Recent advances in cation effects for electrocatalytic reduction reactions

Electrochemical technologies offer a promising approach for the effective storage, conversion, and utilization of renewable energy with low carbon emissions. Among these technologies, electrocatalytic reduction, which directly uses water as a hydrogen source, is recognized as an environmentally friendly and sustainable method. Recently, tuning the cation in the electrolyte has emerged as an effective strategy to improve electrocatalytic activity and selectivity. At the electrode-electrolyte interface, cations in the electrolyte can affect the surface charge of electrodes, the dielectric constant of electrolyte solutions, and non-covalent interactions between ions and water molecules, thereby influencing catalyst activity and selectivity.

Recently, a research team led by Prof. Mingfei Shao from Beijing University of Chemical Technology, China, provided a comprehensive overview of the cation effects on catalytic reduction reactions. This review covers mechanisms, applications, characterization techniques, and computational simulations of cation effects in electrocatalytic reduction reactions, as well as the challenges and prospects in this field. This work was published in Chinese Journal of Catalysis (https://doi.org/10.1016/S1872-2067(24)60080-X).

Cation effects are diverse and can be categorized into several aspects: (1) adsorption/stabilization of reactants/intermediates, (2) tuning the local electric field, (3) buffering the interfacial pH, and (4) influencing the HER activity during reduction reactions. By modulating factors such as the type and concentration of cations, the catalytic activity, selectivity, and Faradaic efficiency of reduction reactions can be significantly improved. Cation effects can be applied in various electrocatalytic reactions (e.g., CO₂ reduction, N₂/NO_x reduction, organic reduction, and oxygen reduction). Additionally, both ex-situ and in-situ characterization techniques can efficiently and directly detect the influence of cations on reactions. Theoretical insights into cation effects can also be gained through computational simulations, such as ab initio molecular dynamics (AIMD) and COMSOL Multiphysics simulations. In summary, this review provides a comprehensive overview of the roles of cation effects in electrocatalytic reduction reactions.

Although significant breakthroughs have been made to enhance catalytic activity and explain cation effects, there are still some problems that remain to be resolved. (1) Accurately uncovering the specific mechanisms of the interfacial electric field effect in reaction mechanisms remains challenging due to the complexity of the reaction interface, highlighting the need for more in-depth studies. (2) It is essential to develop new characterization methods to identify the primary mechanisms of specific reaction/cation systems under real operating conditions. (3) Catalyst design strategies should be explored and developed further, with a focus on advanced modification techniques to achieve catalysts with high stability. (4) Expanding the application of cation effects to other catalytic fields, such as electrocatalytic oxidation and photocatalysis, is necessary. (5) Investigating the dynamic changes in the phase structure of catalysts caused by cation insertion during electrocatalysis is crucial. This review provides fundamental insights and design guidance for applying cation effects, further driving the development of this field.

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This work was supported by the National Natural Science Foundation of China (22090031, 22108008, 22302006, 22288102), the Young Elite Scientist Sponsorship Program by CAST (2021QNRC001), the Fundamental Research Funds for the Central Universities (buctrc202011), and the National Funded Postdoctoral Researchers Program (GZB20230049).

About the Journal

Chinese Journal of Catalysis is co-sponsored by Dalian Institute of Chemical Physics, Chinese Academy of Sciences and Chinese Chemical Society, and it is currently published by Elsevier group. This monthly journal publishes in English timely contributions of original and rigorously reviewed manuscripts covering all areas of catalysis. The journal publishes Reviews, Accounts, Communications, Articles, Highlights, Perspectives, and Viewpoints of highly scientific values that help understanding and defining of new concepts in both fundamental issues and practical applications of catalysis. Chinese Journal of Catalysis ranks among the top one journals in Applied Chemistry with a current SCI impact factor of 15.7. The Editors-in-Chief are Profs. Can Li and Tao Zhang.

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