Showing papers in "Small structures in 2022"

2D MXene Nanomaterials: Synthesis, Mechanism, and Multifunctional Applications in Microwave Absorption

Abstract: MXene nanomaterials stand out among 2D nanomaterials and have been extensively studied by researchers because of their unique layered structure, chemical diversity, and outstanding chemical and physical properties. In recent years, MXene materials have rapidly opened the market for electromagnetic interference shielding technology due to their excellent electromagnetic wave absorption (EMA) capability. However, so far, compared with the development of electromagnetic (EM) shielding technology, there is still much room for development in the construction of MXenes and the application of electromagnetic wave absorption. Herein, the construction strategies, electromagnetic wave conversion mechanism, and applications of MXenes materials are reviewed. Through meticulous material design and an interdisciplinary approach, 2D MXene materials are expected to become one of the smart tunable wave absorbers, and their application scenarios will also become broader.

Current Progress in 2D Metal–Organic Frameworks for Electrocatalysis

Abstract: The 2D nanosheets of metal–organic frameworks (MOFs) have recently emerged as a promising material that makes them valuable in widespread electrocatalytic fields due to their atomic‐level thickness, abundant active sites, and large surface area. Efficient electrocatalysts for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting are highly desired with low overpotentials to promote the industrial applications of energy conversion and devices. 2D MOF nanostructures provide long‐term stability and high electrical conductivity to enhance catalyst activity and durability. This review briefly summarizes the synthesis and electrocatalytic applications of 2D MOF for HER/OER/water splitting. More attention is focused on the synthetic strategies of 2D MOF and their derivatives. The catalytic performance and superior properties of these materials are highlighted. The outperformance of these materials originates from the rational design, myriad of abundant active sites, and atomic‐level thickness. The current and future challenges in this field and the scientific perspectives to overcome these challenges are highlighted. It is suggested that the construction of 2D MOF nanostructures can develop a state‐of‐the‐art electrocatalyst in energy and environmental division.

Mainstream Optimization Strategies for Cathode Materials of Sodium‐Ion Batteries

Abstract: Sodium‐ion batteries are promising candidates for grid‐scale energy storage due to its abundance and similarities to lithium‐ion batteries, whereas the lack of ideal cathode materials limits their practical development. Apart from exploring novel materials, applying optimization strategies on existing potential cathode materials is demonstrated to be effective and efficient in improving their electrochemical properties toward their theoretical best capabilities. Reported strategies include element doping, surface coating, morphology and structure design, defect engineering, etc. Herein, focusing on oxide and polyanionic cathode materials, a comprehensive and systematic review on emerging optimization strategies is provided by discussing representative studies of each. Corresponding fundamental principles, their applicable ranges, and common influences on properties are analyzed. Finally, the perspectives on the current impediments and future directions in the field are presented.

Atomically Dispersed Metal‐Based Catalysts for Zn–CO2 Batteries

Abstract: Rechargeable aqueous Zn–CO2 batteries show great promise in meeting severe environmental problems and energy crises due to their combination of CO2 utilization and energy output, as well as advantages of high theoretical energy density, abundant raw materials, and high safety. Developing high‐efficiency and stable CO2 reduction reaction (CO2RR) electrocatalysts is of critical importance for the promotion of this technology. Atomically dispersed metal‐based catalysts (ADMCs), with extremely high atom‐utilization efficiency, tunable coordination environments, and superior intrinsic catalytic activity, are emerging as promising candidates for Zn–CO2 batteries. Herein, some recent developments in atomically dispersed metal‐based catalysts for Zn–CO2 batteries are summarized, including transition metal and non‐transition metal sites. Moreover, various synthetic strategies, characterization methods, and the relationship between active site structures and CO2RR activity/Zn–CO2 battery performance are introduced. Finally, some challenges and perspectives are also proposed for the future development of ADMCs in Zn–CO2 batteries.

