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.