Tailoring Single-metal Atom Catalysts: A Strategic Defects Engineering Approach for Electrochemical Reduction Reactions

Abstract

Single metal atom catalysts (SMAC) are gaining attention as a promising material in chemical transformation and energy conversion technologies due to their well-defined geometric structures and efficient atom utilization. The rational design and incorporation of SMAC into diverse support materials, including carbon materials, two-dimensional (2D) materials and metal oxides, is critical to increase their active-site density. This enhancement is essential for maximizing the effectiveness and selectivity of SMAC. However, there are challenges in preparation of single-atom metal catalysts where each active metal site exhibits tremendous amount of free energy, leading to agglomeration. This review paper discusses the importance of defects to introduce a micro coordination environment in a wide range of materials in order to enhance the stabilizing process with SMAC. The introduction of defects in the preparation of SMAC has validated its success as a successful scientific approach in the enhancement of the uniform dispersion of SMAC. In this paper, we have investigated the role of several kinds of defects, such as vacancies, heteroatom doping, and intrinsic defects, on porous carbons, graphene, two-dimensional transition metal dichalcogenides (TMDs) and metal oxide substrates to accommodate and achieve optimal loading of SMAC. To provide a fresh perspective, we emphasize several non-conventional schemes regarding defect-inducing techniques, such as the electrochemical method, plasma method, ion-radiation method, and etch evaporation process. Furthermore, the mechanism of the defect engineering is explored in detail by analyzing the electronic structure as well as Fermi level of metal atoms by advanced characterization. This review addresses the future challenges in the field of SMAC and summarizes the meaningful findings about the role of defects on supports stabilizing SMAC. According to our knowledge, a detailed review that thoroughly discusses the relationship between defects in wide range of substrates and single atom metals (both noble and non-noble), and their collective impact on electrochemical reduction reactions, gas sensing and anti-infection therapy is limited. This study widens the opportunities for the more efficient synthesis of SMAC and maximizes its utilization across a diverse spectrum of applications encompassing catalysis, energy conversion, and environmental monitoring.