abstract Developing sustainable and renewable energy sources along with efficient energy storage and conversion technologies is vital to address environmental and energy challenges. Electrochemical water splitting coupling with grid‐scale renewable energy harvesting technologies is becoming one of the most promising approaches. Besides, hydrogen with the highest mass‐energy density of any fuel is regarded as the ultimate clean energy carrier. The realization of practical water splitting depends heavily on the development of low‐cost, highly active, and durable catalysts for hydrogen evolution reactions (HERs) and oxygen evolution reactions (OERs). Recently, heterostructured catalysts, which are generally composed of electrochemical active materials and various functional additives, have demonstrated extraordinary electrocatalytic performance toward HER and OER, and particularly a number of precious‐metal‐free heterostructures delivered comparable activity with precious‐metal‐based catalysts. Herein, an overview is presented of recent research progress on heterostructured HER…

Abstract 4D printing has attracted tremendous interest since its first conceptualization in 2013. 4D printing derived from the fast growth and interdisciplinary research of smart materials, 3D printer, and design. Compared with the static objects created by 3D printing, 4D printing allows a 3D printed structure to change its configuration or function with time in response to external stimuli such as temperature, light, water, etc., which makes 3D printing alive. Herein, the material systems used in 4D printing are reviewed, with emphasis on mechanisms and potential applications. After a brief overview of the definition, history, and basic elements of 4D printing, the state‐of‐the‐art advances in 4D printing for shape‐shifting materials are reviewed in detail. Both single material and multiple materials using different mechanisms for shape changing are summarized. In addition, 4D printing of multifunctional materials, such as 4D bioprinting, is briefly introduced. Finally, the trend of 4D printing and the perspectives for this exciting new field are highlighted.

Abstract Dielectric capacitors, which store electrical energy in the form of an electrostatic field via dielectric polarization, are used in pulsed power electronics due to their high power density and ultrashort discharge time. In pursuit of developing high‐performance dielectric capacitors, special attention has been given to the improvement of their energy density and storage efficiency, which would make them useful for an even wider variety of applications. Among the different dielectric materials studied so far, including polymers, glasses, and both bulk and film‐based ceramics, dielectric ceramic films, which are of particular interest for miniature power electronics and mobile platforms, have demonstrated the greatest energy storage performances. In this regard, several interesting approaches involving physical, chemical, and microstructural modifications of the dielectric ceramic films are adopted. In addition to a brief discussion of the polymers, glasses, and ceramics used in dielectric capacitors and key parameters related to their energy storage performance, this review…

Abstract High conductivity, large mechanical strength, and elongation are important parameters for soft electronic applications. However, it is difficult to find a material with balanced electronic and mechanical performance. Here, a simple method is developed to introduce ion‐rich pores into strong hydrogel matrix and fabricate a novel ionic conductive hydrogel with a high level of electronic and mechanical properties. The proposed ionic conductive hydrogel is achieved by physically cross‐linking the tough biocompatible polyvinyl alcohol (PVA) gel as the matrix and embedding hydroxypropyl cellulose (HPC) biopolymer fibers inside matrix followed by salt solution soaking. The wrinkle and dense structure induced by salting in PVA matrix provides large stress (1.3 MPa) and strain (975%). The well‐distributed porous structure as well as ion migration–facilitated ion‐rich environment generated by embedded HPC fibers dramatically enhances ionic conductivity (up to 3.4 S m −1 , at f = 1 MHz). The conductive hybrid hydrogel can work as an artificial nerve in a 3D printed robotic hand,…

Abstract 3D hierarchical heterostructure NiFe LDH@NiCoP/NF electrodes are prepared successfully on nickel foam with special interface engineering and synergistic effects. This research finds that the as‐prepared NiFe LDH@NiCoP/NF electrodes have a more sophisticated inner structure and intensive interface than a simple physical mixture. The NiFe LDH@NiCoP/NF electrodes require an overpotential as low as 120 and 220 mV to deliver 10 mA cm−2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1 m KOH, respectively. Tafel and electrochemical impedance spectroscopy further reveal a favorable kinetic during electrolysis. Specifically, the NiFe LDH@NiCoP/NF electrodes are simultaneously used as cathode and anode for overall water splitting, which requires a cell voltage of 1.57 V at 10 mA cm−2. Furthermore, the synergistic effect of the heterostructure improves the structural stability and promotes the generation of active phases during HER and OER, resulting in excellent stability over 100 h of continuous operation. Moreover, the strategy and interface…

Abstract Although multifunctional, flexible, and wearable textiles with integrated smart electronics have attracted tremendous attention in recent years, it is still an issue to balance new functionalities with the inherent performances of the textile substrates. 2D early transition metal carbides/nitrides (MXenes) are considered as ideal nanosheets for fabricating multifunctional and flexible textiles on the basis of their superb intrinsic electrical conductivity, tunable surface chemistry, and layered structure. Herein, highly conductive and hydrophobic textiles with exceptional electromagnetic interference (EMI) shielding efficiency and excellent Joule heating performance are fabricated by depositing in situ polymerized polypyrrole (PPy) modified MXene sheets onto poly(ethylene terephthalate) textiles followed by a silicone coating. The resultant multifunctional textile exhibits high electrical conductivity of ≈1000 S m−1 in conjunction with an exceptional EMI shielding efficiency of ≈90 dB at a thickness of 1.3 mm. The thin silicone coating renders the hydrophilic…