Embedding Metal–Organic Frameworks for the Design of Flexible Hybrid Supercapacitors by Electrospinning: Synthesis of Highly Graphitized Carbon Nanofibers Containing Metal Oxide Nanoparticles

Abstract: Electrospun carbonaceous fibers have emerged as promising electrode materials for application in energy storage devices. However, their relatively poor electrical conductivity (due to their amorphous carbon structures) and low capacitive performance lead to poor prospects for their further application. Herein, a universal synthesis of highly graphitized carbon nanofibers, containing various metal oxide nanoparticles (e.g., Fe2O3, NiO), by the pyrolysis of metal–organic framework (MOF)‐embedded electrospun nanofibers, is reported. The resulting carbon nanofibers exhibit large mesopore volumes, contain large quantities of Faradic metal oxide nanoparticles, and are highly graphitized. The fibers also have excellent mechanical flexibility, provide fast ion transfer characteristics, and a large pseudocapacitance combined with excellent electrical conductivity, leading to large specific capacitances. Consequently, asymmetric flexible hybrid supercapacitors assembled from Fe2O3‐embedded highly graphitized carbon nanofibers (FOCNF) and NiO‐embedded highly graphitized carbon nanofibers (NOCNF) exhibit a high energy density of 43.1 Wh kg−1 at a power density of 412.5 W kg−1 and possess excellent flexibility (capacitance retention of 94.4% at 180° bending and 96.2% at 30° twisting) with superior cycling stability. This strategy provides a new MOF‐based approach for the design and synthesis of multifunctional flexible carbonaceous materials and might lead to their further application in flexible energy storage devices.

Constructing Synergistic Zn‐N4 and Fe‐N4O Dual‐Sites from the COF@MOF Derived Hollow Carbon for Oxygen Reduction Reaction

Abstract: Dual‐metal atom catalysts have been demonstrated to display higher catalytic activity and selectivity than that of solo metal atom catalysts toward oxygen reduction reaction (ORR). However, it is difficult to construct synergistic sites between different atoms even though they are immobilized in the same support, because their low‐density distribution resulted in the long distance between each other. Herein, a synergistic bimetal atomic electrocatalyst for ORR, which has highly dense Zn‐N4 (12.2 wt.% for Zn) and Fe‐N4O sites, from a core–shell hybrid of a covalent organic framework (COF) and a metal–organic framework (MOF) is demonstrated. The resultant catalyst displays a high activity for ORR with a half‐wave potential of 0.89 V vs reversible hydrogen electrode (RHE) in 0.1 m KOH, which is 50 mV more positive than that of Pt/C. The operando ANES confirms both Zn and Fe sites in the catalyst as active centers, and demonstrates that Fe sites have higher activity in the ORR process. Density functional theory (DFT) calculations further confirm the synergistic effect enables to improve the activity for both Fe sites and Zn sites in ORR. This work provides a new insight to develop ORR catalysts from COFs and MOFs.

Recent Advances on Single‐Atom Catalysts for CO2 Reduction

Abstract: Continuous consumption of fossil energy and excessive CO2 emission severely restrict human society. Sustainable carbon cycle is a promising technology to simultaneously relieve greenhouse effect and energy crisis based on electrocatalysis and photocatalysis. However, the energy conversion efficiency is confined by the poor carriers utilization and insufficient reactive sites. Single‐atom catalysts (SACs) display outstanding performance in effectively overcoming the aforementioned problems. Herein, recent advances of SACs for enhancing the efficiency, selectivity, and long‐range stability of CO2 reduction are provided. First, the characteristics of SACs have been introduced in detail to provide rational design for SACs based on the relationship between structure and performance, including type, structure, and synthesis of SACs. Then, the high performance of SACs in electrocatalytic, photocatalytic, and thermocatalytic CO2 reduction has been discussed for disclosing reaction mechanism, such as charge transfer, activation barriers, and reaction pathway. In particular, the strategies of enhancing CO2 reduction performance have been summarized to provide deep insight into designing and developing more efficient SACs. Finally, an outlook on the current challenges and perspectives of SACs for electrocatalytic, photocatalytic, and thermocatalytic CO2 reduction is proposed. This review aims to provide a systematic reference for developing SACs in advanced CO2 catalytic conversion.

In Situ/Operando Raman Techniques in Lithium–Sulfur Batteries

Abstract: Tremendous efforts have been made to fulfill the promises of lithium–sulfur (Li–S) battery as the candidate for next‐generation energy storage devices. However, challenges such as capacity degradation and dendrite growth still remain, hampering the commercialization of Li–S batteries. Different from the conventional ion‐insertion‐based lithium battery, the electrochemical and chemical processes in the cathode of Li–S battery are based on extremely complex conversion reactions. Together with the uncontrollable hostless lithium deposition process on the anode side, the future development of Li–S batteries faces great difficulty and requires deeper understanding of the fundamental mechanism. Herein, the recent applications of in situ/operando Raman techniques for monitoring the real‐time variations in Li–S batteries are summarized to reveal the reaction mechanism and guide the design of strategies for improving the battery performances. The design concepts and advantages of in situ/operando Raman studies are highlighted, and the future explorations based on such technique are discussed, aiming to accelerate the development progress of Li–S battery for practical applications.

