Fabrication of High-Loading Single Atom Catalysts for Energy-related Catalysis

Heterogeneous single-atom catalysts (SACs) have emerged as a new frontier in the field of energy-related catalysis owing to the maximum atomic utilization efficiency, unique electronic and geometric properties compared with traditional nano-catalysts. Nevertheless, it is still a great challenge to fabricate high-loading SACs, since these isolated metal sites with high surface free energy are apt to assemble into clusters or particles with a high metal content. This review summarizes recent advancements for high-loading SACs, and mainly focuses on the synthetic strategies, unique interatomic interactions, together with their applications in different chemical reactions, including photocatalysis, electrocatalysis, and thermocatalysis. Specifically, strategies that consist of wet-chemistry, atomic layer deposition, ball milling, pyrolysis, chemical vapor deposition, laser ablation, and electrodeposition are first overviewed for the preparation of high-loading SACs. Unique interatomic interactions in high-loading SACs in terms of charge transfer and variations in energy band structure, spin state and reaction pathways are further described. Then, examples of high-loading SACs in heterogeneous catalysis are discussed to illustrate the relation between their geometric and electronic properties and catalytic performance as well as the reaction mechanism. Finally, a conclusion of this review and insights into the challenges and prospects in this area are also proposed.