Abstract Flexible electronics, as an emerging and exciting research field, have brought great interest to the issue of how to make flexible electronic materials that offer both durability and high performance at strained states. With the advent of on‐body wearable and implantable electronics, as well as increasing demands for human‐friendly intelligent soft robots, enormous effort is being expended on highly flexible functional materials, especially stretchable electrodes, by both the academic and industrial communities. Among different deformation modes, stretchability is the most demanding and challenging. This review focuses on the latest advances in stretchable transparent electrodes based on a new design strategy known as kirigami (the art of paper cutting) and investigates the recent progress on novel applications, including skin‐like electronics, implantable biodegradable devices, and bioinspired soft robotics. By comparing the optoelectrical and mechanical properties of different electrode materials, some of the most important outcomes with comments on their merits and…

Abstract Multifunctionalization is the future development direction for microwave absorbing materials, but has not yet been explored. The effective integration of multiple functions into one material remains a huge challenge. Herein, an aerogel‐type microwave absorber assembled with multidimensional organic and inorganic components is synthesized. Polyacrylonitrile fibers and polybenzoxazine membranes work as the skeleton and crosslinker, respectively, forming a 3D framework, in which carbon nanotubes are interconnected into an electrically conductive network, and Fe 3 O 4 nanoparticles are uniformly dispersed throughout the aerogel. Remarkably, the microwave absorption performances of the aerogel achieve ultralight, ultrathin (1.5 mm), and strong absorption (reflection loss of −59.85 dB) features. In particular, its specific reflection loss values considerably outperform the current magnetic–dielectric hybrids with similar components. Moreover, the aerogel possesses strong hydrophobicity and good thermal insulation, endowing it attractive functions of self‐cleaning, infrared…

Abstract 2D halide perovskites have recently been recognized as a promising avenue in perovskite solar cells (PSCs) in terms of encouraging stability and defect passivation effect. However, the efficiency (less than 15%) of ultrastable 2D Ruddlesden–Popper PSCs still lag far behind their traditional 3D perovskite counterparts. Here, a rationally designed 2D‐3D perovskite stacking‐layered architecture by in situ growing 2D PEA 2 PbI 4 capping layers on top of 3D perovskite film, which drastically improves the stability of PSCs without compromising their high performance, is reported. Such a 2D perovskite capping layer induces larger Fermi‐level splitting in the 2D‐3D perovskite film under light illumination, resulting in an enhanced open‐circuit voltage ( V oc ) and thus a higher efficiency of 18.51% in the 2D‐3D PSCs. Time‐resolved photoluminescence decay measurements indicate the facilitated hole extraction in the 2D‐3D stacking‐layered perovskite films, which is ascribed to the optimized energy band alignment and reduced nonradiative recombination at the subgap states. Benefiting…

Abstract The bifunctional electrocatalysis of oxygen reduction reactions (ORRs) and oxygen evolution reactions (OERs) is critical for the development of rechargeable Zn–air batteries. Both ORRs and OERs suffer from sluggish kinetics and high overpotentials, and the bifunctional reactivity is limited by the scaling relationship. Therefore, smart designs on electrocatalysts are requested to achieve high bifunctional ORR/OER activity and excellent performance in Zn–air batteries. Herein, the requirements for bifunctional oxygen electrocatalysts are first introduced. Then the recent advances of precious‐metal‐free active materials and regulation methods of their intrinsic activity are introduced. The structural design principles to improve the accessibility of the active sites are further presented. Finally, a brief overview of the applications of bifunctional oxygen electrocatalysts in Zn–air batteries, including routine liquid batteries and flexible solid‐state batteries, is presented. This review affords rational design principles and strategies for nonprecious bifunctional ORR/OER…

Abstract 2D Nanomaterials, with unique structural and electronic features, have shown enormous potential toward photocatalysis fields. However, the photocatalytic behavior of pristine 2D photocatalysts are still unsatisfactory, and far below the requirements of practical applications. In this regard, surface defect engineering can serve as an effective means to tune photoelectric parameters of 2D photocatalysts through tailoring the local surface microstructure, electronic structure, and carrier concentration. In this review, recent progress in the design of surface defects with the classified anion vacancy, cation vacancy, vacancy associates, pits, distortions, and disorder on 2D photocatalysts to boost the photocatalytic performance is summarized. The strategies for controlling defects formation and technique to distinguish various surface defects are presented. The crucial roles of surface defects for photocatalysis performance optimization are proposed and advancement of defective 2D photocatalysts toward versatile applications such as water oxidation, hydrogen production, CO 2…

Abstract Electromagnetic wave (EM) absorption materials with broader effective absorption bandwidth (EAB), lightweight, and thinness characteristics are highly desirable in areas of wearable device and portable electronics. However, there are still many obstacles to simultaneously satisfy the above critical requirements required by new high‐performance EM absorption materials. Herein, for the first time, Ti 3 C 2 T X MXenes are selected as the dielectric mediator to prepare reduced graphene oxide (RGO)/Ti 3 C 2 T X hybrids foam with hollow core–shell architectures and controllable complex permittivity via self‐assembly and sacrificial template processes, under the guidance of theoretical calculations. RGO is grafted flatly on the outer surface of the Ti 3 C 2 T X spheres‐core, forming a unique heterostructure. The RGO/Ti 3 C 2 T X foam possesses excellent EM absorption performance superior to all reported foam‐based counterparts, the EAB covers the whole X‐band at 3.2 mm while the density is merely 0.0033 g cm −3 , and its specific EM absorption performance ( SMAP = RL (dB)/…