Recent Advances in 2D Heterostructures as Advanced Electrode Materials for Potassium‐Ion Batteries

Abstract: Owing to the cost‐effectiveness, Earth abundance, and suitable redox potential, potassium‐ion batteries (PIBs) stand out as one of the best candidates for large‐scale energy storage systems. However, the large radius of K+ and the unsatisfied specific capacity are the main challenges for their commercial applications. To address these challenges, constructing heterostructures by selecting and integrating 2D materials as host and other materials as guest are proposed as an emerging strategy to obtain electrode materials with high capacity and long lifespan, thus improving the energy storage capability of PIBs. Recently, numerous studies are devoted to developing 2D‐based heterostructures as electrode materials for PIBs, and significant progress is achieved. However, there is a lack of a review article for systematically summarizing the recent advances and profoundly understanding the relationship between heterostructure electrodes and their performance. In this sense, it is essential to outline the promising advanced features, to summarize the electrochemical properties and performances, and to discuss future research focuses about 2D‐based heterostructures in PIBs.

Transition‐Metal‐Based Cocatalysts for Photocatalytic Water Splitting

Abstract: Recently, semiconductor‐based photocatalytic water splitting has been extensively studied as a promising strategy for converting solar energy into carbon‐neutral and clean H2 fuel. However, the lack of sufficient active sites for surface redox reactions generally results in unsatisfactory photocatalytic water splitting performances over semiconductors. For this problem, cocatalyst provides an encouraging solution and is of great significance in improving photocatalytic performance. Noble metals and their derivatives are mostly utilized as efficient cocatalytic components, but their scarcity and expensiveness severely hamper large‐scale applications. Thereby, the utilization of noble‐metal‐free cocatalysts has aroused immense research attention. Owing to the facile availability, low cost, large abundance, high stability, and efficient performance, transition‐metal‐based materials have been developed as desirable candidates in the photocatalytic water splitting water splitting process. This review gives an outline of some recent advances in the active transition‐metal‐based water splitting cocatalysts. First, the fundamentals of transition‐metal‐based cocatalysts are presented, including the classification, function mechanisms, loading methods, modification strategies, and design considerations. Second, the various cases of depositing reduction cocatalysts, oxidation cocatalysts, and reduction–oxidation dual cocatalysts for water splitting are further discussed. Finally, the crucial challenges and possible research directions of transition‐metal‐based cocatalysts for photocatalytic water splitting are proposed.

“Three‐in‐One” Strategy that Ensures V2O5·nH2O with Superior Zn2+ Storage by Simultaneous Protonated Polyaniline Intercalation and Encapsulation

Abstract: The structural engineering of vanadium oxides is considered as a research hotspot for enhancing their electrochemical performances applied to aqueous zinc‐ion batteries (AZIBs). In regard to the laggard Zn2+ transfer kinetic and fragile structure of V2O5·nH2O, herein, a feasible “three‐in‐one” strategy is adopted to design the structural engineering of V2O5·nH2O nanobelts through simultaneous protonated polyaniline intercalation and encapsulation (denoted as P‐VOH@P) to boost their Zn2+ storage. First, the enlarged interlayer pillared by polyaniline accelerates Zn2+ transfer speed and weakens electrostatic attraction between negative [VO] units and positive Zn2+. Second, polyaniline shell directly stabilizes the P‐VOH@P heterostructure. Third, the composition of protonated polyaniline not only improves the conductivity, but also contributes partial capacity though the reversible intrachain electronic migration. As expected, the Zn//P‐VOH@P cell exhibits specific capacities of 387 mAh g−1 with low‐mass‐loading cathode (2 mg cm−2) and 345 mAh g−1 with high‐mass‐loading cathode (5 mg cm−2) in coin cells and 360 mAh g−1 in pouch cells at 0.1 A g−1. Furthermore, the Zn//P‐VOH@P cell shows low capacity decay and good rate property. Herein, light is shed on a new strategy of engineering the vanadium oxide structure for postgeneration cathode material and paves a novel way to the advanced energy‐storage system.

