Progress in design and preparation of multi-atom catalysts for photocatalytic CO2 reduction

Photocatalytic CO2 reduction towards various fuels is of significant interest under the background of mitigating the global warming induced by CO2 emission and lowering the depletion of fossil fuels. However, state-of-the-art photocatalysts still suffer from sluggish reaction dynamics and frustrated product selectivity, especially for C2+ generations, which are of great interest for industrial applications. Over the past decades, comprehensive research on solar-driven CO2 reduction has consistently unveiled some encouraging results in meaningful pathways and architectural design of active sites over photocatalysts. This review highlights the recent advances in boosting photocatalytic CO2 reduction of atomically dispersed catalysts via engineered active sites, including two separated active sites, paired dual-active sites, and nanoclusters based on the configuration of active sites. Both the mechanism of CO2 activation over active sites and advanced characterization methods are discussed in detail. Particularly, in consideration of the wide gap between fundamental research and practical applications, the integrations of experimental and theoretical results are analyzed to realize the underlying structure-activity relationships as well as promising selectivity toward target products. Finally, the remaining challenges in the field are outlined, and inquisitive perspectives with a focus on the rational design of active sites and mechanistic investigation are proposed.