Abstract Nanodiamonds exhibit great potential as green catalysts for remediation of organic contaminants. However, the specific active site and corresponding oxidative mechanism are unclear, which retard further developments of high‐performance catalysts. Here, an annealing strategy is developed to accurately regulate the content of ketonic carbonyl groups on nanodiamonds; meanwhile other structural characteristics of nanodiamonds remain almost unchanged. The well‐defined nanodiamonds with well‐controlled ketonic carbonyl groups exhibit excellent catalytic activity in activation of peroxymonosulfate for oxidation of organic pollutants. Based on the semi‐quantitative and quantitative correlations of ketonic carbonyl groups and the reaction rate constants, it is conclusively determined that ketonic carbonyl groups are the catalytically active sites. Different from conventional oxidative systems, reactive oxygen species in nanodiamonds@peroxymonosulfate system are revealed to be singlet oxygen with high selectivity, which can effectively oxidize and mineralize the target contaminants.…

Abstract Metal–organic frameworks (MOFs) and MOF‐derived nanostructures are recently emerging as promising catalysts for electrocatalysis applications. Herein, 2D MOFs nanosheets decorated with Fe‐MOF nanoparticles are synthesized and evaluated as the catalysts for water oxidation catalysis in alkaline medium. A dramatic enhancement of the catalytic activity is demonstrated by introduction of electrochemically inert Fe‐MOF nanoparticles onto active 2D MOFs nanosheets. In the case of active Ni‐MOF nanosheets (Ni‐MOF@Fe‐MOF), the overpotential is 265 mV to reach a current density of 10 mA cm −2 in 1 m KOH, which is lowered by ≈100 mV after hybridization due to the 2D nanosheet morphology and the synergistic effect between Ni active centers and Fe species. Similar performance improvement is also successfully demonstrated in the active NiCo‐MOF nanosheets. More importantly, the real catalytic active species in the hybrid Ni‐MOF@Fe‐MOF catalyst are unraveled. It is found that, NiO nanograins (≈5 nm) are formed in situ during oxygen evolution reaction (OER) process and act as OER active…

Abstract The vast market demands for applications of organic light‐emitting diodes (OLEDs) have quickened the pace of the search for future high‐performance materials, emphasizing the importance of exploring blue light‐emitting materials, which determine the performance bottleneck of OLEDs. Moreover, actualizing highly efficient, pure‐blue, stable, and purely organic electroluminescence will pave the way toward the realization of cost‐effective, high‐quality, and long‐lasting commercialized OLED displays and illumination applications. Without the aid of noble heavy metal atoms, the newly emerging thermally activated delayed fluorescent (TADF) materials can effectively utilize triplet excitons owing to the small singlet–triplet splitting energy (ΔEST) for rapid reverse intersystem crossing (RISC) process, leading to the achievement of 100% internal quantum efficiency under electrical operation. Nevertheless, fundamental scientific challenges with respect to simultaneously achieving stable pure‐blue emission, large radiative recombination rates with short exciton lifetimes and small…

Abstract Developing a feasible and efficient separation membrane for the purification of highly emulsified oily wastewater is of significance but challenging due to the critical limitations of low flux and serious membrane fouling. Herein, a biomimetic and superwettable nanofibrous skin on an electrospun fibrous membrane via a facile strategy of synchronous electrospraying and electrospinning is created. The obtained nanofibrous skin possesses a lotus‐leaf‐like micro/nanostructured surface with intriguing superhydrophilicity and underwater superoleophobicity, which are due to the synergistic effect of the hierarchical roughness and hydrophilic polymeric matrix. The ultrathin, high porosity, sub‐micrometer porous skin layer results in the composite nanofibrous membranes exhibiting superior performances for separating both highly emulsified surfactant‐free and surfactant‐stabilized oil‐in‐water emulsions. An ultrahigh permeation flux of up to 5152 L m −2 h −1 with a separation efficiency of >99.93% is obtained solely under the driving of gravity (≈1 kPa), which was one order of…

Abstract Aqueous zinc‐ion batteries have been considered as potential energy storage devices owing to their high safety and low cost. Traditional zinc‐ion batteries often implement a typical Zn2+ insertion/extraction mechanism. Compared with traditional Zn2+ insertion/extraction mechanism, supercapacitor‐liked dual‐ion mechanism often endow the batteries with higher operating voltage, better rate capability, and longer cycle life. Herein, aqueous Zn/polyaniline batteries are developed, which can combine the Zn2+ insertion/extraction and dual‐ion mechanisms. The Zn/polyaniline batteries deliver excellent electrochemical performance, especially a long cycle life up to 3000 cycles with high‐capacity retention of 92%. This hybrid mechanism provides a promising battery chemistry. Furthermore, Zn/polyaniline batteries can be assembled into quasi‐solid‐state soft‐packaged and cable‐type configurations and display stable electrochemical performance even under different bending states, showing potential applications for flexible electronics.

