Review of Nanocatalysts Comprising Single Atoms and Nanoparticles for Electrochemical Water Splitting

Electrochemical water splitting has been widely recognized as a highly promising and sustainable approach for large-scale green hydrogen production. However, the traditional water electrolysis process is hindered by the sluggish kinetics of cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER), and its widespread application is highly dependent on the development of efficient and robust catalysts. Recently, nanocatalysts composed of both single atoms and nanoparticles have emerged as a research frontier in the field of heterogeneous catalysis, which can not only preserve the advantages of conventional single-atom catalysts but also overcome their inherent limitations. Evidently, through the complementarity and synergy of different functional sites, these integrated catalysts can offer more opportunities for electrochemical water splitting. In this context, this review first describes their structural advantages as heterogeneous catalysts and various synthetic strategies. Subsequently, their representative applications in electrochemical cathodic HER, anodic OER, and overall water splitting are systematically summarized and discussed. Finally, the current challenges and potential future development prospects of these integrated catalysts for water electrolysis are further addressed. It is expected that this review will provide valuable perspectives for the fabrication and optimization of advanced catalysts for electrochemical water splitting.