熵增工程在电催化反应中的研究进展

Progress on Entropy Production Engineering for Electrochemical Catalysis

目前对高性能与高稳定性的电催化剂进行精准合成仍然是亟待解决的问题。熵作为是最重要的热力学参数之一,是描述体系无序程度的物理量,其数值主要由材料的结构、磁矩、原子和电子振动共同决定。根据体系的构型熵值,我们通常将材料分为低熵材料(ΔS_(mix)<1R)、中熵材料(1R≤ΔS_(mix)≥1.5R)和高熵材料(ΔS_(mix)>1.5R)。随着熵值的增加,材料本征的物理与化学性质也会随之发生相应的变化。得益于不同金属元素的共存,在界面处原子级的多组分排列,所产生的协同性高熵效应能够有效地提升电催化反应的活性,因此在电催化领域中得到了广泛的研究关注。本综述对高熵电催化剂的基本概念、合成路线(“自上而下”与“自下而上”)以及在不同电催化反应类型中的高熵材料结构与性能之间的构效关系进行了系统总结,主要包括析氢(HER)、析氧(OER)、氧还原(ORR)、醇氧化(AOR)、氮还原(NRR)和二氧化碳还原反应(CO_(2)RR)等,从而阐明熵增工程对高性能电催化剂设计与应用的优势与潜力。同时,针对目前高熵催化剂研究所面临的主要问题与挑战,对未来基于熵增工程的高熵电催化剂的设计思路与合成方法进行展望。

As for the accurate synthesis of high-performance electrochemical catalysts with good robustness,the rational design on atomic level is still a priority.Entropy,as one of the most significant thermodynamic parameters,measure the disorder of a system,which is a significant quantity for materials.The values are primarily determined by the crystal structure,magnetic moments and the atomic and electronic vibrations of the materials.According to the configurational entropy of the system,we usually divide the material into low entropy materials(LEMs)(ΔS_(mix) < 1R),medium entropy materials(MEMs)(1R ≤ ΔS_(mix) ≥ 1.5R) and high entropy materials(HEMs)(ΔS_(mix) > 1.5R),where R is the gas molar constant.HEMs are those that consist of five or more major elements of roughly equal proportion,in a highly uniform,random manner,which typically consist of one or two major elements compared to traditional materials.As the entropy value increases,the intrinsic physical,chemical and structural properties of the material change accordingly,resulting in special physicochemical properties(e.g.,strength,electrical conductivity,corrosion resistance,etc.).Moreover,due to its multi-element combination,the HEMs can be precisely regulated by selecting different elements and their ratios according to the needs,which overcomes the limitations of the traditional catalysts in terms of relatively single component,structure and field of application.Importantly,the synergistic high entropy effect and multi-component arrangement at the atomic-level interface produced by the coexistence of different metal elements in HEMs can exert higher catalytic activity,selectivity and stability in different reactions.This has attracted a lot of attention from researchers,especially in the field of electrocatalysis.In this review systematically summarizes the fundamental concepts of high-entropy catalysts(HECs),synthetic approaches(“topdown” and “bottom-up”),and the structure-performance relationships of HEMs in different types of electrocatalytic processes,mainly including hydrogen evolution reaction(HER),oxygen evolution reaction(OER),oxygen reduction reaction(ORR),alcohol oxidation reaction(AOR),nitrogen reduction reaction(NRR),and carbon dioxide reduction reaction(CO_2RR) etc.Thus,the advantages and potential of high-performance electrocatalysts based on entropy increase engineering are illuminate.At the same time,it is summarized and discussed that HECs are currently facing problems and challenges such as complicated material rational design,complex preparation process,the mechanism of electrocatalytic processes in which multiple metal elements interact is ambiguous,and poor stability under extreme reaction conditions.Finally,the main problems and challenges facing the current HECs research.We look forward to the future design ideas,synthesis methods different research areas and industrial applications of HECs based on entropy enhancement engineering.