Recent developments in the use of single-atom catalysts for water splitting

Electrochemical water splitting is regarded as the most promising approach to produce hydrogen. However, the sluggish electrochemical reactions occurring at the anode and cathode, namely, the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), respectively, consume a tremendous amount of energy, seriously hampering its wide application. Recently, single-atom catalysts (SACs) have been proposed to effectively enhance the kinetics of these two reactions. In this minireview, we focus on the recent progress in SACs for OER and HER applications. Three classes of SACs have been reviewed, i.e., alloy-based SACs, carbon-based SACs and SACs supported on other compounds. Different factors affecting the activities of SACs are also highlighted, including the inherent element property, the coordination environment, the geometric structure and the loading amount of metal atoms. Finally, we summarize the current problems and directions for future development in SACs.