Reactants-Driven Surface-Active Sites on a Cu/CeO2 Catalyst for Methanol Synthesis from Syngas

Graphical The apparent rate coefficients for CH 3 OH synthesis from CO hydrogenation are a single-valued function of the CO 2 -to-CO ratio in the contacting gas phase, because this ratio determines the extent of surface oxidation of Ce 2 O 3 to CeO 2 , the relative abundance of surface Ce 3+ , and in turn the density of Cu 0 -Ce 3+ sites pair on the working Cu/CeO 2 catalyst. This study investigated the dynamic structure of a working Cu/CeO 2 catalyst and its catalytic consequences for CH 3 OH synthesis via CO hydrogenation by kinetics, high-precise chemical titration, and a series of in situ X-ray spectroscopies. We have revealed that the apparent rate coefficients for CH 3 OH synthesis from CO hydrogenation are a single-valued function of the CO 2 -to-CO ratio in the contacting gas phase. This ratio determines the extent of surface oxidation of Ce 2 O 3 to CeO 2 , the relative abundance of surface Ce 3+ and Ce 4+ sites, and in turn, the density of Cu 0 -Ce 3+ sites pair on the working Cu/CeO 2 catalyst, although the chemical state of Cu and elemental distribution of both Cu and Ce were insensitive to the ratio. The reactivity of CH 3 OH formation and the Cu 0 -Ce 3+ sites decrease monotonously with an increase in the CO 2 -to-CO ratio. The direct connection of the reactivity and the oxidant-to-reductant ratio appears to be general for heterogeneous catalysis, for which the oxidant oxidizes metal atoms. In contrast, the reductant scavenges surface oxygen atoms, thus dictating the density of surface sites and their thermodynamic activities.