Single-atom catalysts for photocatalytic hydrogen evolution: A review

The application of hydrogen energy is significant to meet the challenge of fossil energy depletion and carbon emission limitation. The photocatalytic hydrogen evolution has been considered as a green and clean strategy for obtaining hydrogen. However, due to the high cost and limited efficiency, photocatalysis is only considered as one of the candidate methods for hydrogen production. Recently, several researchers have devoted to develop the single-atom catalysts (SACs) as promising cocatalysts and found great potential applications that are distributed across the fields of energy and environmental science. SACs exhibit several advantages, including abundant active sites, efficient photo-generated carrier recombination, atom-economic reaction mechanism, etc. In this synthetic review, we have summarized the advances of SACs in photocatalytic hydrogen evolution. Firstly, the synthesis strategies and characterization methods of SACs have been introduced. Then, the approaches for immobilizing prepared SACs on various supports have been elucidated. Finally, the photocatalytic activity of representative SACs-loaded supports has been analyzed, as well as the modification routes for enhancing performance. The review aims to record the development and applications of SACs in the field of photocatalytic hydrogen evolution. More studies are still required to clarify the mechanism of SACs based photocatalytic reactions, thus guiding the design of SACs-support system.