Abstract Lithium (Li) metal has been pursued as “Holy Grail” among various anode materials due to its high specific capacity and the lowest reduction potential. However, uncontrolled growth of Li dendrites and extremely unstable interfaces during repeated Li plating/stripping ineluctably plague the practical applications of Li metal batteries. Herein, an artificial protective layer with synergistic soft–rigid feature is constructed on the Li metal anode to offer superior interfacial stability during long‐term cycles. By suppressing random Li deposition and the formation of isolated Li, such a protective layer enables a dendrite‐free morphology of Li metal anode and suppresses the depletion of Li metal and electrolyte. Additionally, sufficient ionic conductivity is guaranteed through the synergy between soft and rigid structural units that are uniformly dispersed in the layer. Dendrite‐free and dense Li deposition, as well as a greatly reduced interfacial resistance after cycling, is achieved owing to the stabilized interface, accounting for significantly prolonged cycle life of Li…

Abstract Hydrogel materials are receiving increasing research interest due to their intriguing structures that consist of a crosslinked network of polymer chains with interstitial spaces filled with solvent water. This feature endows the materials with the characteristics of being both wet and soft, making them ideal candidates for electrolyte materials for flexible energy storage devices, such as supercapacitors and rechargeable batteries that are under intensive studies nowadays. More importantly, the highly abundant and tunable chemistries of these hydrogels allow the introduction of novel functionalities into the existing hydrogels so that it is possible to fabricate unprecedented energy storage devices with additional functions. Here, the state‐of‐the‐art advances of the hydrogel materials for flexible energy storage devices including supercapacitors and rechargeable batteries are reviewed. In addition, devices with various kinds of functions, such as self‐healing, shape memory, and stretchability, are also included to stress the critical role of hydrogel materials.…

Abstract SnO 2 has been well investigated in many successful state‐of‐the‐art perovskite solar cells (PSCs) due to its favorable attributes such as high mobility, wide bandgap, and deep conduction band and valence band. Several independent studies show the performances of PSCs with SnO 2 are higher than that with TiO 2 , especially in device stability. In 2015, the first planar PSCs were reported with a power conversion efficiency over 17% using a low temperature sol‐derived SnO 2 nanocrystal electron transport layer (ETL). Since then, many other groups have also reported high performance PSCs based on SnO 2 ETLs. SnO 2 planar PSCs show currently the highest performance in planar configuration devices (21.6%) and are close to the record holder of TiO 2 mesoporous PSCs, suggesting their high potential as ETLs in PSCs. The main concerns with the application of SnO 2 as ETL are that it suffers from degradation in high temperature processes and that its much lower conduction band compared to perovskite may result in a voltage loss of PSCs. Here, notable achievements to date are…

Abstract The topic of sustainable and eco‐friendly energy storage technologies is an issue of global significance. To date, this heavy burden is solely addressed by lithium‐ion battery technology. However, the ongoing depletion of limited global lithium resources has restricted their future availability for Li‐ion battery technology, and hence, a significant price increase is expected. This grim situation is the driving force for the development of the “beyond Li‐ion battery” strategy involving alternatives that have several advantages over conventional Li‐ion batteries in terms of cost, durability, safety, and sustainability. Potassium, the closest neighboring alkali element after sodium, offers some unique advantages over lithium and sodium as a charge carrier in rechargeable batteries. Potassium intercalation chemistry in potassium‐ion batteries (KIBs) is successfully demonstrated to be compatible with Li‐ion batteries and sodium‐ion batteries. In addition to KIBs, potassium–sulfur and potassium–oxygen batteries have emerged as new energy‐storage systems due to their low costs…

Abstract The fast growth of portable smart electronics and internet of things have greatly stimulated the demand for miniaturized energy storage devices. Micro‐supercapacitors (MSCs), which can provide high power density and a long lifetime, are ideal stand‐alone power sources for smart microelectronics. However, relatively few MSCs exhibit both high areal and volumetric capacitance. Here rapid production of flexible MSCs is demonstrated through a scalable, low‐cost stamping strategy. Combining 3D‐printed stamps with arbitrary shapes and 2D titanium carbide or carbonitride inks (Ti 3 C 2 T x and Ti 3 CNT x , respectively, known as MXenes), flexible all‐MXene MSCs with controlled architectures are produced. The interdigitated Ti 3 C 2 T x MSC exhibits high areal capacitance: 61 mF cm −2 at 25 µA cm −2 and 50 mF cm −2 as the current density increases by 32 fold. The Ti 3 C 2 T x MSCs also showcase capacitive charge storage properties, good cycling lifetime, high energy and power densities, etc. The production of such high‐performance Ti 3 C 2 T x MSCs can be easily scaled up by…

Abstract Layered double hydroxides (LDHs) are a class of functional anionic clays, which consist of positively charged host layers (brucite‐like M(OH) 6 octahedra) and interlayer anions. By virtue of their unique combination of structural features (including the tunability of both host layers and interlayer guest anion, exfoliation property, structure topological transformation, confinement effect), LDHs have many potential applications in heterogeneous catalysis—as catalysts themselves, catalyst supports, or catalyst precursors. In addition, the properties of LDH‐based catalysts can be tailored for specific purposes by facile modulation of their surface/interface defect structure (e.g., oxygen vacancy defects or metal defects), controlling the concentration/strength of surface acid/base sites, tuning the geometric/electronic structure of active sites, or by taking advantage of the confinement effect intrinsic to 2D materials. In addition, by utilizing the topological structural transformation of LDH precursors, supported metal catalysts can be obtained (as single metals, bimetallic…

