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Water electrolysis is a promising method for efficiently producing hydrogen and oxygen, crucial for renewable energy conversion and fuel cell technologies. The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are two key electrocatalytic reactions occurring during water splitting, necessitating the development of active, stable, and low-cost electrocatalysts. Transition metal (TM)-based electrocatalysts, spanning noble metals and TM oxides, phosphides, nitrides, carbides, borides, chalcogenides, and dichalcogenides, have garnered significant attention due to their outstanding characteristics, including high electronic conductivity, tunable valence electron configuration, high stability, and cost-effectiveness. This timely review discusses developments in TM-based electrocatalysts for the HER and OER in alkaline media in the last 10 years, revealing that the exposure of more accessible surface-active sites, specific electronic effects, and string effects are essential for the development of efficient electrocatalysts towards electrochemical water splitting application. This comprehensive review serves as a guide for designing and constructing state-of-the-art, high-performance bifunctional electrocatalysts based on TMs, particularly for applications in water splitting. [ABSTRACT FROM AUTHOR]

The surface atomic arrangement and defective structures of electrocatalysts play a crucial role in determining their catalytic activity and selectivity. Hematite (α-Fe2O3) nanostructures with oxygen vacancies are promising electrocatalysts for the oxygen reduction reaction (ORR) due to their low-cost and environmental friendliness. However, a systematic study of their ORR performance, especially selectivity at high oxygen vacancy concentrations, is still lacking. In this study, we synthesized α-Fe2O3 nanosheets with surface oxygen vacancies using a simple solvothermal reaction followed by a liquid phase NaBH4 reduction method. The oxygen vacancy amount was adjusted by varying the concentrations of NaBH4 solution, and it was found that increasing the oxygen vacancy concentration from 11.4% to 43.4% improved the ORR activity, but further increasing it to 77.3% deteriorated the crystalline quality and thus affected the ORR performance. The optimized sample (α-Fe2O3-1 M), treated with a 1 M NaBH4 solution, showed a high limiting current density of 5.75 mA cm−2 at 0.4 V vs. the reversible hydrogen electrode (RHE). The observed enhancement in ORR activity can be attributed to the optimal surface oxygen vacancies, which improve catalytic kinetics and increase the exposure of active sites. [ABSTRACT FROM AUTHOR]

Oxide perovskites have emerged as an important class of materials with important applications in many technological areas, particularly thermocatalysis, electrocatalysis, photocatalysis, and energy storage. However, their implementation faces numerous challenges that are familiar to the chemist and materials scientist. The present work surveys the state-of-the-art by integrating these two viewpoints, focusing on the critical role that defect engineering plays in the design, fabrication, modification, and application of these materials. An extensive review of experimental and simulation studies of the synthesis and performance of oxide perovskites and devices containing these materials is coupled with exposition of the fundamental and applied aspects of defect equilibria. The aim of this approach is to elucidate how these issues can be integrated in order to shed light on the interpretation of the data and what trajectories are suggested by them. This critical examination has revealed a number of areas in which the review can provide a greater understanding. These include considerations of (1) the nature and formation of solid solutions, (2) site filling and stoichiometry, (3) the rationale for the design of defective oxide perovskites, and (4) the complex mechanisms of charge compensation and charge transfer. The review concludes with some proposed strategies to address the challenges in the future development of oxide perovskites and their applications. [ABSTRACT FROM AUTHOR]

Precise control over the morphology of nanomaterials is critical yet challenging. The present work reports an efficient approach to tailor the architecture of nanostructures. The process involves rapid disassembly/reassembly of an unstable metal-based coordination polymer (MCP) by controlling the kinetics of the reassembly process. The synthesis procedure delivers unprecedented polycrystalline nanostructures, e.g., holey 2D CeO2−x nanosheets, with precisely tailored thicknesses in the range of 10–100 nm, and hollow 3D pseudo-octahedra and spheres. The consequent high surface areas and pore volumes, short diffusion distances, and high defect densities of the holey 2D CeO2−x indicate significant densities of active sites. This holey architecture exhibits rapid CO conversion and outstanding solar light photocatalytic performance. This approach of directed assembly offers a template-free, controllable, and cost-effective approach to achieve engineered CeO2−x architectures, which are nearly impossible through existing approaches. [ABSTRACT FROM AUTHOR]

