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

Abstract

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.