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A novel sheet-like tin-based metal–organic framework exhibited a specific capacity for lithium storage as high as 1033.3 mAh g−1 at 200 mA g−1 with excellent cycling stability. This framework, due to its unique porous structure and multiple lithium storage sites, could better cope with challenges occurring during lithium insertion/extraction than could traditional tin materials. [ABSTRACT FROM AUTHOR]

This study introduces a versatile electrolyte additive, nicotinamide, for zinc anodes, aiming to facilitate uniform deposition and suppress water-induced side reactions. The molecular structure, consisting of a pyridine ring and an amide function group, endows NTA molecules with the ability to regulate electrolyte pH, enhance nucleation overpotential, and constrain 2D diffusion of Zn2+. As a result, the full battery configuration with this additive achieved an impressive lifespan of over 10 000 cycles. [ABSTRACT FROM AUTHOR]

The environment-friendly electrochemical nitrogen reduction reaction (NRR) is considered to be a promising alternative to the traditional Haber–Bosch process for ammonia production. However, the stability of nitrogen and competitive hydrogen evolution reaction (HER) lead to low faradaic efficiency (FE) and ammonia selectivity for the NRR. Compared with the NRR, the electrochemical nitrate reduction reaction (NO3RR), with no process of N2 adsorption, exhibits a higher NH3 yield and FE. In this work, the MIL-101(Fe) is synthesized and composited with Nb2C MXene, which exhibited excellent NRR and NO3RR performance. For the NRR, the MIL-101(Fe)@Nb2C achieved an ammonia yield of 8.92 μg h−1 cm−2 and a high FE of 20.77%. Meanwhile, for the NO3RR, it achieved a large NH3 yield of 199.68 μg h−1 cm−2 and a high FE of 89.9%. In addition, MIL-101(Fe)@Nb2C exhibits excellent stability for the NRR and NO3RR. DFT calculations proved that the interfacial interaction between Nb2C and MIL-101(Fe) acquired a significant synergistic mechanism to improve the catalytic performance. Since the NH3 yield and FE of the NO3RR are much higher than those of the NRR, it is vital to design NRR catalysts that can easily adsorb and activate nitrogen as well as inhibit the HER. [ABSTRACT FROM AUTHOR]

The purification of carbon monoxide in H2-rich streams is an urgent problem for the practical application of fuel cells, and requires the development of efficient and economical catalysts for the preferential oxidation of CO (CO-PROX). In the present work, a facile solid phase synthesis method followed by an impregnation method were adopted to prepare a ternary CuCoMnOx spinel oxide, which shows superior catalytic performance with CO conversion of 90% for photothermal CO-PROX at 250 mW cm−2. The dopant of copper species leads to the incorporation of Cu ions into the CoMnOx spinel lattice forming a ternary CuCoMnOx spinel oxide. The appropriate calcination temperature (300 °C) contributes to the generation of abundant oxygen vacancies and strong synergetic Cu–Co–Mn interactions, which are conducive to the mobility of oxygen species to participate in CO oxidation reactions. On the other hand, the highest photocurrent response of CuCoMnOx-300 also promotes the photo-oxidation activity of CO due to the high carrier concentration and efficient carrier separation. In addition, the in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) confirmed that doping copper species could enhance the CO adsorption capacity of the catalyst due to the generation of Cu+ species, which significantly increased the CO oxidation activity of the CuCoMnOx spinel oxide. The present work provides a promising and eco-friendly solution to remove the trace CO in H2-rich gas over CuCoMnOx ternary spinel oxide with solar light as the only energy source. [ABSTRACT FROM AUTHOR]