Abstract Hard carbons (HCs) possess high lithium/sodium storage capacities, which however suffer from low electric conductivity and poor ion diffusion kinetics. An efficient structure design with appropriate heteroatoms doping and optimized graphitic/defective degree is highly desired to tackle these problems. This work reports a new design of N‐doped HC nanoshells (N‐GCNs) with homogeneous defective nanographite domains, fabricated through the prechelation between Ni2+ and chitosan and subsequent catalyst confined graphitization. The as‐prepared N‐GCNs deliver a high reversible lithium storage capacity of 1253 mA h g−1, with outstanding rate performance (175 mA h g−1 at a high rate of 20 A g−1) and good cycling stability, which outperforms most state‐of‐the‐art HCs. Meanwhile, a high reversible sodium storage capacity of 325 mA h g−1 is also obtained, which stabilizes at 174 mA h g−1 after 200 cycles. Density functional theory calculations are performed to uncover the coupling effect between heteroatom‐doping and the defective nanographitic domains down to the atomic scale. The in…

Abstract Architectural windows that smartly regulate indoor solar radiation by changing their optical transmittance in response to thermostimuli are developed as a promising solution toward reducing the energy consumption of buildings. Recently, energy‐efficient smart window technology has attracted increasing scientific interest, with the exploration of energy‐efficient novel materials as well as integration with practical techniques to generate various desired multifunctionalities. This review systematically summarizes emerging thermoresponsive materials for smart window applications, including hydrogels, ionic liquids, perovskites, metamaterials, and liquid crystals. These are compared with vanadium dioxide (VO 2 ), a conventional and extensively studied material for thermochromic smart window applications. In addition, recent progress on cutting‐edge integrated techniques for smart windows is covered, including electrothermal techniques, self‐cleaning, wettability, and also integration with solar cells for bifunctional energy conservation and generation. Finally, opportunities…

Abstract In this study, a binary networked conductive hydrogel is prepared using acrylamide and polyvinyl alcohol. Based on the obtained hydrogel, an ultrastretchable pressure sensor with biocompatibility and transparency is fabricated cost effectively. The hydrogel exhibits impressive stretchability (>500%) and superior transparency (>90%). Furthermore, the self‐patterned microarchitecture on the hydrogel surface is beneficial to achieve high sensitivity (0.05 kPa −1 for 0–3.27 kPa). The hydrogel‐based pressure sensor can precisely monitor dynamic pressures (3.33, 5.02, and 6.67 kPa) with frequency‐dependent behavior. It also shows fast response (150 ms), durable stability (500 dynamic cycles), and negligible current variation (6%). Moreover, the sensor can instantly detect both tiny (phonation, airflowing, and saliva swallowing) and robust (finger and limb motions) physiological activities. This work presents insights into preparing multifunctional hydrogels for mechanosensory electronics.

Abstract High‐performance graphene microwave absorption materials are highly desirable in daily life and some extreme situations. A simple technique for the direct growth of graphene as absorption fillers in wave‐transmitting matrices is of paramount importance to bring it to real‐world application. Herein, a simple chemical vapor deposition (CVD) route for the direct growth of edge‐rich graphene (ERG) with tailored structures and tunable dielectric properties in porous Si 3 N 4 ceramics using only methyl alcohol (CH 3 OH) as precursor is reported. The large O/C atomic ratio of CH 3 OH helps to build a mild oxidizing atmosphere and leads to a unique structure featuring open graphite nanosteps and freestanding nanoplanes, endowing the ERG/Si 3 N 4 hybrid with an appropriate balance between good impedance matching and strong loss capacity. Accordingly, the prepared materials exhibit superior electromagnetic wave absorption, far surpassing that of traditional CVD graphene and reduced graphene oxide‐based materials, achieving an effective absorption bandwidth of 4.2 GHz covering the…

Abstract Recent technological advances in nanomaterials have driven the development of high‐performance light‐emitting devices with flexible and stretchable form factors. Deformability in such devices is mainly achieved by replacing the rigid materials in the device components with flexible nanomaterials and their assemblies (e.g., carbon nanotubes, silver nanowires, graphene, and quantum dots) or with intrinsically soft materials and their composites (e.g., polymers and elastomers). Downscaling the dimensions of the functional materials to the nanometer range dramatically decreases their flexural rigidity, and production of polymer/elastomer composites with functional nanomaterials provides light‐emitting devices with flexibility and stretchability. Furthermore, monolithic integration of these light‐emitting devices with deformable sensors furnishes the resulting display with various smart functions such as force/capacitive touch‐based data input, personalized health monitoring, and interactive human–machine interfacing. These ultrathin, lightweight, and deformable smart…

Abstract Lightweight, flexible, and electrically conductive thin films with high electromagnetic interference (EMI) shielding effectiveness are highly desirable for next‐generation portable and wearable electronic devices. Here, spin spray layer‐by‐layer (SSLbL) to rapidly assemble Ti 3 C 2 T x MXene‐carbon nanotube (CNT) composite films is shown and their potential for EMI shielding is demonstrated. The SSLbL technique allows strategic combinations of nanostructured materials and polymers providing a rich platform for developing hierarchical architectures with desirable cross‐functionalities including controllable transparency, thickness, and conductivity, as well as high stability and flexibility. These semi‐transparent LbL MXene‐CNT composite films show high conductivities up to 130 S cm −1 and high specific shielding effectiveness up to 58 187 dB cm 2 g −1 , which is attributed to both the excellent electrical conductivity of the conductive fillers (i.e., MXene and CNT) and the enhanced absorption with the LbL architecture of the films. Remarkably, these values are among the…

