Single-atom catalysts for high-efficiency photocatalytic and photoelectrochemical water splitting: distinctive roles, unique fabrication methods and specific design strategies

Hydrogen is regarded as one of the most promising energy carriers because of its renewable and clean nature. Among various routes to generate hydrogen, solar water splitting has received increasing interest due to the abundance of renewable and sustainable solar energy. Thus, it is crucial to rationally design and develop high-performance photocatalysts and photoelectrodes for achieving high-efficiency photocatalytic and photoelectrochemical water splitting, respectively. Single-atom catalysts (SACs) with well-distributed atoms anchored on substrates have attracted rapidly increasing attention in photocatalytic/photoelectrochemical water splitting because of the high activity, superior durability and extremely high atom utilization efficiency (100%). Herein, a timely and comprehensive review about the recent advances of SACs for photocatalytic and photoelectrochemical water splitting is presented by highlighting the distinctive and promotional roles of SACs in photo(electro)catalysis and unique fabrication methods for SACs used in this emerging field. Furthermore, several specific design strategies to boost the photo(electro)catalytic activity of SACs including substrate engineering, defect engineering, electronic structure modulation, constructing strong interactions, band gap/structure engineering, and transfer channel design are also presented and discussed. Finally, some perspectives on the development and design of SACs for high-efficiency solar energy utilization in future applications are provided by presenting the promises, critical issues and challenges.