Effect of Au surface plasmon nanoparticles on the selective CO2 photoreduction to CH4

• Deposition of small Au NPs quantitatively enhances the photoreduction under UV light of CO2 to C1 and C2 hydrocarbons.
• The increase in CH4 production is more than 12 times higher than for bare TiO2.
• This enhancement has been addressed to a decrease of the charge recombination rates due to the electron scavenging ability of Au NPs.
• Under visible light, Au/TiO2 catalyst shows photoactivity towards H2, CO and CH4 formation.

Various gold-supported TiO2 catalysts (0.5–3.0 wt.%) were prepared by a deposition–precipitation method, and their photocatalytic activity towards CO2 reduction was tested in the gas phase while using H2O as electron donor and UV and visible light as energy sources. CO and H2 are detected as major products in bare TiO2. However, the deposition of small Au nanoparticles (NPs) onto TiO2 was found to quantitatively enhance the reduction of CO2 mainly to methane and C2+ hydrocarbons. Transient absorption spectroscopy was used to correlate the improved CH4 production with an increased charge separation due to the electron transfer between the TiO2 and Au NPs. The amount of Au loaded onto TiO2 was optimized, with 1.0 wt.% showing the highest photocatalytic activity under UV light. Under visible irradiation, H2 and CH4 were identified as the main products, although showing significantly lower productions.

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