SnO2, the most promising alternative to TiO2 as the electron transport layer (ETL), has attracted great attention for perovskite solar cells (PSCs) due to its high bulk electron mobility, good band energy at the ETL/perovskite interface, and high chemical stability. To enable more efficient carrier transfer and extraction, elemental doping with different metal cations has been studied in SnO2 ETLs. However, the systematic investigation of the doping mechanism lag far behind their efficiency promotion. In this paper, elements of the same main group (Li, Na, K) and period (K, Ca, Ga) have been selected for doping in SnO2. The results showed that among the properties of the dopants, the electronegativity has the greatest influence. The smaller the electronegativity of the doping species, the more conducive it is to carrier transmission and separation. The corresponding mechanism was proposed and discussed. At last, an efficiency of 20.92% of PSCs based on SnO2–K was achieved. In addition, the doped SnO2 is more beneficial for the growth of perovskite crystals, thus reducing grain boundaries and enhancing the stability of the device. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) have been rapidly developed as an effective replacement or supplement for lithium-ion batteries (LIBs) due to the high natural abundance and low cost of sodium resources. Sodium super ion conductor (NASICON)-type materials have high ionic conductivity and excellent structural stability, making them one of the potential electrode candidates for SIBs. V(vanadium)-based polyanionic compounds have been the most extensively studied NASICON-structure materials. However, the environmental pollution and high-cost issues of V-based materials demand serious consideration. Currently, V-free NASICON-type electrodes have garnered a lot of attention. In this review, V-free NASICON electrodes for SIBs are first systematically summarized. The latest advances in related cathode/anode materials with various metal redox couples are classified and introduced in terms of their preparation method, structural characteristics, and electrochemical performance. Moreover, the performance improvement strategies and future prospects are discussed. It is expected that the insights may inspire future research into the development of more clean, efficient, and low-cost electrodes for SIBs. [ABSTRACT FROM AUTHOR]

The elimination of electron transport layers (ETLs) to fabricate ETL-free perovskite solar cells (PSCs) could save manufacturing costs and time. However, compared with PSCs based on the traditional architecture, ETL-free PSCs suffered low efficiency due to the device shunting and large energy barriers for carriers. Herein, a bifunctional interfacial modification material, 3-aminopropyl trimethoxy silane (APS), is selected and in situ grown on a transparent conducting oxide (TCO). On the one hand, the increased hydrophobicity of APS modified indium tin oxide (ITO) could improve the crystal growth of perovskites, resulting in larger grain sizes and reduced surface defects. On the other hand, the APS modification could improve the energy level alignment of ITO and the perovskite, leading to enhanced electron extraction and hole blocking. The PCE of the ETL-free PSCs based on APS modified ITO reached 19.09%, which was over 60% higher than that of ETL-free PSCs based on ITO. [ABSTRACT FROM AUTHOR]

The elimination of the electron transport layer (ETL) to fabricate ETL-free perovskite solar cells (PSCs) could save manufacturing cost and time. However, the direct contact of the perovskite and transparent conducting oxide (TCO) electrodes results in mismatched energy level alignment and current leakage. Therefore, ETL-free PSCs suffer from unsatisfactory photovoltaic performance. Herein, a special perovskite material with a cascaded band gap, called gradient homojunction perovskite (GHJP), is designed and synthesized by a large cation-assisted method. The inherent nature of GHJP was the type-II cascaded energy level alignment, which could block holes during the electron collection. This facilitated the dissociation of the excitons in the GHJP. Due to the excellent properties, ETL-free PSCs based on GHJP obtained 20.55% PCE, which was over 90% higher than that of ETL-free PSCs based on the control perovskite material. [ABSTRACT FROM AUTHOR]

The large-scale application of clean electrochemical energy storage and conversion systems such as water-splitting devices and Zn–air batteries greatly depends on the development of low-cost and highly efficient electrocatalysts. Transitional metal sulfides (TMSs) have gained great research interest owing to their high intrinsic catalytic activity, adjustable electronic structures, and various crystal structures and phases. Meanwhile, metal–organic frameworks (MOFs) are ideal precursors for the preparation of TMSs due to the diverse metal nodes, organic ligands, topologies, and morphologies of MOFs. In addition, MOFs could act as hosts for the incorporation of guest molecules, which could further expand the metal types of TMSs. In this review, the recent progress of MOF-derived TMS electrocatalysts for hydrogen evolution reactions (HERs), oxygen evolution reactions (OERs) and oxygen reduction reactions (ORRs) are summarized. After a brief introduction to the reaction mechanisms, the preparation strategies, structures, catalytic performances, and catalytic mechanisms of the TMSs are discussed to give readers a comprehensive understanding of this prosperous field. The strategies such as nanostructure engineering, interface engineering and heteroatom doping used to improve the performance of the electrocatalysts are discussed in each section. In addition, bifunctional catalytic performances of the catalysts for overall water splitting and rechargeable Zn–air batteries are illustrated. Furthermore, challenges and opportunities for the future development of this field are proposed. We expect this review could provide guidelines for the design and fabrication of TMSs, and initiate more efforts and new discoveries in this emerging research area. [ABSTRACT FROM AUTHOR]

