Solar-driven thermo-photocatalytic CO2 methanation over a structured RuO2:TiO2/SBA-15 nanocomposite at low temperature

Abstract

A new hybrid catalyst composed of mesostructured silica SBA-15 functionalized with TiO2 and further loaded with RuO2 was developed to efficiently promote thermo-photocatalytic CO2 hydrogenation into methane at low temperatures. The catalytic activity was assessed with respect to TiO2:RuO2 loading, catalyst dosage, illumination source (polychromatic sunlight and monochromatic LEDs) and power, [H2]:[CO2] molar ratio, temperature, and catalyst reusability. The best methanation yields were attained for the RuO2(6.4%):TiO2(16.9%)/SBA-15 nanocomposite at 150 ºC, under simulated sunlight (0.21 W) and stoichiometric [H2]:[CO2] molar ratio, reaching: a specific CH4 production rate of 13.6 mmol gcat-1 h-1; 99.8 % selectivity; 96.8 % CO2 conversion (110-min; 40 mL); and apparent photonic efficiency/quantum yield of 39.5 %/42.1 %. Considering only the active RuO2:TiO2 photocatalyst mass (23.3 %), the CH4 production rate increased to 58.6 mmol gactive_cat-1 h-1. Besides, this highly-active photocatalyst featured excellent UV-Vis-IR light absorbance, high surface area, and stability for reuse when moist gas was removed between cycles.