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Oxidation of volatile organic compounds (VOC) and preferential oxidation of CO in the excess of H 2 (CO-PROX) were investigated over mono and bimetallic Au-Ag/CeO 2 and Au-Cu/CeO 2 catalysts. For the oxidation of VOC (2-propanol, ethanol and toluene) Au/CeO 2 was the most active catalyst for the combustion of alcohols to CO 2 , Ag/CeO 2 gave the best performance in the toluene total oxidation, Au-Ag/CeO 2 and Au-Cu/CeO 2 showed the highest selectivity to partial oxidation products. For CO-PROX Au-Ag/CeO 2 and Au-Cu/CeO 2 samples exhibited higher CO 2 yield at low temperature than monometallic ones. The improved performance of bimetallic catalysts were accounted for an enhancement of surface ceria oxygens mobility caused by the addition of Ag or Cu to Au/ CeO 2 and involved in both investigated reactions. This effect was more evident on Au-Ag/CeO 2 where a strong Au-Ag interaction occurred with formation of Au-Ag alloy or linked monometallic nanoparticles. Graphical Abstract

Photocatalytic water splitting for H 2 production and photocatalytic oxidation of 2-propanol, an example of volatile organic compounds, were investigated over TiO 2 catalysts loaded with gold and/or ceria. In the water splitting reaction the presence of gold only slightly affected the performance of TiO 2 whereas the presence of CeO 2 had a more remarkable positive effect. In the 2-propanol oxidation Au/TiO 2 was the most active sample in terms of alcohol conversion whereas Au/TiO 2 -CeO 2 exhibited the highest CO 2 yield. On the basis of characterization experiments (X-Ray Diffraction (XRD), Energy Dispersive X-ray Analysis EDX, surface area measurements, Diffuse Reflectance Spectroscopy (DRS) and Raman spectroscopy), it was suggested that the interaction of Au with TiO 2 causes an increase in the charge separation between the photo-excited electron/hole pairs, leading to an enhanced photocatalytic activity (to acetone over Au/TiO 2 and to CO 2 over Au/TiO 2 -CeO 2 ), whereas the presence of ceria, acting as a hole trap, positively mainly affects the formation of hydrogen by water splitting.

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