Surface Probing by Spectroscopy on Titania-Supported Gold Nanoparticles for a Photoreductive Application

The continuous increase in scientific reports concerning photocatalysis and in particular CO 2 photoreduction in recent years reveals the high degree of interest around the topic. However, the adsorption and activation mechanisms of CO 2 on TiO 2 , the most used photocatalyst, are poorly understood and investigated. Gold nanoparticles were prepared by a modified deposition-precipitation method using urea and a chemical reductant. Bare P25 was used as reference. Combined spectroscopic investigations of fresh and spent samples with photoactivity studies reported in this article provide new insights to the role of CO 2 adsorption and carbonate formation on Au/TiO 2 during CO 2 photocatalytic reduction. The key intermediates’ and products’ adsorption (CO, methanol, ethanol) was studied, coupled with X-ray photoelectron microscopy (XPS) and UV-Visible spectroscopy. The adsorption of CO 2 on fresh and spent catalysts changes radically considering the carbonate formation and the gold surface presence. Methanol and ethanol revealed new adsorbed species on Au with respect to bare titania. The characterisation of the spent catalysts revealed the good stability of these samples.