Nanoscale Design of Pd‐Based Electrocatalysts for Oxygen Reduction Reaction Enhancement in Alkaline Media

Abstract: Palladium (Pd)-based electrocatalysts have recently emerged as one class of the foremost promising candidates for the oxygen reduction reaction (ORR) in alkaline media due to their excellent ORR activity and durability and lower costs compared with platinum. Insightful design of Pd-based nano-architectures with optimized active surface sites and maximal intrinsic performance is central to promoting the ORR applications. To further accelerate the sluggish ORR kinetics at the cathode of fuel cells and substantially decrease the overall cost of the electrocatalysts, various strategies, including controlled sizes and shapes with selected crystallographic facets, crystal-phase engineering, heteroatom doping, tailored surface strains, and surface engineering by de-alloying, have been extensively developed in the past decade. In this review, a brief introduction to the fundamental ORR mechanisms of Pd-based electrocatalysts in alkaline media is presented, followed by a thorough discussion on various strategies for delicately designing high-performance Pd-based catalysts with corresponding examples. Thereafter, the perspectives and new insights into the challenges are outlined, and some emerging research directions related to the rational design and controlled synthesis of Pd-based ORR electrocatalysts are also proposed.

Atomic‐Level Metal Electrodeposition: Synthetic Strategies, Applications, and Catalytic Mechanism in Electrochemical Energy Conversion

Abstract: Electrochemical energy conversion is considered a promising method to alleviate the global energy crisis and environmental issues. By decreasing the length scale to the atomic level, the energy-related metal electrocatalysts can possess unique catalytic properties, which can maximize their utilization. The electrodeposition technique has gained unprecedented attention for the synthesis of atomic-level metal catalysts. In this review, the recent progress on the various strategies used to electrodeposit atomic-level metal catalysts is summarized. The basic principles of the surface-limited electrochemical techniques (underpotential deposition (UPD)) and their applications in the self-terminating growth of atomic-level metal catalysts are highlighted. This review also discusses the mechanistic investigations, comprehensive understanding of the structure–activity relationships at the atomic level and the application of these atomic-level catalysts in the electrochemical energy conversion in details. Finally, the current challenges and future directions on the potential use of the atomic level electrodeposition are presented.

Advances in Prostate‐Specific Membrane Antigen (PSMA)‐Targeted Phototheranostics of Prostate Cancer

Abstract: With the advent of the era of precision medicine, prostate‐specific membrane antigen (PSMA)‐targeted theranostic strategies have had a profound impact on prostate cancer research. As a specific membrane antigen target, PSMA is not only widely expressed in prostate cancer tissues but its expression is also correlated with tumor aggressiveness. Because of the noninvasiveness, real‐time nature, high sensitivity, and low side effects of phototheranostics, in recent years, there has been a rapid advancement in PSMA‐targeted phototheranostics, such as near‐infrared fluorescence imaging and imaging‐guided surgical navigation, photoacoustic imaging, dual‐modality hybrid imaging and imaging‐guided surgical navigation, photodynamic therapy, and photothermal therapy. Herein, the design and application of various types of imaging probes and photosensitizers based on PSMA targeting developed in the past two decades are reviewed, with a focus on molecular design strategies for near‐infrared fluorescent probes and hybrid tracers. In addition, the challenges of and future opportunities for the clinical translation of phototheranostics in the field of prostate cancer are discussed.

Recent Progress in Thermal Conversion of CO2 via Single‐Atom Site Catalysis

Abstract: CO2 emission has been an international issue of great concern. Utilizing of CO2, especially converting it to value‐added products, is widely investigated, among which the thermal conversion of CO2 has enormous potential for industry. Researches on single‐atom site catalysis (SAC) have become increasingly systematic during the last years. High performance and distinctive selectivity that SAC exhibits attribute to the isolated structure a large extent. To understand the structure–performance relationship of SAC in CO2 activation, issues including substrate, active components, coordination, chemical structure, etc. are of the essence not only in academia but also in industry. However, it is far away from the vision that the synthetic procedure and reaction pathway are deeply comprehended, thereupon precise single‐atom sites with specific structure are constructed and elementary reactions are regulated at will. Still a lot of efforts are needed to this field. Herein, CO2 reduction reactions are reviewed according to the products, and then catalysts are introduced by the substrate. The promoter, stability, synthesis/regeneration, characterization, and theory calculation issue related to SAC and CO2 activation are comprehensively summarized and discussed. Looking back the progress, challenge and outlook of single‐atom site catalysis are also proposed.

