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

Abstract

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 μmol 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 H2, 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 H2, CO2, and CO, finally resulting in a significant enhancement of the photothermocatalytic activity for CH4 production. By concentrating the low-intensity light (120 mW/cm2) 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.