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High entropy materials (HEMs) compositing of at least five elements have gained widespread attention in the field of electrocatalysis due to their tunable activities and high stability. These intrinsic properties can be further highlighted when the size of HEMs comes to the nanoscale. In nanostructured HEMs, the fascinating properties including large composition space, multi‐element synergy, and high configuration entropy are expected to endow nano‐HEMs with excellent catalytic activity and stability, thus providing greater potential for the design of advanced electrocatalysts. In this review, nano‐HEMs are differentiated in detail in dimensions and the common synthesis methods are summarized. Additionally, from the perspective of the complex nanostructure‐performance relationship, the applications of nano‐HEMs in electrocatalysis systems, including water‐splitting (hydrogen evolution reaction (HER), oxygen evolution reaction (OER)), hydrogen oxidation reaction (HOR), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO2RR), nitrogen reduction reaction (NRR) and alcohol oxidation reaction (AOR) are discussed. Finally, the main challenges faced by nano‐HEMs electrocatalysis are underscored. This review is expected to provide more insights into understanding and developing efficient electrocatalytic materials for practical applications. [ABSTRACT FROM AUTHOR]

Electrolytic water splitting using renewable energy sources, such as solar power, provides a green and sustainable approach for hydrogen production. Anion exchange membrane (AEM) electrolyzers present substantial commercial prospects; however, the rate of hydrogen evolution reaction (HER) in alkaline electrolytes is limited by the water dissociation step. In this work, we fabricated an N-doped Ni substrate for loading ultrafine Pt nanoparticles, realizing spatial decoupling of the reaction process to break the limitation of water dissociation, where the N-doped Ni substrate and Pt nanoparticles facilitate the supply of ample H* and H2 release, respectively. The prepared Pt–N–Ni/NC with extremely low Pt loading (1.0 wt%) requires only 15 and 149 mV overpotentials to reach current densities of 10 and 1000 mA cm−2, respectively. When assembled into an AEM electrolyzer, the system requires a cell voltage of only 1.75 V to achieve a current density of 1000 mA cm−2. Notably, the solar-driven AEM electrolyzer demonstrates a current density of 1390 mA cm−2 with a solar-to-hydrogen efficiency (STH) of 8.27%. This study proposes a strategy to achieve efficient utilization and performance improvement of precious metals, promoting the development of efficient green hydrogen production. [ABSTRACT FROM AUTHOR]

In the electrocatalytic CO2 reduction reaction (CO2RR), metal catalysts with an oxidation state generally demonstrate more favorable catalytic activity and selectivity than their corresponding metallic counterparts. However, the persistence of oxidative metal sites under reductive potentials is challenging since the transition to metallic states inevitably leads to catalytic degradation. Herein, a thorough review of research on oxidation-state stabilization in the CO2RR is presented, starting from fundamental concepts and highlighting the importance of oxidation state stabilization while revealing the relevance of dynamic oxidation states in product distribution. Subsequently, the functional mechanisms of various oxidation-state protection strategies are explained in detail, and in situ detection techniques are discussed. Finally, the prevailing and prospective challenges associated with oxidation-state protection research are discussed, identifying innovative opportunities for mechanistic insights, technology upgrades, and industrial platforms to enable the commercialization of the CO2RR. [ABSTRACT FROM AUTHOR]

Electrolysis that reduces carbon dioxide (CO2) to useful chemicals can, in principle, contribute to a more sustainable and carbon-neutral future1–6. However, it remains challenging to develop this into a robust process because efficient conversion typically requires alkaline conditions in which CO2 precipitates as carbonate, and this limits carbon utilization and the stability of the system7–12. Strategies such as physical washing, pulsed operation and the use of dipolar membranes can partially alleviate these problems but do not fully resolve them11,13–15. CO2 electrolysis in acid electrolyte, where carbonate does not form, has therefore been explored as an ultimately more workable solution16–18. Herein we develop a proton-exchange membrane system that reduces CO2 to formic acid at a catalyst that is derived from waste lead–acid batteries and in which a lattice carbon activation mechanism contributes. When coupling CO2 reduction with hydrogen oxidation, formic acid is produced with over 93% Faradaic efficiency. The system is compatible with start-up/shut-down processes, achieves nearly 91% single-pass conversion efficiency for CO2 at a current density of 600 mA cm−2 and cell voltage of 2.2 V and is shown to operate continuously for more than 5,200 h. We expect that this exceptional performance, enabled by the use of a robust and efficient catalyst, stable three-phase interface and durable membrane, will help advance the development of carbon-neutral technologies.We develop a proton-exchange membrane system that reduces CO2 to formic acid at a catalyst that is derived from waste lead–acid batteries and in which a lattice carbon activation mechanism contributes. [ABSTRACT FROM AUTHOR]

Electrocatalytic carbon monoxide reduction has been previously reported to yield a range of carbonaceous products including alcohols, hydrocarbons and carboxylic acids. However, esters, an important family of organic compounds, have not been formed. Herein, we report the electrosynthesis of C3 to C6 acetate esters (H3C−(C=O)−O−R) from carbon monoxide using copper catalysts in a membrane electrode assembly cell. Ethyl acetate and propyl acetate could be produced with an unprecedented total Faradaic efficiency (FE) of ∼22 % and with a current density of up to −55 mA cm−2, alongside minor quantities of methyl acetate and butyl acetate. The esters are produced via the addition reaction of ethenone (H2C=C=O) and alcohols produced during CO reduction. We show that the near water‐free reaction conditions and the high local pH play key roles in the formation of the esters. [ABSTRACT FROM AUTHOR]

Van der Waals (vdW) heterojunction has played an essential role in effectively utilizing solar energy for sustainable hydrogen production. Herein, a 2D/2D g‐C3N4/SnS2 photocatalyst with vdW heterojunction is developed by self‐assembly contacting SnS2 hexagonal nanoplates and g‐C3N4 nanosheets. A reasonable Type‐II charge transfer mechanism based on the vdW heterostructure is proposed and verified by hydroxyl radical generation test. Photocatalysts with vdW heterostructure enable high‐efficiency H2 production under the visible light illumination, of which the optimized rate is about seven times higher than that of SnS2. Experimental analysis and corresponding density functional theory simulation jointly identify that enhanced photocatalytic activity is ascribed to the optimized behavior of photogenerated carriers and promotional interaction between reactants with catalysts. Specifically, charge redistribution and staggered band structure of the heterojunction intrinsically facilitate the efficient interfacial charge migration and separation. Diminished free energy of surface hydrogen adsorption reveals the easier hydrogen adsorption‐desorption for a composite system from the viewpoint of thermodynamics. This work may be attractive for the implementation of rationally synthesizing catalysts for efficient photocatalytic water splitting. [ABSTRACT FROM AUTHOR]