氧化物负载单原子电解水催化剂的载体效应

Support effects of oxide-supported single-atom water electrolysis catalysts

单原子催化剂(SACs)由于其原子利用率高、活性中心明确、比活性高和稳定性强等优点,在催化电解水领域具有独特的优势.然而,材料中的金属-载体相互作用对催化过程具有重大影响.首先,本文明确了单原子催化剂的特点并研究了其电子结构和构效关系方面独特优势.其次综述了氧化物载体在稳定金属单原子、分散活性物种、调节中心电子结构、吸附和活化反应物等方面的重要作用;并详细分析了载体如何通过结构缺陷、表面基团、空间限域和晶格作用等实现对金属原子的负载和稳定.然后,通过实例对比了单原子在不同氧化物载体上配位结合方式,以及在析氢、析氧和全水解反应中的性能差异.最后,对利用载体与单原子相互作用调节催化剂性能的机遇和挑战、关键问题和可能的解决方案进行了展望.

Single-atom catalysts(SACs) have unique advantages in the catalytic electrolysis of water owing to their high atomic utilization rate,clear active centers,high specific activity,and excellent stability.Notably,metal–support interactions in the materials have significant influences on the catalytic process.However,the interaction mechanisms between supports and metal active sites,as well as the influences of supports on the intrinsic activity of real active sites,have not been fully explained by previous studies.SACs have clear coordination structures with supports,which can accurately adjust the metal–support binding modes,thereby thoroughly tailoring the electronic and magnetic structures of the electrocatalysts.This will essentially solve the issues faced by electrolytic water(hydrogen evolution reaction(HER),oxygen evolution reaction(OER),and overall water splitting) catalysts.Given the unique features of metal oxides,such as surface acidity,alkalinity,and redox properties,metal oxides are regarded as one of the most popular and promising types of supports.The objective of this review is to present a detailed analysis of the support effects of oxide-supported singleatom water electrolysis catalysts.In this article,first,we identified the characteristics of SACs and their unique advantages by examining the electronic structure and structure–activity relationship in electrocatalysis.Subsequently,we summarized the three critical roles of supports in determining the coordination structure of catalytic metal centers and their catalytic performance.(1) As a carrier or substrate to disperse and stabilize the active species,the mechanical strength of the catalyst is increased,and the dissolution and aggregation of single atoms are inhibited.(2) Adjusting the coordination or atomic structure through electronic and spatial effects activates the catalytic reaction centers and improves reactant adsorption.(3) The atoms in the support near the center of a single atom are also activated and directly participate in chemical reactions.Moreover,the methods through which metal oxides support the single atoms are reviewed and can be categorized into four types:(1) by loading single atoms through surface defects;(2) by stabilizing single atoms through interactions produced between metals and surface groups and ligands;(3) by confining single atoms owing to spatial limitations of porous nanostructures;and(4) by substituting single atoms within their crystal lattices.The clarification of interactions offers a more theoretical and practical reference for accurately controlling the electronic structure of metal–support interfaces on the atomic and molecular scales.Moreover,the differences in coordination and binding of single atoms on different supports were also analyzed by providing examples.Thus,it can be safely concluded that the changes in electronic structures through strong bonding or electronic interactions between supports and active centers can optimize the chemical adsorption of reactant molecules or intermediates and accelerate water dissociation,finally realizing improved performance toward HER,OER,and overall water splitting reactions.Finally,the opportunities and challenges,key issues,and possible solutions for adjusting the performance of catalysts through interactions between supports and single atoms were prospected.