Photocatalytic CO₂ reduction reaction: Influencing factors, reaction pathways and dominant catalysts

Photocatalytic reduction of CO2 technology has become one of the potential technologies for CO2 recycling due to advantages of mild reaction conditions, green and clean. Currently, photocatalytic CO2 reduction reaction (CO2RR) has limitations of low conversion rate and poor product selectivity. Therefore, the optimization of reaction process and the improvement of catalyst performance are the current research priorities. This review introduces the principle and process of photocatalytic CO2RR, summarizes the effects of the key influencing factors (photo-excitation, separation/transfer of photogenerated electron-hole pairs, adsorption/activation of CO2, etc.), possible adverse processes/competitive reactions (photo-corrosion, hydrogen evolution competition, product oxidation, etc.) and the types of reactors on catalytic performance, puts forward the corresponding optimization measures (element doping, defect engineering, co-catalyst loading, heterojunction structure etc.), and combs possible reaction pathways of carbene pathway and formaldehyde pathway from C-1 products (CH4, CO, CH3OH, etc.), and the coupling of CH2 or CH3 intermediate to ethylene (C2H4) or ethane (C2H6) based on C-1 pathway and glyoxal pathway of the formation of CH3COOH based on formyl dimerization in the photocatalytic CO2RR. Based on the above-mentioned reduction products, this review respectively summarizes the research progress of dominant catalysts (TiO2-, carbon nitride-, metal organic framework-, covalent organic framework-, Cu- and sulfide-based catalysts, etc.) and their catalytic performances, which provide the basis design and also advanced ideas for improving CO2RR catalysts with outstanding performance and selectivity.