Abstract All‐solid‐state lithium metal battery is the most promising next‐generation energy storage device. However, the low ionic conductivity of solid electrolytes and high interfacial impedance with electrode are the main factors to limit the development of all‐solid‐state batteries. In this work, a low resistance–integrated all‐solid‐state battery is designed with excellent electrochemical performance that applies the polyethylene oxide (PEO) with lithium bis(trifluoromethylsulphonyl)imide as both binder of cathode and matrix of composite electrolyte embedded with Li7La3Zr2O12 (LLZO) nanowires (PLLN). The PEO in cathode and PLLN are fused at high temperature to form an integrated all‐solid‐state battery structure, which effectively strengthens the interface compatibility and stability between cathode and PLLN to guarantee high efficient ion transportation during long cycling. The LLZO nanowires uniformly distributed in PLLN can increase the ionic conductivity and mechanical strength of composite electrolyte efficiently, which induces the uniform deposition of lithium metal,…

Abstract Fouling caused by oil and other pollutants is one of the most serious challenges for membranes used for oil/water separation. Aiming at improving the comprehensive antifouling property of membranes and thus achieving long‐term cyclic stability, it is reported in this work the design of a kind of zwitterionic nanosized hydrogels grafted poly(vinylidene fluoride) (PVDF) microfiltration membrane (ZNG‐g‐PVDF) with superior fouling‐tolerant property for oil‐in‐water emulsion separation. Sulfobetaine zwitterionic nanohydrogels with the diameter of ≈50 nm are synthesized by an inverse microemulsion polymerization process. They are then grafted onto the surface of PVDF microfiltration membrane, endowing the membrane a superhydrophilic and nearly zero oil adhesion property. This ZNG‐g‐PVDF membrane exhibits great tolerance and resistance to salts pH, especially an excellent antifouling property to oil‐in‐water emulsions containing various pollutants such as surfactants, proteins, and natural organic materials (e.g., humic acid). The comprehensive antifouling property of the membrane…

Abstract Solar steam generation is regarded as one of the most sustainable techniques for desalination and wastewater treatment. However, there has been a lack of scalable material systems with high efficiency under 1 Sun. A solar steam generation device is designed utilizing crossplane water transport in wood via nanoscale channels and the preferred thermal transport direction is decoupled to reduce the conductive heat loss. A high steam generation efficiency of 80% under 1 Sun and 89% under 10 Suns is achieved. Surprisingly, the crossplanes perpendicular to the mesoporous wood can provide rapid water transport via the pits and spirals. The cellulose nanofibers are circularly oriented around the pits and highly aligned along spirals to draw water across lumens. Meanwhile, the anisotropic thermal conduction of mesoporous wood is utilized, which can provide better insulation than widely used super‐thermal insulator Styrofoam (≈0.03 W m−1 K−1). The crossplane direction of wood exhibits a thermal conductivity of 0.11 W m−1 K−1. The anisotropic thermal conduction redirects the absorbed…

Abstract Developing active, robust, and nonprecious electrocatalysts for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) is highly crucial and challenging. In this work, a facile strategy is developed for scalable fabrication of dicobalt phosphide (Co 2 P)–cobalt nitride (CoN) core–shell nanoparticles with double active sites encapsulated in nitrogen‐doped carbon nanotubes (Co 2 P/CoN‐in‐NCNTs) by straight forward pyrolysis method. Both density functional theory calculation and experimental results reveal that pyrrole nitrogen coupled with Co 2 P is the most active one for HER, while Co–N–C active sites existing on the interfaces between CoN and N‐doped carbon shells are responsible for the ORR and OER activity in this catalyst. Furthermore, liquid‐state and all‐solid‐state Zn–air batteries are equipped. Co 2 P/CoN‐in‐NCNTs show high power density as high as 194.6 mW cm −2 , high gravimetric energy density of 844.5 W h kg −1 , very low charge–discharge polarization, and excellent reversibility of 96 h at 5 mA cm −2 in…

Abstract Polymer‐based materials have evoked increasing attention in the research field of room‐temperature phosphorescence (RTP) because they can not only possess fantastic properties such as good flexibility, easy processing, low cost, high thermal stability and so forth, but also serve as rigid matrices to suppress the nonradiative decay process and thus contribute to phosphorescence emission at room temperature. This Review outlines the development of RTP in organic polymer‐based materials from the perspective of nondoped and doped polymer systems, containing the detailed photophysical properties, luminescent mechanisms and their applications. The conclusion and outlook are presented to point out the advances and challenges for further study of polymer‐based metal‐free RTP materials.

