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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

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The thermocatalytic, photocatalytic and photothermo-catalytic oxidation of some volatile organic compounds (VOCs), 2-propanol, ethanol and toluene, was investigated over brookite TiO2-CeO2 composites. The multi-catalytic approach based on the synergistic effect between solar photocatalysis and thermocatalysis led to the considerable decrease in the conversion temperatures of the organic compounds. In particular, in the photothermo-catalytic runs, for the most active samples (TiO2-3 wt% CeO2 and TiO2-5 wt% CeO2), the temperature at which 90% of VOC conversion occurred was about 60 °C, 40 °C and 20 °C lower than in the thermocatalytic tests for 2-propanol, ethanol and toluene, respectively. Furthermore, the addition of cerium oxide to brookite TiO2 favored the total oxidation to CO2 already in the photocatalytic tests at room temperature. The presence of small amounts of cerium oxide allowed to obtain efficient brookite-based composites facilitating the space charge separation and increasing the lifetime of the photogenerated holes and electrons as confirmed by the characterization measurements. The possibility to concurrently utilize the photocatalytic properties of brookite and the redox properties of CeO2, both activated in the photothermal tests, is an attractive approach easily applicable to purify air from VOCs.

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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Brush-like ZnO nanorods shell grown by CBD onto electrospun PES fibres as photocatalytic membranes for water purification.

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