Thermo-photo catalytic CO2 hydrogenation over Ru/TiO2

Abstract

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 °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 °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.