Abstract Long‐range ordering of dipoles is a key microscopic signature of ferroelectrics. These ordered dipoles form ferroelectric domains, which can be reoriented by electric fields. Relaxor ferroelectrics are a type of ferroelectric where the long‐range ordering of dipoles is disrupted by cation disorder, exhibiting complex polar states with a significant amount of local structural heterogeneity at the nanoscale. They are the materials of choice for numerous devices such as capacitors, nonlinear optical devices, and piezoelectric transducers, owing to their extraordinary dielectric, electro‐optic, and electromechanical properties. However, despite their extensive applications in these devices, the origins of their unique properties are yet to be fully understood, hindering the design and exploration of new relaxor ferroelectric‐based materials. Herein, the complex polar states and applications of relaxor ferroelectrics are first introduced. Attention is then focused on their electromechanical properties, where the relationship between local structural heterogeneity and the…

Abstract Serotonin (5‐hydroxytryptamine, HT), a neurotransmitter, and its main metabolite 5‐hydroxyindole‐3‐acetic acid (HIAA) are biomarkers for carcinoid tumors. They can be quantitatively detected by a new luminescent sensor based on a water stable lanthanide metal–organic framework (Ln‐MOF). This Ln‐MOF features a (3,4)‐connected topology containing 1D channels occupied by lattice water molecules. Luminescent studies reveal that high luminescence quenching efficiency occurs upon the addition of HT and HIAA. The Ln‐MOF also displays excellent sensitivity with fast response within 1 min, good reusability, and detection limits as low as 0.66 and 0.54 × 10 −6 m for HT and HIAA, respectively. In addition, the sensing function exhibits excellent selectivity even in the presence of other neurotransmitters and the main coexisting species in blood plasma and urine.

Abstract Actuators that can convert environmental stimuli into mechanical work are widely used in intelligent systems, robots, and micromechanics. To produce robust and sensitive actuators of different scales, efforts are devoted to developing effective actuating schemes and functional materials for actuator design. Carbon‐based nanomaterials have emerged as preferred candidates for different actuating systems because of their low cost, ease of processing, mechanical strength, and excellent physical/chemical properties. Especially, due to their excellent photothermal activity, which includes both optical absorption and thermal conductivities, carbon‐based materials have shown great potential for use in photothermal actuators. Herein, the recent advances in photothermal actuators based on various carbon allotropes, including graphite, carbon nanotubes, amorphous carbon, graphene and its derivatives, are reviewed. Different photothermal actuating schemes, including photothermal effect–induced expansion, desorption, phase change, surface tension gradient creation, and actuation under…

Abstract Nonlayered materials are constructed with chemical covalent bonds in all three dimensions, distinct from layered materials, which contain evident structural differences in the horizontal and vertical directions. As a consequence, liquid‐phase exfoliation (LPE), a widely explored technique to obtain 2D layered nanoarchitectures, has not yet been fully characterized for the realization of 2D nonlayered nanostructures. Herein, by virtue of a typical chain‐like structure of crystalline bulk Te with strong TeTe covalent bonds in intrachains and weak Van der Waals forces in interchains, ultrathin 2D nonlayered Te nanosheets are realized by means of an LPE method. The resultant 2D Te nanosheets possess a broad lateral dimension ranging from 41.5 to 177.5 nm and a thickness ranging from 5.1 to 6.4 nm, and its photoresponse properties are evaluated using photoelectrochemical measurements. The 2D Te nanosheets exhibit excellent photoresponse behaviors from the UV to the visible regime in association with strong time and cycle stability for the on/off switching behaviors. The…

Abstract Palladium diselenide (PdSe 2 ), a thus far scarcely studied group‐10 transition metal dichalcogenide has exhibited promising potential in future optoelectronic and electronic devices due to unique structures and electrical properties. Here, the controllable synthesis of wafer‐scale and homogeneous 2D PdSe 2 film is reported by a simple selenization approach. By choosing different thickness of precursor Pd layer, 2D PdSe 2 with thickness of 1.2–20 nm can be readily synthesized. Interestingly, with the increase in thickness, obvious redshift in wavenumber is revealed by Raman spectroscopy. Moreover, in accordance with density functional theory (DFT) calculation, optical absorption and ultraviolet photoemission spectroscopy (UPS) analyses confirm that the PdSe 2 exhibits an evolution from a semiconductor (monolayer) to semimetal (bulk). Further combination of the PdSe 2 layer with Si leads to a highly sensitive, fast, and broadband photodetector with a high responsivity (300.2 mA W −1 ) and specific detectivity (≈10 13 Jones). By decorating the device with black phosphorus…

Abstract Developing bifunctional efficient electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is in high demand for the development of overall water‐splitting devices. In particular, the electrocatalytic performance can be largely improved by designing positive nanoscale‐heterojunction with well‐tuned interfaces. Herein, a novel top‐down strategy is reported to construct the oxide/sulfide heterostructures (N‐NiMoO4/NiS2 nanowires/nanosheets) as a multisite HER/OER catalyst. Starting with the NiMoO4 nanowires, nitridation in a controlled manner enables activation of Ni sites in NiMoO4 and then yields oxide/sulfide heterojunction by directly vulcanizing the highly composition‐segregated N‐NiMoO4 nanowires. The abundant epitaxial heterogeneous interfaces at atomic‐level facilitate the electron transfer from N‐NiMoO4 to NiS2, which further cooperate synergistically toward both the hydrogen and oxygen generation in alkali solution. Furthermore, with N‐NiMoO4/NiS2 grown carbon fiber cloth as the engineering electrode, the assembled…

