Recent advances in single-atom catalysts for electrochemical water splitting

Abstract

Electrochemical splitting of water is considered the most promising strategy to produce green hydrogen fuel. However, its wide applications are restricted by the slow electrochemical reactions taking place at the cathode and the anode, namely, the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), respectively. In recent years, the downsizing of conventional nanoparticle catalysts to single-atom species and the construction of single-atom catalysts (SACs) have been rapidly expanding research approaches to improve the sluggish kinetics of these two reactions. These SACs can possess high abilities to bridge the gap between homogeneous and heterogeneous catalysis. Herein, in celebration of the 13th anniversary of the emergence of the term single-atom catalysts, we present a brief discussion focusing on the recent developments in SACs for HER/OER applications. The innovative synthesis strategies, in-depth understanding of characterization methods and the subsequent evolution of the SAC classes depending on the type of substrates through the structure–activity relationship, i.e., alloy-based SACs, carbonaceous materials-based SACs and SACs anchored on other materials, are discussed. Finally, the current problems and challenges of some critical issues in SACs and the future directions for the developments in this field for electrochemical water splitting are also addressed.