Dependence of H2 and CO2 selectivity on Cu oxidation state during partial oxidation of methanol on Cu/ZnO

Abstract Partial oxidation of methanol is a promising reaction for on-board production of high purity H2 streams for fuel cell applications. In the present work, the influence of Cu oxidation state on the selectivity of POM catalyzed by Cu/ZnO was investigated via the use of a microreactor and X-ray photoelectron spectroscopy. A strong correlation between H2 selectivity and the metallic copper (Cu°) content of the catalyst was observed, while, surprisingly, the CO2 selectivity was not significantly affected by the catalyst oxidation state. Instead, CO2 selectivity showed a strong correlation with O2 partial pressure, which could be explained by differences in the energy barriers between CO desorption and CO2 formation from CO* on Cu2O surfaces calculated via first-principles calculations. Our results indicate that maintaining metallic Cu catalyst during methanol oxidation could maximize H2 production for use in fuel cells or other clean energy applications.