The rapid development of electric vehicles and consumer electronics places higher demands on the performance of secondary batteries. Tin-based materials are expected to be a commercial anode material candidate of next-generation rechargeable batteries due to their high gravimetric/volumetric capacity. However, tin anodes have large volume changes during charge–discharge cycles which leads to a rapid capacity decay. Emerging tin-based metal–organic frameworks (Sn-MOFs) have recently attracted the attention of researchers. Their characteristics of tunable porosity, huge surface areas and multiple active sites offer a wide range of possibilities for Li/Na ion storage and transport, and the coordination bonds stabilize the Sn atoms to the organic matrix buffering pulverization and aggregation. Besides, MOF-related Sn derivatives could also have novel diverse functional structures and achieve high-rate capacity and excellent cycle stability. In this review, we mainly summarize the structural features, energy storage mechanism, and recent advances in the rational design and preparation of Sn-MOFs and MOF-derived Sn-based composites for LiB and SIB anodes, and current challenges and future directions for further development are discussed. [ABSTRACT FROM AUTHOR]

Due to the low cost and strong hydrophobicity of carbon electrodes, carbon-based perovskite solar cells (C-PSCs) have drawn much attention. Copper(I) thiocyanate (CuSCN) is a favorable hole transport layer in perovskite solar cells (PSCs) because of its high chemical stability, high conductivity, and high hole mobility, but pinholes often appear during CuSCN film fabrication. In this work, organic ammonium salt, phenethylammonium iodide (PEAI), has been applied to modify the CuSCN film. The results indicated that PEAI not only eliminated the pinholes, but also passivated the perovskite film and enhanced the interfacial connection. Therefore, the power conversion efficiency (PCE) of C-PSCs increased by about 11%. The stability test showed that the C-PSCs, without any encapsulation, could maintain 70% of the initial efficiency after storage for 800 h in ambient air with 60%–70% relative humidity at room temperature. [ABSTRACT FROM AUTHOR]

Through theoretical calculation and experimental research, the electrodeposition process of preparing a copper catalyst in an acid electrolyte using polyethylene glycol (PEG), polyethylene imine (PEI), and a PEG and PEI mixture as additives was studied. The cutting-edge molecular orbital information of PEG and PEI was studied through quantum chemical calculations. Molecular dynamics simulations were performed to study the interface interaction between PEG and PEI and the metal surface. The microscopic morphology and crystal structure of the coating were characterized by scanning electron microscopy (SEM) and X-ray diffractometer (XRD). It is found that adding composite additives to the studied acidic copper electroplating could obtain a copper coating with a spherical shape, small particle size, and good dispersion effect. This study proves that a PEI and PEG-based copper plating solution is a promising method for preparing high-performance copper-based catalysts in the acid copper electroplating process. [ABSTRACT FROM AUTHOR]

The presence of organic pollutants in the world is harmful to our existence and the environment. So efficient and energy-saving methods for the degradation of organic pollutants present in the environment are important and beneficial for humans and the environment. The use of emerging photocatalytic technology using semiconductor materials to degrade organic pollutants is an effective method with potential prospects for the future. In this work, quantum chemical calculations and classical molecular dynamics simulations are employed to investigate the performances and related reactivities of sulfide semiconductor materials for the photocatalytic degradation of several common organic compounds. The reactivity of the organics is studied using quantum chemical calculations. The adsorption behaviors of several types of organic compounds on the surfaces of sulfide semiconductors in the gas phase were investigated, then similar adsorption processes in the aqueous phase were studied, and then CdS semiconductors were used to explore the influence of different crystal planes on the adsorption behavior of organic matter. Based on adsorption energy calculations, the best adsorption performance for a specific type of organic matter on a sulfide semiconductor was explored, together with an adsorption comparison in the gas and water phases. The results of this study may provide theoretical guidance for sulfide semiconductor photocatalysis technology and give ideas for subsequent experiments. [ABSTRACT FROM AUTHOR]

