Oxygen defect-stabilized heterogeneous single atom catalysts: preparation, properties and catalytic application

Single atom catalysts (SACs) show outstanding activity and selectivity in chemical catalysis owing to their unique electronic structure and unsaturated coordination environment, in which every dispersed metal species on the support can serve as catalytic centers to achieve maximum atomic utilization efficiency. However, fabricating SACs with high atomic dispersion is still challenging owing to their extremely high surface energy. In various synthetic strategies of SACs, benefitting from the high active site density, chemoselectivity and stability, anchoring single metal atoms on oxygen defective supports has attracted increasing attention. In this review, the synthetic strategies developed to design oxygen defect-SACs with a stable structure are firstly presented. Then we highlight significant progress made in oxygen defect-stabilized single atomic catalysts with special focus on the effects of the electronic structure of oxygen defects on the stabilization of metal species. Furthermore, we summarize the characterization methods of oxygen vacancies and discuss the recent applications of as-prepared SACs with emphasis on the crucial role of strong interactions between single metal atoms and oxygen defects in the improvement of activity in heterogeneous catalysis. Finally, the key challenge and future opportunities for the development of this field are identified. We believe that this will promote the development of this fertile research area in future.