MOF-Templated Preparation of Highly Dispersed Co/Al2O3 Composite as the Photothermal Catalyst with High Solar-to-Fuel Efficiency for CO2 Methanation

摘要

CH4 production from CO2 hydrogenation provides a clean approach to convert greenhouse gas CO2 into chemical energy, but high energy consumption in this reaction still restrains its further application. Herein, we use a light-driven CO2 methanation process instead of traditional thermocatalysis by an electrical heating mode, with the aim of greatly decreasing the energy consumption. Under UV-vis-IR light irradiation, the photothermal CO2 methanation over highly dispersed Co nanoparticles supported on Al2O3 (Co/Al2O3) achieves impressive CH4 production rates (as high as 6036 mu mol g(-1) h(-1)), good CH4 selectivity (97.7%), and catalytic durability. The high light-harvesting property of the catalyst across the entire solar spectrum coupled with its strong adsorption capacity toward H-2, CO2, CO, and abundant active sites are proposed to be responsible for the better photothermocatalytic performance of Co/Al2O3. Furthermore, a novel light-promotion effect is also revealed in CO2 methanation, where UV-vis light irradiation induces oxygen vacancies and improves the proclivity toward adsorption of H-2, CO2, and CO, finally resulting in a significant enhancement of the photothermocatalytic activity for CH4 production. By concentrating the low-intensity light (120 mW/cm(2)) via a Fresnel lens, a photothermal CO2 conversion efficiency of more than 50% with a good CH4 selectivity (76%) is achieved on the optimal catalyst under a dynamic reaction system, which indicates the bright prospect of photothermal CO2 methanation.