Two dimensional (2D) perovskite materials, are more stable than 3D perovskite materials, which could solve the stability issue of perovskite solar cells (PSCs). However, the photovoltaic conversion efficiency (PCE) of PSCs based on 2D perovskite materials was low, due to the high dielectric and quantum confinement of 2D perovskite. In this work, we propose a solvent-assisted method to prepare 2D perovskite films, where the solvent was distributed in a gradient. Therefore, the top-down crystallization process of 2D perovskite can be accurately controlled. The PCE of PSCs fabricated by the solvent-assisted method was enhanced by 48%, compared with the control device. For the packaged devices, the stability test demonstrated that 94% of the initial PCE was still maintained after 1500 hours of storage (25 °C, RH 40%). After carefully analyzing the photophysical process of the carriers in the PSCs based on 2D perovskite, the enhanced carrier transfer mechanism of the solvent-assisted method has been proposed. [ABSTRACT FROM AUTHOR]

Benefiting from the high electrochemical surface area brought by the 2D nanosheet structure, MoS2 has received great research attention for the hydrogen evolution reaction (HER). Recently, it has been demonstrated that by constructing a transitional metal sulfide–MoS2 heterostructure, the HER performance of the MoS2-based catalysts can be further improved. It is even possible to obtain bifunctional catalysts for both HER and oxygen evolution reaction (OER) due to the synergistic effect of the different components in the composite, the electronic effect to enable an efficient electron transfer and appropriate binding energy for the intermediates of the electrocatalytic reactions, and the surface defects on the interface of the heterostructures. Herein, we review the recent progress on the construction of the transitional metal sulfide–MoS2 heterostructure for water splitting based on non-self-supporting and self-supporting catalysts. The surface and interface parameters of the heterostructures are discussed in detail to reveal the key roles of the hybrid structures for energy conversion. We also pay special attention to the theoretical simulations based on first principles to clarify the relationships between the electrochemical performance and structure parameters. Finally, the prospects and challenges of the transition metal sulfide–MoS2 heterostructures for water splitting in the future are proposed to prompt the reasonable design of transition metal sulfide–MoS2 heterostructures for full water splitting. [ABSTRACT FROM AUTHOR]

Catalytic hydrogenation of CO2 to chemicals is an important approach for reducing the concentration of CO2 in the atmosphere. Among all value-added chemicals, alcohol can be considered one of the most economical products owing to its high calorific value and vast applications. There is no unanimous pathway of CO2 reduction to methanol and ethanol owing to its complex mechanism. In this work, we theoretically investigated the intermediates and pathway of the CO2RR to low-carbon alcohols using the density functional theory analysis and selected optimal reaction pathways by comprehensive evaluations. Additionally, the effects of environmental temperature and reaction phases were studied. This work can be regarded as a theoretical and introductory foundation for the further design of catalysts. [ABSTRACT FROM AUTHOR]

Silicon has received much attention due to its high theoretical capacity as the electrode of lithium-ion batteries (LIBs). However, the poor stability caused by the volume expansion problem affects the cycle life of batteries, thus severely limiting the application of the silicon anode. In the present work, we engineered silicon nanotubes with hollow-structure to accommodate the volume expansion of silicon and improve the electrochemical stability of lithium ion batteries. Hollow silicon nanotubes were in situ synthesized on carbon cloth (HSiNTs/CC) by reducing silicon oxide and corroding zinc oxide nanorod templates and directly used as the anode of lithium-ion batteries without any binders or conductive additives. The results of electrochemical measurements indicated that HSiNTs/CC exhibits superior LIB performance with excellent cycling stability and good rate capability. At a current density of 100 mA g−1, a reversible capacity of 1420 mA h g−1 was achieved and the fabricated LIB could retain 93.7% of the initial capacity after 100 cycles. Even at a decoupled current density of 1000 mA g−1, the LIB still possesses a capacity of 1026 mA h g−1 and 98.3% capacity retention after 100 cycles. The results demonstrated that the thin hollow structures were well suited to accommodate the volume expansion of silicon and improve the stability of the HSiNTs/CC anode during the lithiation–delithiation cycles, which shines some light on the reasonable design and preparation of silicon anodes for ultra-stable lithium-ion batteries. [ABSTRACT FROM AUTHOR]