The Origin of Fast Lithium‐Ion Transport in the Inorganic Solid Electrolyte Interphase on Lithium Metal Anodes

Abstract: Solid electrolyte interphase (SEI) plays an indispensable role in stabilizing lithium metal batteries (LMBs). An ideal SEI is supposed to impede the electrolyte degradation on lithium metal anodes while allowing lithium‐ion transport. However, the ionic transport mechanism in SEI is not fully understood. Herein, first‐principles calculations are performed to probe the ionic transport mechanism in inorganic SEI and the role of carrier concentration is highlighted. The low ionic conductivity in bulk inorganic SEI (Li2O, LiOH, Li2CO3, and LiF) is ascribed to its low carrier concentration. The Li2O/LiF interface delivers both a high carrier concentration and ionic conductivity despite an indifferent diffusion barrier. Herein, not only the lithium‐ion transport mechanism in inorganic SEI is unveiled but also the general references for the rational design of high‐ionic‐conductivity SEI on working Li‐metal anodes are afforded.

Carbon Dots for Intracellular Sensing

Abstract: Carbon dots (CDs), a type of small, carbon element‐based nanomaterials, have found numerous applications in many fields due to their outstanding properties like fascinating photoluminescence characteristic, great biocompatibility, easy and economical synthesis, and facile functionalization. Over the last decade, huge progress and achievements have been made in terms of the applications of CDs in cellular detection. However, a comprehensive review focusing on this topic is still lacking. Herein, the recent progress in CDs‐mediated intracellular detection, including the fluorescence imaging of cellular structures (e.g., nucleus/nucleolus, mitochondrion, lysosome, endoplasmic reticulum, Golgi apparatus, and lipid droplet), the fluorescence detection of a large variety of cellular substances (including endogenous biomacromolecules and their monomers, vitamins, important metabolites, adenosine triphosphate, reactive oxygen species, biothiols, ions, and exogenous compounds), and the monitoring of cellular parameters (pH, temperature, and mitochondrial membrane potential), is thoroughly reviewed. The synthesis, functionalization, and performance of the CDs that serve as fluorescent nanoprobes in living cells are presented. Their underlying working mechanisms are also discussed if available. Finally, the challenges and future research directions of the related research field are listed. This review may foster the future development of more CDs with better cellular sensing performance.

Facile Synthesis of Fe‐Doped CoO Nanotubes as High‐Efficient Electrocatalysts for Oxygen Evolution Reaction

Abstract: Developing high‐performance, low‐cost, and robust electrocatalysts is of great importance to boost the efficiency of oxygen evolution reaction (OER). Herein, based on the integrated design of chemical composition and geometric structure, Fe‐doped CoO nanotubes (NTs) with high OER activity are prepared by a facile template‐free approach. The construction of this tubular structure is realized via a simple wet‐chemical reaction to prepare solid nanorods as precursor and a subsequent calcination treatment of the precursor to form hollow cavity. The favorable composition and unique hollow structure endow these Fe‐doped CoO NTs with remarkable activity toward OER. When used as the electrocatalyst for OER, the Fe‐doped CoO NTs show a small overpotential of 282 mV at the current density of 10 mA cm−2, a low Tafel slope of 78.26 mV dec−1, and a high turnover frequency of 0.0965 s−1 at the overpotential of 282 mV, which is superior to those of CoO NTs and solid CoO nanoparticles. Moreover, the Fe‐doped CoO NTs also exhibit excellent long‐term stability of 24 h at the current density of 10 mA cm−2.

Bifunctional Catalyst for Liquid–Solid Redox Conversion in Room‐Temperature Sodium–Sulfur Batteries

Abstract: Room‐temperature sodium–sulfur (RT Na–S) batteries are one of the most promising large‐scale energy storage systems due to their high energy density and abundant Na reserve. However, the main challenges of poor rate performance and unsatisfactory capacity ascribing to sluggish conversion reaction kinetics and severe shuttling effect of long‐chain sodium polysulfides (NaPSs) retard the practical application. An ideal RT Na–S cathode host should concurrently incorporate strong adsorption capability and high catalytic activity. Herein, a bifunctional catalyst is designed, i.e., cobalt sulfide–selenide heterostructure in multichannel carbon nanofibers (denoted as CoS2–CoSe2@CNFs), as sulfur host for RT Na–S batteries. This unique catalyst combines the advantages of CoS2 with high adsorption capability toward soluble sodium polysulfides and CoSe2 with efficient catalytic activity to promote the liquid–solid conversion process. As a result, the S/CoS2–CoSe2@CNFs cathode achieves a high initial capacity (1295 mAh g−1 at 0.1 A g−1), long cycling stability (749 mAh g−1 after 200 cycles at 1 A g−1), and outstanding rate capability (866 mAh g−1 at 3 A g−1). This work demonstrates a new bifunctional design strategy from theoretical and experimental aspects for high‐performance RT Na–S batteries.

