Advances in single-atom catalysts: Design, synthesis and environmental applications

Over the past few years, single-atom catalysts (SACs) on the horizon have driven rapid and extensive scientific advances in heterogeneous catalysis. Nevertheless, large-scale applications of SACs in the environment have been hindered by the problematic synthesis of catalysts, because the atomic-scale materials with high activation energy are easy to form nanoclusters and nanoparticles in the synthesis stage. The catalytic stability and catalytic activity of SACs in the treatment of complex environmental pollutants also need to be further researched. Herein, the review is built on a comprehensive discussion of the design and synthesis strategies of SACs. The shortcomings of traditional methods and the improvement from different angles like defect regulation are analyzed. Furthermore, the reaction mechanism of SACs in different reactions was summarized, and the environmental applications of SACs, such as wastewater treatment, carbon dioxide reduction, nitrogen reduction, hydrogen evolution, NOx reduction and oxidation, volatile organic compounds removing and environmental monitoring are exemplified to deeply evaluate the prospects and challenges of SACs in the field of environmental protection.