A series of unsupported and supported vanadium phosphorus oxide catalysts were prepared by employing a new strategy, which significantly reduced the complexity of catalyst preparation. The greatly simplified catalyst fabrication benefits a greener and lower-cost process for practical applications. The currently fabricated systems showed ca. 90% target product(s) selectivity with a promising yield as well as catalyst durability. [ABSTRACT FROM AUTHOR]

Due to their high efficiency and stability, triple-cation based perovskite solar cells (PSCs) have now crossed 23% power conversion efficiency (PCE). However, the perovskite composition and type of the electron transport layer (ETL) play a key role in improving their performance. Therefore, in the present investigation, high quality TiO2/SnO2 bilayer ETLs and thermally stable reduced methylammonium (MA) cation based triple-cation perovskite layers are used to fabricate thermally stable PSCs. By retaining their normal (n–i–p) device architecture, the influence of antisolvents on the perovskite layer has been investigated in detail. Systematic studies in this work reveal that the amorphous SnO2/TiO2 bilayer and the trifluorotoluene (TFT) processed perovskite layer significantly influence the current density and open circuit voltage (VOC) and reduce the charge recombination of perovskite devices. The optimised devices having micrometer size grains exhibited ＞20.5 ± 0.5% PCE for a thermally stable Rb0.05(FAPbI3)0.95(MAPbBr3)0.05 perovskite composition with a SnO2/TiO2 bilayer ETL. Furthermore, the SnO2:TiO2 bilayer ETL-containing PSCs are thermally stable for more than 200 hours at 80 °C. [ABSTRACT FROM AUTHOR]

Despite the fact that its crystal state is thermodynamically stable, Cu64Zr36 alloy is prone to form metastable glass at a high cooling rate. However, the confinement can induce nano-crystallization with a novel sandwich-like hierarchical structure consisting of pure Cu layers, pure Zr layers and mixed layers by conducting molecular dynamics simulations. The liquid-to-crystal transition temperature and interatomic repulsion softness display abnormal oscillations, instead of monotonous variation, as the wall–wall separation increases. When the confinement size is 10 Å and 12 Å, the transition temperature reaches a maximum, resulting from the pending new sandwich layer. The atomic movement and dynamical heterogeneity are demonstrated to play a vital role in the abnormal oscillation behavior of physical properties of the nano confined metallic glass. The sandwich-like structure can alter the Cu–Zr bond fraction, which eventually influences the liquid-to-crystal transition temperature and interatomic repulsion softness. Our findings provide a deep insight into the hierarchical nanostructures and its liquid-to-crystal transition characteristics under confinement at the atomic level. [ABSTRACT FROM AUTHOR]

This feature article summarizes the recent progress in porous perovskite oxides as advanced catalysts for both energy conversion applications and various heterogeneous reactions. Recently, research has been focused on specifically designing porous perovskite materials so that large surface areas can be harnessed and surface properties can be improved. Numerous potential applications of porous perovskites have been investigated, including heterogeneous catalysis and air battery applications that rely on interactions and/or reactions of other components with porous perovskites. The main objective of this article is to examine the progress of recent research studies on porous perovskite nanomaterials, including the preparation methods and their applications in catalysis and batteries. The wide variety of the related knowledge on porous mixed oxides can provide guidance for researchers with interests ranging from the design of functionalized materials to the field of heterogeneous catalysis and electrochemical applications. [ABSTRACT FROM AUTHOR]

Ordered meso/macroporous metal oxides have gained increasing attention in heterogeneous catalysis arising from their large surface areas and pore volumes, elevated catalytic activity and good thermal stability. Compared to nonporous metal oxides, their most prominent feature is the ability to interact with molecules not only at their exterior surface but also within the large interior surface of the material. The past decade has witnessed substantial advances in the synthesis of new porous metal oxides with ordered structures for use in a wide range of applications. By recalling some of the classical fundamentals of porous materials, this review examines the recent developments in ordered meso- and macro-porous metal oxide catalysts for heterogeneous catalysis. Additionally, we outline the current challenges in the field of nanoparticle-based catalysis, including the role played by the morphology (size, shape, and porosity) of ordered meso/macroporous metal oxides, and provide a perspective on the need for further advances in porous materials so that their contribution to heterogeneous catalysis can continue to expand. [ABSTRACT FROM AUTHOR]

