Mechanism and sites requirement for CO hydrogenation to CH3OH over Cu/CeO2 catalysts

Abstract

This study investigated the Cu-CeO2 interactions for CO hydrogenation to methanol by applying rate measurements, chemical titration/desorption, together with in-situ/operando spectroscopy techniques under realistic reaction conditions. Ce components were enriched in the surface region of Cu/CeO2 catalysts while Ce3+ and Ce4+ atoms co-existed during CO hydrogenation. The ratio of Ce3+ to Cu0 in the surface region of catalysts increased linearly with the Ce content. The turnover rates of CH3OH formation increased as a single-valued function of the ratio, irrespective to the individual contact extent between Cu and CeO2 clusters or Ce content in the Cu/CeO2 catalysts, indicating that the Cu0-Ce3+ sites pair acts as active sites for CO hydrogenation to methanol over Ce-CeO2 samples. This study also unraveled that formyl and formate species, as reactive surface intermediates, were co-adsorbed on the Cu0-Ce3+ sites, and their hydrogenation routes occurred concurrently for CH3OH formation during CO-H2 reactions.