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.