Implication of the role of oxygen anions and oxygen vacancies for methanol decomposition over zirconia supported copper catalysts

The interaction of methanol with Cu, monoclinic ZrO2, and Cu/m-ZrO2 catalysts has been investigated by temperature programmed desorption (TPD) and reaction (TPRS) with the aim of understanding the nature of the surface sites and the mechanism involved in methanol decomposition. A synergetic effect has been detected since the combination of copper and ZrO2 significantly facilitates the methanol decomposition with the facile evolution of H2 and CO species at much lower desorption temperature. In conjunction with DRIFTS and H2-TPD measurements of the Cu/ZrO2 sample reduced at elevated temperatures, methanol decomposition over Cu/ZrO2 is suggested to occur primarily on ZrO2 with the aid of the presence of oxygen anions and oxygen vacancies generated by species-spillover between copper and zirconia. The interface between copper and zirconia is also evidenced to be crucial to the decomposition of methanol, with the main role of metallic Cu being to provide sites for H2 removal by efficiently recombining the hydrogen atoms formed during the dehydrogenation of species located on zirconia.