Abstract Lead halide perovskites show excellent optoelectronic properties but are unsatisfactory in terms of stability and toxicity. Herein, bismuth (Bi)‐doped lead‐free inorganic perovskites Cs2SnCl6:Bi are reported as blue emissive phosphors. Upon Bi doping, the originally nonluminous Cs2SnCl6 exhibits a highly efficient deep‐blue emission at 455 nm, with a Stokes shift of 106 nm and a high photoluminescence quantum yield (PLQY) close to 80%. Hybrid density functional theory calculations suggest the preferred formation of [BiSn+VCl] defect complex, which is believed to be responsible for the optical absorption and the associated blue emission. The Cs2SnCl6:Bi also shows impressive thermal and water stability due to its inorganic nature and the formation of protective BiOCl layer. White light‐emitting diodes (LEDs) are constructed using Cs2SnCl6:Bi and commercial yellow phosphors combined with commercial UV LED chips, giving the Commission Internationale de I'Eclairage (CIE) color coordinates of (0.36, 0.37). This work represents a significant step toward the realization of highly…

Abstract Zeolitic imidazole frameworks (ZIFs) offer rich platforms for rational design and construction of high‐performance nonprecious‐metal oxygen reduction reaction (ORR) catalysts owing to their flexibility, hierarchical porous structures, and high surface area. Herein, an Fe, Cu‐coordinated ZIF‐derived carbon framework (Cu@Fe‐N‐C) with a well‐defined morphology of truncated rhombic dodecahedron is facilely prepared by introducing Fe2+ and Cu2+ during the growth of ZIF‐8, followed by pyrolysis. The obtained Cu@Fe‐N‐C, with bimetallic active sites, large surface area, high nitrogen doping level, and conductive carbon frameworks, exhibits excellent ORR performance. It displays 50 mV higher half‐wave potential (0.892 V) than that of Pt catalysts in an alkaline medium and comparable performance to Pt catalysts in an acidic medium. In addition, it also has excellent durability and methanol resistance ability in both acidic and alkaline solutions, which makes it one of the best Pt‐free catalysts reported to date for ORR. Impressively, when being employed as a cathode catalyst in…

Abstract 2D materials' membranes with well‐defined nanochannels are promising for precise molecular separation. Herein, the design and engineering of atomically thin 2D MXene flacks into nanofilms with a thickness of 20 nm for gas separation are reported. Well‐stacked pristine MXene nanofilms are proven to show outstanding molecular sieving property for H2 preferential transport. Chemical tuning of the MXene nanochannels is also rationally designed for selective permeating CO2. Borate and polyethylenimine (PEI) molecules are well interlocked into MXene layers, realizing the delicate regulation of stacking behaviors and interlayer spacing of MXene nanosheets. The MXene nanofilms with either H2‐ or CO2‐selective transport channels exhibit excellent gas separation performance beyond the limits for state‐of‐the‐art membranes. The mechanisms within these nanoconfined MXene layers are discussed, revealing the transformation from “diffusion‐controlled” to “solution‐controlled” channels after chemical tuning. This work of precisely tailoring the 2D nanostructure may inspire the exploring of…

Abstract Electronic synaptic devices are important building blocks for neuromorphic computational systems that can go beyond the constraints of von Neumann architecture. Although two‐terminal memristive devices are demonstrated to be possible candidates, they suffer from several shortcomings related to the filament formation mechanism including nonlinear switching, write noise, and high device conductance, all of which limit the accuracy and energy efficiency. Electrochemical three‐terminal transistors, in which the channel conductance can be tuned without filament formation provide an alternative platform for synaptic electronics. Here, an all‐solid‐state electrochemical transistor made with Li ion–based solid dielectric and 2D α‐phase molybdenum oxide (α‐MoO 3 ) nanosheets as the channel is demonstrated. These devices achieve nonvolatile conductance modulation in an ultralow conductance regime (<75 nS) by reversible intercalation of Li ions into the α‐MoO 3 lattice. Based on this operating mechanism, the essential functionalities of synapses, such as short‐ and long‐term synaptic…

Abstract Antibacterial materials that prevent bacterial infections and mitigate bacterial virulence have attracted great scientific interests. In recent decades, the bactericidal polymers have been presented as promising candidates to combat bacterial pathogens, mainly based on the construction of bactericidal cationic polymers, functionalization with biocidal agents, and formation of bacterial‐repelling layers. However, these established strategies have inherent disadvantages because they often overlook important features such as their biocompatibility and biosafety, especially for biomedical applications. In recent years, many efforts have been made focusing on the development of multifunctional antibacterial materials to meet the elaborate requirements for medical devices and public hygiene products. Herein the recent advances in developing multifunctional materials for their antibacterial activities together with other functions including “kill‐and‐release” capability, hemocompatibility, cell proliferation promoting properties, and coagulation promoting ability for wound…

Abstract Lithium–sulfur batteries have great potential to satisfy the increasing demand of energy storage systems for portable devices, electric vehicles, and grid storage because of their extremely high specific capacity, cost‐effectiveness, and environmental friendliness. In spite of all these merits, the practical utilization of lithium–sulfur batteries is impeded by commonly known challenges, such as low sulfur utilization (<80%), short life (<200 cycles), fast capacity fade, and severe self‐discharge effect, which mainly result from the i) low conductivity of the active material, ii) serious polysulfide shuttling, iii) large volume changes, and iv) lithium–metal anode contamination/corrosion. Numerous approaches are reported to effectively mitigate these issues. Indeed, such approaches have shown enhanced lithium–sulfur battery performances. However, many reports overlook the critical parameters, including sulfur loading (<13 mg cm −2 ), sulfur content (<70 wt%), and electrolyte/sulfur ratio (>11 µL mg −1 ), that significantly affect the analyzed electrochemical…