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

Partial oxidation of methanol is a promising reaction for on-board production of high purity H-2 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 H-2 selectivity and the metallic copper (Cu degrees) 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 O-2 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 H-2 production for use in fuel cells or other clean energy applications.