Influence of photodeposited gold nanoparticles on the photocatalytic activity of titanate species in the reduction of CO₂ to hydrocarbons

Photodeposition of Au nanoparticles was found to enhance the rate of photocatalytic CO₂ reduction to short hydrocarbons over titanate species in SBA-15. Product formation from contaminants was ruled out experimentally by a thorough pre-cleaning of the samples and the leak-tight design of the fully metal-sealed gas-phase photoreactor. Without Au, an active carbon pool was observed to accumulate on the catalyst, and higher hydrocarbons were formed. Infrared spectroscopy was used to identify formaldehyde/ paraformaldehyde as major compounds of the carbon pool. The results obtained in the absence of gas-phase water indicate that adsorbed water in the mesopores is sufficient to achieve CO₂ reduction and convert CO₂ mainly to methane. These results contribute to the knowledge-based improvement of photocatalysts for CO₂ reduction.