Surface Reconstruction of Ni‐Rich Layered Cathodes: In Situ Doping versus Ex Situ Doping

Abstract: The structural instability and sluggish Li+ diffusion kinetic of the nickel‐rich LiNixCoyMn1−x−yO2 (NCM) cathode still hinder its further commercialization for lithium‐ion batteries. Doping heteroatoms are widely studied as an effective strategy to maintain structural and thermal stability for improving the capacity retention of NCM during cycling. Herein this work, in situ Zn2+‐doped NCM (in situ Zn‐NCM) is successfully designed by atomic layer deposition (ALD) combined with annealing. In comparison to ex situ Zn2+‐doped NCM (ex situ Zn‐NCM), in situ Zn‐NCM can better enhance the layered structure stability and reduce the generation of surface defects due to that it has lower migration energy barrier and more uniform distribution of heteroatoms. As a result, at a high cutoff voltage of 4.5 V, in situ Zn‐NCM with the obvious advantages of lower cation mixing, better phase transition stability, as well as more efficient charge transfer displays higher reversible capacity (i.e., 203.2 mAh g−1 at 50 mA g−1) and initial Coulombic efficiency (85%) compared to ex situ Zn‐NCM and the pristine NCM. Therefore, in situ doping is a novel and universal strategy to enhance battery performance of high‐energy‐density NCM cathodes for lithium‐ion batteries.

Postsynthetic Modification of Metal−Organic Frameworks for Photocatalytic Applications

Abstract: Metal−organic frameworks (MOFs) are a new class of porous, crystalline materials with promising applications in the fields of energy and environment. Postsynthetic modification (PSM) approaches are shown to be powerful techniques to introduce new functionalities to parent frameworks. PSM methods to functionalize MOFs can be divided into four main categories based on their unique structures: covalent modification, coordinative transformation, encapsulation, and hybridization with other compounds. These approaches are proven to be an important tool for increasing structural stability and introducing desired properties, which expand the applications of MOFs. This review focuses on the current advancements of four PSM methods to construct functionalized MOFs for photocatalytic applications in water splitting, CO2 reduction, organic transformation, and degradation of water pollutants. The challenge and perspectives on PSM of MOFs for photocatalysis are also discussed.

ZnIn2S4‐Based Nanostructures in Artificial Photosynthesis: Insights into Photocatalytic Reduction toward Sustainable Energy Production

Abstract: As one of the most attractive technologies, photocatalysis arouses tremendous interest to directly harvest, convert, and store renewable solar energy for solving the energy crisis. Zinc indium sulfide (ZnIn2S4), a novel ternary metal chalcogenide, is highly desired owing to its non‐toxicity, low cost, and easy fabrication. However, it still suffers from some problems, including low charge‐carrier transfer rate and the ultrafast electron–hole recombination. Hence, various efficient modification methods are developed for enhancing the photocatalytic performance of ZnIn2S4 nanomaterials. Herein, the photocatalytic energy applications of ZnIn2S4‐based nanocomposites are systematically summarized, followed by a thorough discussion on the synthesis methods of ZnIn2S4 micro/nanostructures. Furthermore, special attention is paid to various design strategies, including dimensionality tuning, element doping, vacancy control, cocatalyst loading, and heterojunction construction. Many important energy conversion applications are also addressed, such as photocatalytic water splitting, carbon dioxide reduction, and nitrogen fixation. The influence of physicochemical properties, including structure, optical, electronic, and adsorption, on the charge dynamics for boosted photocatalytic energy applications are concluded to unravel the property–application relationship. Through reviewing the significant state‐of‐the‐art advances on this topic, the current challenges and the crucial issues of ZnIn2S4‐based photocatalysts are prospected.

Recent Progress in Ionic Liquids for Stability Engineering of Perovskite Solar Cells

Abstract: Perovskite solar cells attract widespread attention due to their impressive power conversion efficiencies, high absorption coefficients, tunable bandgap, and straightforward manufacturing protocols. However, in the process of further development and optimization toward mass production, the long‐term stability stands as one of the most urgent challenges that need to be overcome. Given the excellent thermal stability and high structural designability, ionic liquids (ILs) are relatively green room‐temperature molten salts that have been widely applied to perovskite photovoltaic devices with promising results in view of improved stability and enhanced device performance. In this review, the reasons and mechanisms of instability of such devices under external and internal factors are analyzed. The current strategies of ILs engineering for improved stability of the devices are classified and summarized, including the IL‐assisted perovskite film evolution and IL‐modified photophysical properties of the perovskite photoactive layer and the related stability and photovoltaic performance of the devices. The challenges that stand as obstacles toward further development of perovskite solar cells based on IL engineering and their prospects are also discussed.

