Metallic single-atoms confined in carbon nanomaterials for the electrocatalysis of oxygen reduction, oxygen evolution, and hydrogen evolution reactions

Carbon nanomaterials confined with metallic single-atoms have shown great potential in electrocatalysis because of their unique physicochemical properties such as high-efficiency, high mass activity and maximum atom-utilization for reactions involved in electrochemical energy conversion and storage, such as oxygen reduction, oxygen evolution, and hydrogen evolution reactions. In principle, metal single-atoms dispersed on appropriate carbon support ideally possess tunable coordination environment and unique electronic properties that result in excellent activity and selectivity toward catalytic reactions as compared to nanoparticles/or bulk form of noble and non-noble metals. This article reviews the recent advances of metal single-atom confined carbon nanomaterials, following their rational design strategies and correlation between metal-support combinations for the electrocatalysis of oxygen reduction, oxygen evolution, and hydrogen evolution reactions, including bifunctional activities for metal-air batteries and water electrolysis. A perspective on emerging fields of single-atom catalysis is also provided in this study. (AU)