Using a high purity gas-phase photoreactor, fundamental studies of CO2 reduction were performed on TiO2-based materials. Even on the thoroughly studied crystalline TiO2, the mechanism of the reaction has not yet been clarified. We were able to clearly rule out CO and methanol as reaction intermediates on the way to methane: While CO behaves towards the catalyst as an inert gas and is not converted at all, methanol is preferentially reoxidized back to CO2 instead of being hydrogenated further to methane. Instead, our results support a reaction mechanism running over a C2-Intermediate, likely acetic acid or acetaldehyde, which also explains that ethane is always found as byproduct. Modifying the titanium dioxide with gold nanoparticles does not lead to an increase in methane formation. Instead, in presence of gold, hydrogen evolution from water splitting becomes the dominant reaction pathway.

Identification and exclusion of reaction intermediates in photocatalytic CO2 reduction to methane

251st National Meeting (2016)

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