Single-atom photocatalysts for CO2 reduction: Charge transfer and adsorption-activation mechanism

Photocatalytic CO₂ reduction is mainly inspired by natural photosynthesis, which could convert CO₂ into high value-added fuels or chemicals through the role of catalysts. However, the photocatalysis efficiency of the currently developed catalysts is far from meeting the actual needs due to the low efficiency of charge separation and energy transfer, and the poor adsorption and activation of CO₂ by catalyst surface. Single-atom catalysts (SACS) show an excellent activity, selectivity and stability in many important reactions, and exhibit great potential in photocatalytic reduction of CO₂ owing to their high atomic utilization and controllability of active sites. In the current review, recent progresses and challenges on SACs for photocatalytic CO₂ conversion systems are presented. The key fundamental principles and reaction mechanisms focusing on charge separation/transfer and molecular adsorption/activation on single-atom photocatalysts for CO₂ reduction are systemically explored. We outlined how single-atom active sites promote the photogenerated carriers separation/transfer and enhance molecular photoactivation. Besides, we put forward some challenges and prospects for the future development of single-atom photocatalysts in CO₂ reduction.