Highly dispersed Ag nanoparticles supported on high-surface-area 3DOM La0.6Sr0.4MnO3 were successfully generated via the dimethoxytetraethylene glycol-assisted gas bubbling reduction route. The macroporous materials showed super catalytic performance for methane combustion. [ABSTRACT FROM AUTHOR]

Li 7 La 3 Zr 2 O 12 (LLZO)-based solid-state Li batteries (SSLBs) have emerged as one of the most promising energy storage systems due to the potential advantages of solid-state electrolytes (SSEs), such as ionic conductivity, mechanical strength, chemical stability and electrochemical stability. However, there remain several scientific and technical obstacles that need to be tackled before they can be commercialised. The main issues include the degradation and deterioration of SSEs and electrode materials, ambiguity in the Li + migration routes in SSEs, and interface compatibility between SSEs and electrodes during the charging and discharging processes. Using conventional ex situ characterization techniques to unravel the reasons that lead to these adverse results often requires disassembly of the battery after operation. The sample may be contaminated during the disassembly process, resulting in changes in the material properties within the battery. In contrast, in situ / operando characterization techniques can capture dynamic information during cycling, enabling real-time monitoring of batteries. Therefore, in this review, we briefly illustrate the key challenges currently faced by LLZO-based SSLBs, review recent efforts to study LLZO-based SSLBs using various in situ / operando microscopy and spectroscopy techniques, and elaborate on the capabilities and limitations of these in situ / operando techniques. This review paper not only presents the current challenges but also outlines future developmental prospects for the practical implementation of LLZO-based SSLBs. By identifying and addressing the remaining challenges, this review aims to enhance the comprehensive understanding of LLZO-based SSLBs. Additionally, in situ / operando characterization techniques are highlighted as a promising avenue for future research. The findings presented here can serve as a reference for battery research and provide valuable insights for the development of different types of solid-state batteries.

Aluminum trimesate-based MOF (MIL-96-(Al)) has attracted intense attention due to its high chemical stability and strong CO 2 adsorption capacity. In this study, CO 2 capture and selectivity of MIL-96-Al was further improved by the coordination of the second metal Ca. To this end, a series of MIL-96(Al)-Ca were hydrothermally synthesised by a one-pot method, varying the molar ratio of Ca 2+ /Al 3+ . It is shown that the variation of Ca 2+ /Al 3+ ratio results in significant changes in crystal shape and size. The shape varies from the hexagonal rods capped in the ends by a hexagonal pyramid in MIL-96(Al) without Ca to the thin hexagonal disks in MIL-96(Al)-Ca4 (the highest Ca content). Adsorption studies reveal that the CO 2 adsorption on MIL-96(Al)-Ca1 and MIL-96(Al)-Ca2 at pressures up to 950 kPa is vastly improved due to the enhanced pore volumes compared to MIL-96(Al). The CO 2 uptake on these materials measured in the above sequence is 10.22, 9.38 and 8.09 mmol g -1 , respectively. However, the CO 2 uptake reduces to 5.26 mmol g -1 on MIL-96(Al)-Ca4. Compared with MIL-96(Al)-Ca1, the N 2 adsorption in MIL-96(Al)-Ca4 is significantly reduced by 90% at similar operational conditions. At 100 and 28.8 kPa, the selectivity of MIL-96(Al)-Ca4 to CO 2 /N 2 reaches up to 67 and 841.42, respectively, which is equivalent to 5 and 26 times the selectivity of MIL-96(Al). The present findings highlight that MIL-96(Al) with second metal Ca coordination is a potential candidate as an alternative CO 2 adsorbent for practical applications., Competing Interests: The authors declare no conflict of interest., (This journal is © The Royal Society of Chemistry.)

Highly dispersed Ag nanoparticles supported on high-surface-area 3DOM La0.6Sr0.4MnO3 were successfully generated via the dimethoxytetraethylene glycol-assisted gas bubbling reduction route. The macroporous materials showed super catalytic performance for methane combustion.