As a promising and important carbon source, utilization of carbon dioxide (CO2) can effectively solve the energy crisis caused by fossil resource consumption and the environmental problems arising from the emission of CO2. The electrocatalytic method is currently a promising research method for CO2 reduction; however, it faces the problems of low product selectivity and poor faradaic efficiency (FE). Therefore, the design of effective catalysts with lower overpotential, high FE, and product selectivity is key consideration for the development of electrochemical CO2 reduction (CO2RR). Herein, we summarize the current research progress in the electrocatalytic reduction of CO2 to fuels on heterogeneous catalysts. Progress in the electrocatalytic reduction of two types of products, C1 products (CO, HCOOH, CH3OH, CH4) and C2 products (CH3CH2OH and C2H4), are discussed. The catalytic activity, FE, product selectivity, electrocatalytic mechanisms, and challenges faced in terms of product selectivity and catalytic activity stability in electrochemical CO2 reduction are discussed. This review can provide effective guidance for the design of effective catalysts with high activity, product selectivity, FE, and stability. [ABSTRACT FROM AUTHOR]

All-inorganic perovskites suffer from a phase transition from a cubic α-phase to a tetragonal δ-phase in the ambient atmosphere, although they have the advantage of higher thermal stability. Here, we demonstrated that yttrium-induced perovskite crystallization results in significantly improved phase stability of perovskite even under humid air conditions. Yttrium in precursors was found to impede the crystal growth of perovskite film to stabilize the α-phase of a CsPbI2Br phase and was finally incorporated into the CsPbI2Br perovskite lattice. This structural crystallization process induced by yttrium incorporation gave rise to denser compact films with small grains and host lattice rearrangement by partial substitution for Pb. As a result, a 360-fold phase stability improvement was achieved in humid air with 65% RH compared with the reference film. The favorable electronic structure for efficient electron–hole dissociation and carrier transport to the cathode led to a much-enhanced power conversion efficiency (PCE) of 13.25% after yttrium incorporation compared with only 8.46% for the reference cells in humid air. Moreover, yttrium-incorporated perovskite solar cells (PSCs) without encapsulation exhibited superior long-term stability when stored in ambient air with 65% RH, showing nearly no degradation over 14 h. [ABSTRACT FROM AUTHOR]

Using carbon paste as the back electrode for perovskite solar cells (C-PSCs) has attracted significant attention due to their low cost and excellent stability. In general, the device structure of the fabricated C-PSCs is hole transport layer (HTL) free, and the carbon paste electrodes (CPEs) could directly collect the photo-generated holes. Therefore, interfacial engineering between the perovskite and CPE plays a crucial role in charge collection and affects the performance of C-PSCs. Many studies have been carried out in interfacial engineering so far; however, no review has summarized the work done in this field. Herein, we summarize the continuing progress in interfacial engineering of C-PSCs. Two kinds of contacts have been defined due to the different interfacial contacts in C-PSCs: bi-interfacial and tri-interfacial structures. Techniques for the fabrication of perovskite layers, CPEs, and insulating layers have been discussed for each structure, including the main issues and solutions. Finally, conclusions and perspectives are provided for the future designs and development of C-PSCs. [ABSTRACT FROM AUTHOR]

In this work, a simple interface engineering process for SnO2 electron selective layer (ESL) surface passivation employing a SnCl2 solution is introduced, which has successfully reduced the energy loss for a high open-circuit voltage (Voc) output and consequently improved the performance of all-inorganic CsPbIBr2 perovskite solar cells (PSCs). It was found that surface passivation can effectively suppress the recombination process at the interface between the perovskite and SnO2 due to higher recombination resistance. The shorter PL decay time is attributed to the excellent electron extraction from the perovskite film. After optimizing surface passivation, the power conversion efficiency (PCE) was enhanced from 4.73% to 7.00% and a high Voc of 1.31 V was achieved, which is one of the highest Voc values reported for inorganic Cs-based PSCs. More importantly, the passivated SnO2 based device retains 95.5% of its initial performance at 90 °C in air without encapsulation. This work provides a simple and efficient interface engineering method to improve the Voc and efficiency of all-inorganic PSCs. [ABSTRACT FROM AUTHOR]

