Single-atom photocatalysis: A new frontier toward solar energy conversion

Photocatalysis represents an emerging technology for solving the deteriorating energy crisis and environmental problems by directly harvesting green, renewable, and sustainable solar energy. Due to the maximum atomic utilization efficiency, tunable electronic structures and outstanding catalytic activities, single-atom catalysts (SACs) have emerged as promising candidates for photocatalysis. Although many reviews on single-atom photocatalysis have been reported in the past few years, a comprehensive review devoted to specifically elucidating the generic characteristics of SACs in heterogeneous photocatalysis has so far not yet appeared. In this review, we summarize the latest progress in SACs mediated photocatalysis paired with diverse photocatalytic mechanisms from a fresh insight. Firstly, we elucidate the various synthetic strategies for SACs with a focus on the advantages and disadvantages of each approach. Subsequently, state-of-the-art characterization methods utilized for unleashing the fine structures of single-atom photocatalysts have been concisely overviewed. Furthermore, widespread applications of SACs in diverse photocatalytic redox reactions are comprehensively introduced. Finally, the remaining challenges and future opportunities in this booming research field are outlooked for guiding the rational design of robust, stable, and high-performance SACs. Our review could inspire sparkling ideas on how to smartly utilize single atoms for crafting high-efficiency artificial photosystems towards solar energy conversion.