Structure–reactivity relationship in Co3O4 promoted Au/CeO2 catalysts for the CH3OH oxidation reaction revealed by in situ FTIR and operando EXAFS studies

A strong influence of the amount of the Co3O4 promoter on the catalytic performance in methanol oxidation of different gold catalysts supported on ceria was observed. The activity followed the order: Au/10 wt% Co3O4-doped CeO2 > Au/5 wt% Co3O4-doped CeO2 > Au/15 wt% Co3O4-doped CeO2 > Au/CeO2 ≫ Au/Co3O4. FTIR measurements of adsorbed CO indicate that oxidized gold sites are initially present on the activated samples and that such species are involved in the methanol reaction. Methanol oxidation performed under static conditions gave rise at 75 °C to mainly formate species on Au/CeO2 and to a large variety of different carbonate species on Au/10 wt% Co3O4-doped CeO2. FTIR and EXAFS analyses revealed that the active sites present on the best performing Au/CeO2 catalyst added with 10 wt% Co3O4 are oxidized gold species, close to Co sites, at the interface with the support, which are reduced under reaction conditions. These species are able to activate and to react with oxygen giving rise to formate and carbonate species.