Organic–inorganic halide perovskite solar cells (PSCs) have attracted much attention in recent years and their power conversion efficiency (PCE) has rapidly improved from 3.8% to 22.7%. However, the commonly used electron selective layer (ESL), TiO2, requires a high-temperature post-treatment during its preparation process, which is not compatible with flexible PSCs on plastic substrates. Moreover, it is energy intensive and not suitable for the low-cost mass production of PSCs. Developing low-temperature processable ESLs can solve these problems and realize the all-low-temperature fabrication of PSCs. Therefore, in this review, the current progress in low-temperature processed ESLs, especially non-TiO2 inorganic and organic materials and quantum dots (QDs), such as SnO2, ZnO, WOx, CeOx, Nb2O5, In2O3, CdS, Bi2S3, In2S3, Zn2SnO4, fullerene, non-fullerene, CdSe QDs, etc., is summarized. Their preparation methods, properties and applications for use in PSCs are highlighted. Several results obtained by our group are also included. These low-temperature processed ESLs will provide more possibilities for implementing the all-low-temperature fabrication of PSCs with high performances. [ABSTRACT FROM AUTHOR]

One-dimensional MoO2–Co2Mo3O8@C nanorods were synthesized by using MoO3@ZIF-67 composites as a precursor for the first time, and it is found that the Co2Mo3O8 species and its composite have excellent OER activities. The MoO2–Co2Mo3O8@C nanorods present favorable electrocatalytic advantages toward OER in alkaline solution, requiring an overpotential of only 320 mV to deliver a current density of 10 mA cm−2. In addition, the catalyst also shows a small Tafel slope of 88 mV dec−1 and relatively good durability. The attractive OER performance can be attributed to the highly active Co2Mo3O8 and MoO2 species and the unique structure of the catalyst. This strategy can be extended to design and synthesize other novel and highly efficient molybdenum based ternary metal oxides as OER catalysts. [ABSTRACT FROM AUTHOR]

The power conversion efficiency (PCE) of perovskite solar cells (PSCs) can be improved by introducing appropriate additives into perovskite precursor solutions. However, the exact role and mechanism of additives are still unclear. In this study, self-designed cognition experiments were conducted to improve the hole extraction efficiency, as well as to deeply understand the working principle of additives. A common hole transport material, 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl) amino]-9,9′-spirobifluorene (spiro-OMeTAD), was used as an additive for bulk heterojunction PSCs (BHJ-PSCs). The results showed that the PCE of mesoporous BHJ-PSCs (M-BHJ-PSCs) was enhanced by more than 15% when an extremely low concentration of spiro-OMeTAD additive was added. However, the crystallization of the perovskite was hampered and the recombination risk increased when grain boundaries increased in the perovskite layer. Planar BHJ-PSCs were fabricated to further investigate the role of additives. In comparison with those in planar BHJ-PSCs, the hole extraction efficiency and diffusion length significantly improved in M-BHJ-PSCs due to the transport paths and relay effects caused by the spiro-OMeTAD additive. Subsequently, exact functions and a new working principle of additives in BHJ-PSCs were proposed. This study may extend the possibilities of designing highly efficient PSCs through the promotion of additive research and application. [ABSTRACT FROM AUTHOR]

