Investigation of reaction condition effects on photocatalytic methane production over P25‐TiO2/Pt with CO2 and H2O gas. Applied and mechanistic implications

Abstract

AbstractThe photocatalytic activity of P25 TiO2 with 0.36 % (w/w) Pt co‐catalyst towards the formation of methane, in the presence of CO2 and H2O vapor, is investigated in a flow photoreactor under varying reaction conditions of temperature, water molar fraction in the dosed gas and residence time. Within the range of parameters studied, H2O molar fraction is found to be the most sensitive parameter, and its increase leads to larger production rates as well as to a significant slow down of photocatalytic activity loss. This observed activation with water content is in contrast to the effect known in neat P25 and it occurs in a regime of very large adsorbed H2O to CO2 excess, and can be understood in the context of hole extraction being much slower than electron extraction. These results also constrain the possible interpretation of the nature of the photocatalyst deactivation processes.