To understand reaction kinetics in photocatalytic CO2 reduction, a continuous-flow mode of operation under high-purity reaction conditions is established for the first time. No sacrificial reagents are used. It is possible to follow the temporal evolution of CH4 (the only product detected under those conditions) as function of CO2 concentration or irradiation intensity. “Steady-state” CH4 production can be reached within ~3 hours, but formation of O2 is not detected in up to ~8 hours of reaction. On the contrary, if O2 is dosed, CH4 formation is entirely suppressed. Higher light intensity increases CH4 yields only up to a certain point. At high intensities, CH4 formation is independent of irradiation intensity. Our studies suggest that on TiO2 as photocatalyst either the amount of catalytic active sites or of excited charge carriers reaching the surface limit the yields. Instead of trying to liberate the byproduct O2, cyclic operation (reaction-regeneration) may be beneficial to increase CH4 yields.

Towards evaluating reaction kinetics in photocatalytic CO2 reduction: Influence of CO2 partial pressure and light intensity

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.