We report a new method to prepare high-quality CH3NH3PbI3 perovskite films under ambient conditions via two-step concentration gradient-controlled reactions. X-ray diffraction and scanning electron microscopy were used to determine their degree of crystallization and microstructures. The results showed that the reactions between CH3NH3I solutions of different concentrations and PbI2 films yielded perovskite films with various degrees of crystallization and surface morphologies. The first-step reaction between a low concentration CH3NH3I solution (6 mg ml−1) and PbI2 films resulted in the formation of large-scale perovskite grains with some PbI2 residue. In addition, the subsequent second-step reaction with a high concentration MAI solution (30 mg ml−1) achieved good crystallization and full coverage of the perovskite films on the substrates. The average grain size of the CH3NH3PbI3 perovskite films prepared from this concentration gradient method reached 1.4 μm, and they also showed reduced overall grain boundaries. Enhanced spectral absorption in the long-wavelength region was also observed for the large-grain perovskite films due to the grain size-dependent light scattering. Moreover, the comparison between AM1.5G sunlight and the spectral absorption indicated that it might benefit the efficient power conversion of solar cells. Even though processed under ambient conditions with a high humidity of ca. 75%, the solar cells fabricated from these films exhibited enhanced photovoltaic performance compared with those constructed using the single solution method, reaching a power conversion efficiency of 11.48%. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have gained tremendous research interest in recent several years. To date the power conversion efficiency (PCE) of PSCs has been increased from 3.8% to over 22.1%, showing that they have a promising future as a renewable energy resource to compete with conventional silicon solar cells. However, a crucial challenge of PSCs currently is that perovskite materials and PSCs have limitations of easy degradation and inferior long-term stabilities, thus hampering their future commercial applications. In this review, the degradation mechanisms for instable perovskite materials and their corresponding solar cells are discussed. The stability study of perovskite materials and PSCs from the aspect of experimental tests and theoretical calculations is reviewed. The strategies for enhancing the stability of perovskite materials and PSCs are summarized from the viewpoints of perovskite material engineering, substituted organic and inorganic materials for hole transportation, alternative electrodes comprising mainly carbon and its relevant composites, interfacial modification, novel device structure construction and encapsulation, etc. Various approaches and outlooks on the future direction of perovskite materials and PSCs are highlighted. This review is expected to provide helpful insights for further enhancing the stability of perovskite materials and PSCs in this exciting field. [ABSTRACT FROM AUTHOR]

The ideal liquid–solid heterogeneous electrocatalysis should have not only high catalytic activity but also free electron transport. However, preparing a single catalyst that simultaneously possesses both advantages has proven to be challenging. Herein, we prepared nano–micro composite catalysts (NMCCs) composed of highly dispersed Fe3O4 nanoparticles fixed on reduced graphene oxide (RGO) sheets (namely Fe3O4@RGO-NMCC) as the counter electrode (CE) in dye-sensitized solar cells (DSCs). Compared with the Fe3O4 or RGO CE, the Fe3O4@RGO-NMCC CE exhibited improved activity and reversibility for the catalytic reduction of triiodide ions (I3−) to iodide ions (I−). Notably, DSCs using rigid and flexible Fe3O4@RGO-NMCC CEs achieved high PCEs up to 9% and 8% on fluorine-doped tin oxide (FTO)/glass substrates and flexible polymer substrates, respectively. These values are, to our knowledge, some of the highest reported efficiencies for DSCs based on a flexible Pt-free CE. We ascribed the superior catalytic performance of Fe3O4@RGO-NMCC to faster electron hopping between Fe2+ and Fe3+ and free electron transport by broad RGO sheets. Finally, Fe3O4@RGO-NMCC exhibited good stability in the practical application of DSCs because Fe3O4 nanoparticles were chemically bonded to the surface of RGO. Our work here will be of great interest for fundamental research and practical applications of Fe3O4 in lithium batteries, splitting water and magnetic fields. [ABSTRACT FROM AUTHOR]

As a conceptually new class of 2D materials, inorganic graphene analogue (IGA) ultrathin nanosheets perform an increasingly vital function in various electronic devices. However, the relatively low electrical conductivity of IGA ultrathin nanosheets severely hampers their application as electrode materials in devices. Through in situ synthesis, we report the combination of inorganic graphene and graphene into atomically thin nanosheets as efficient electrocatalysts for the oxygen reduction reaction (ORR). Benefitting from the advantages of both IGAs and reduced graphene oxide, the g–MoSe2 and g–WSe2 nanocomposites showed excellent ORR activity associated with a number of exchanged electrons close to four, which corresponded to the complete reduction of oxygen into water. In particular, the two electrocatalysts exhibited a positive onset potential of −0.02 V (close to that of Pt/C, 0.02 V) and a high kinetic current density (JK) of 10.22 mA cm−2 for g–MoSe2 and 10.77 mA cm−2 for g–WSe2 at −0.20 V. Compared with commercial Pt/C, these catalysts possess outstanding long-term durability and fuel crossover resistance capacity in alkaline media. Therefore, nanocomposites of inorganic graphene and graphene can be developed into low-cost and efficient alternatives (to the noble metal Pt) to be used as cathodic electrodes in fuel cells. [ABSTRACT FROM AUTHOR]