Artificial leaf for light-driven CO2 reduction: Basic concepts, advanced structures and selective solar-to-chemical products

To date, the elevating atmospheric carbon dioxide (CO2) levels are becoming a global concern, which has promoted scientists to seek possible solutions for reducing CO2 emissions or capturing them. Solar light-assisted catalytic conversion of CO2 into valuable chemicals has been considered viable to mitigate the environmental and energy crisis simultaneously. In this regard, an artificial photosynthesis system, often called "artificial leaf" consisting of substantial structural components and reaction parameters of natural photosynthesis to attain solar light-driven CO2 conversion, is up-and-coming. Inspired by natural leaves, photocatalytic and photo-electrocatalytic artificial leaf structures that mimic natural photosynthesis and efficiently utilize solar energy to convert CO2 into value-added products are of great significance. This review focuses on the basic concepts of photo/electrocatalytic artificial leaf systems, emphasizing advanced structural arrangements and the mechanistic insights for CO2 reduction. The recent advances in the structural design of artificial leaves involving Z-scheme biocatalytic photoelectrochemical devices, photocatalytic prototype, and latest 3D printing has been extensively explored and discussed. The crucial applications of artificial leaf devices for the selective conversion of CO2 into carbon monoxide (CO), methane (CH4), and formate have been outlined. Finally, we conclude and provide a vision with an in-depth discussion on how the present state-of-the-art advances and various challenges in this field. We expect to believe this comprehensive study could stimulate more remarkable research efforts to design efficient artificial leaf for light-driven CO2 reduction towards selective solar-to-chemical products in the coming years.