Conductive 2D Conjugated Metal–Organic Framework Thin Films: Synthesis and Functions for (Opto‐)electronics

Abstract: Two‐dimensional conjugated metal–organic frameworks (2D c‐MOFs), possessing extended π–d conjugated planar structure, are emerging as a unique class of electronic materials due to their intrinsic electrical conductivities. Taking advantage of the large‐area flat surface, 2D c‐MOF thin films allow facile device integration with sufficient electrode contact, high device stability, and high charge transport, thereby emerging as appealing active layers for a broad range of electronic applications. Synthesis and device investigation of thin films are of great importance for their further development, which are systematically summarized in the current review. Here, the authors firstly introduce the molecular structures of representative 2D c‐MOFs and present the fundamental understanding on structure–property relationships. After that, the state‐of‐art synthetic methodologies toward high‐quality 2D c‐MOF thin films are summarized, including exfoliation and reassembly (ERA), liquid‐interface‐assisted synthesis (LIAS), and chemical vapor deposition (CVD). By considering the advantages of 2D c‐MOF films in device integration, remarkable progress in (opto‐)electronic device applications are discussed, such as field‐effect transistors (FETs), chemiresistive sensors, photodetectors, superconductors, and thermoelectrics. In the end, the remained challenges about the development of 2D c‐MOF films for (opto‐)electronics are highlighted and possible future directions are proposed to address these challenges.

Spacer Organic Cation Engineering for Quasi‐2D Metal Halide Perovskites and the Optoelectronic Application

Abstract: Recently, organic and inorganic halide perovskites are one of the most popular semiconductors owing to their enormous potential for optoelectronic application, such as photovoltaics (PV), light‐emitting diode (LED), photodetector, and so on. The photoelectric conversion efficiency of 3D organic–inorganic hybrid perovskite solar cells has increased rapidly; however, the commercialization of the related devices is largely hampered by the poor stability of perovskite materials under environmental stress. Compared to 3D halide perovskites, quasi‐2D (Q‐2D) perovskites have improved moisture stability and less tendency for ion migration, which offers a new approach to stabilize perovskite‐based optoelectronic devices. Furthermore, Q‐2D hybrid perovskites have diverse structures with different quantum confinement and dielectric confinement characteristics, which enables the fine‐tuning of their optoelectronic properties through structure engineering. Depending on the different structures of spacer organic cations, the Q‐2D perovskite structure mainly includes Ruddlesden−Popper (RP) phase structure, Dion−Jacobson (DJ) phase structure, and alternating cation in the interlayer space (ACI) phase structure. In this review, the state‐of‐the‐art in Q‐2D perovskites is discussed based on their structural engineering, and an overview of PV and LEDs applications is provided. Finally, a brief outlook with respect to the development of Q‐2D perovskite materials, as well as advanced device, is provided.

Trace Solvent Additives Enhance Charge Generation in Layer‐by‐Layer Coated Organic Solar Cells

Abstract: In bulk heterojunction (BHJ) organic solar cells (OSC), the photoactive layer morphology controls charge carrier generation, transport, and extraction. Obtaining the “optimum” morphology is often achieved by empiric optimization of processing conditions and post‐processing treatment. Better control over the morphology can be achieved by sequential photoactive layer‐by‐layer (LbL) deposition techniques, creating a pseudo‐bilayer OSC. Solvent additives can be used to modify the vertical component distribution, thereby enhancing OSC efficiency. However, the impact of solvent additives on device photophysics is often unclear. Here, the photophysics of LbL‐coated PM6/Y6 organic solar cells are reported. Enhanced power conversion efficiencies (PCEs) are observed when using 1‐chloronaphthalene (CN) as a solvent additive. Transient absorption (TA) spectroscopy indicates that the addition of 0.5% CN facilitates both exciton dissociation and charge separation, while excessive (>1%) use of CN causes fast geminate and non‐geminate charge recombination and consequently deteriorates device performance. The results outline routes to fine‐tune the morphology of LbL‐coated photoactive layers of OSCs and provide insight into the reasons for increased PCEs.

