Thermo-photo catalytic CO2 hydrogenation over Ru/TiO2

It is attractive to convert CO2 greenhouse gas into valuable compounds via photocatalysis with solar energy. One of the important processes is the photocatalytic hydrogenation of CO2. However, its current process still suffers from inefficiency. Herein, thermal energy was introduced to increase the driving force for photocatalysis, leading to efficient thermo-photo catalytic reduction of CO2 over a 1 wt% Ru/TiO2 catalyst in a fixed bed reactor. Even at a low temperature of 150 degrees C and 1 atm, a high yield of CH4 (1.72 mmol g(cat)(-1) h(-1)) under weak sunlight irradiation (1 sun) was achieved, whereas no CH4 was detected without light irradiation. It is two orders of magnitude larger than most reported results, and twice of the recently reported maximum value under strong sunlight (14.5 sun) irradiation. Furthermore, the CH4 yield increased to 69.49 mmol g(cat)(-1) h(-1) at 300 degrees C, which is 3 times larger than that without light irradiation. The limitation of room-temperature photocatalytic CO2 hydrogenation and the advancement of the thermo-photo process are further revealed in terms of thermodynamics and kinetics.