A comprehensive review on photo-thermal co-catalytic reduction of CO2 to value-added chemicals

Conversion of carbon dioxide (CO2) to value-added chemicals via solar energy input possesses great significance in industry for the synthesis of key chemical feedstocks and reduces emission of greenhouse gas. However, the current efficiency is still far from satisfying, especially suffering from high energy consumption and severe deactivation of the catalysts. To solve this problem, the photo-thermal co-catalytic has been widely used in CO2 reduction, because the introduction of light can effectively reduce the energy barrier of the thermal reaction, and provide milder reaction conditions. The synthesis of robust and low-cost photo-thermal catalysts are crucial for the CO2 conversion. Recently, the significant progress has been made in regulating the structure and composition of photo-thermal catalysts and understanding the photo-thermal co-catalytic mechanism and structure-activity relationship. In this review, we first introduce the fundamentals of photo-thermal co-catalysis and possible reaction pathways of CO2 hydrogenation. Subsequently, various photo-thermal catalysts for CO2 conversion are overviewed, including metal/metal oxides, metal/carbides, metal/nitrides, sulphides, phosphides, layered double hydroxides and its derivatives. Thereafter, photo-thermal co-catalysis processes for CO2 conversion are summarized, including CO2 hydrogenation to methane/methanol/carbon monoxide/C2+ hydrocarbons, CO2 reforming of CH4, CO2-assisted hydrocarbons (ethane/propane) dehydrogenation, and solar thermochemical splitting of CO2. Ultimately, we discuss the challenges and perspectives of photo-thermal reduction of CO2. The main purpose of this review is to provide some insights into photo-thermal catalysts design, and a deep understanding of mechanism of CO2 reduction, as well as giving an appreciation of application prospects for photothermal co-catalytic CO2 conversion technology.