Flexible and Robust Ti3C2T x /(ANF@FeNi) Composite Films with Outstanding Electromagnetic Interference Shielding and Electrothermal Conversion Performances

Abstract: Flexible and robust multifunctional electromagnetic interference (EMI) shielding materials are playing an increasingly important role in areas of aerospace, electronic communication, artificial intelligence, and wearable electronic devices. Herein, the magnetic and conductive Ti3C2T x /(ANF@FeNi) EMI shielding composite films are fabricated via in situ growth and vacuum‐assisted filtration methods. The introduction of magnetic FeNi nanoparticles can effectively enhance the electromagnetic recombination losses, leading to improved EMI shielding effectiveness (EMI SE) of the composite films. The obtained Ti3C2T x /(ANF@FeNi) composite films show excellent EMI shielding and electrothermal conversion performances. When the mass fraction of Ti3C2T x and FeNi fillers is 60 wt% and their mass ratio is 4:1, the EMI SE of the composite films (50 μm) reaches 60.7 dB in the X‐band (8.2–12.4 GHz). When a low voltage of 3 V is applied, the surface heating temperature of the composite films quickly reaches 111.2 °C. Moreover, the composite films possess satisfied long‐term heating stability under the constant applied voltage. In addition, the composite films exhibit excellent thermal conductivity and mechanical properties. The thermal conductivity (λ) and thermal diffusivity (α) reach 4.72 W m−1 K−1 and 4.36 mm2 s−1, respectively, and the tensile strength and tensile modulus reach 113.4 MPa and 3.1 GPa, respectively.

Modified Metal−Organic Frameworks for Electrochemical Applications

Abstract: Metal−organic frameworks (MOFs) are neo‐type porous materials synthesized via organic ligands and metal ions, which have drawn much attention due to their unparalleled advantages such as high specific surface area, large and clear pore structures, and uniformly distributed active sites. In these years, modified MOFs are regarded as kinds of materials with excellent electrochemical properties, that overcome poor conductivity and stability of original MOFs and narrow the gap between the basic science of MOFs and their future applications. At the same time, it also provides an opportunity to elaborate the synergistic effect of the synthesis strategy of modified MOFs on the performance. This review focuses on the synthesis, structure characterization, and electrochemical adhibition of modified MOFs and discusses the challenges and application prospects of modified MOFs in energy storage and conversion.

Emerging Ultrahigh‐Density Single‐Atom Catalysts for Versatile Heterogeneous Catalysis Applications: Redefinition, Recent Progress, and Challenges

Abstract: In recent years, single‐atom catalysts (SACs) with high metal loading have emerged in different heterogeneous catalysis fields and shown extraordinary catalytic properties. When there are enough coordination atoms (or functional groups) on the supports, it is possible to achieve a limit monolayer atom loading on the surface of supports with ultrahigh atom density (5–15 atoms nm−2) and extremely close site distance (0.2–0.5 nm), by using appropriate synthesis methods and procedures. These high‐density metal atoms usually have no or less metal bonds, which are mostly isolated by support atoms to form 3D foam‐like atomic constructions. Herein, a new notion of metal atomic foam catalysts (AFCs) is propsed to redefine these ultrahigh‐density SACs accommodated by specific supports. This new paradigm of 3D atomic construction for SACs has potential significance for both theoretical research and industrial applications. The latest major advancements in the controllable synthesis of AFCs on various supports (e.g., polymer, carbon, and metallic compound) via different methods (bottom‐up or top‐down approaches) are summarized. The latent catalytic principles and typical application cases of AFCs are emphasized in a wide range of heterogeneous catalysis fields (e.g., thermocatalysis, photocatalysis, electrocatalysis, etc.). The challenges and prospects of this newly 3D ultrahigh‐density AFCs materials in practical industrial application are pointed out as well.

Rhodium–Cobalt Alloy Nanotubes Toward Methanol Oxidation Reaction

Abstract: The sluggish reaction kinetics of the anodic methanol oxidation reaction (MOR) seriously hinders the commercial development of direct methanol fuel cells. Considering the vital role of catalysts, this work focuses on the synthesis of rhodium–cobalt alloy nanotubes (RhCo‐NTs) through a simple one‐pot reduction approach using hydrazine hydrate as a reducing agent. RhCo‐NTs with different Rh/Co atomic ratios can be handily achieved by simply controlling RhIII/CoII feeding proportions. The hollow and tubular architecture of RhCo‐NTs gains abundant boundary/defect atoms, improves the atomic utilization of Rh, and enlarges the valid connection between active sites and reactants. Compared with commercial Rh nanocrystals, RhCo‐NTs with optimized Rh/Co atomic ratio show sharply enhanced MOR electroactivity and long‐term stability because of the particular tubular morphology, big electrochemical active area, suitable Co introduction, excellent self‐stability, and eminent anti‐poison capability.