Recent advance in single-atom catalysis

Single-atom catalysts (SACs) have obtained a great deal of attention in many catalytic fields due to the high atom utilization efficiency and high catalytic activity. Recently, great achievements on SACs have been made for thermocatalysis, electrocatalysis, and photocatalysis which play an important role in obtaining value-added products. However, it remains a great challenge to fabricate SACs with high metal loading and investigate their reaction mechanisms. Therefore, it is necessary to highlight the recent development of SACs in these fields to guide future research. In this review, we overviewed the thermocatalysis applications of SACs in CO oxidation, preferential oxidation of CO, water-gas shift reaction, methane conversion, methanol steam reforming, aqueous-phase reforming of methanol, hydrogenation of alkynes and dienes, hydrogenation of CO, and hydrogenation of substituted nitroarenes. Moreover, the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), oxygen evolution reaction (OER), CO2 reduction reaction (CO2RR), and N2 reduction reaction (N2RR) for photocatalytic and electrocatalytic fields were also overviewed. Lastly, the opportunities and challenges of SACs were pointed out.