Tracking the critical roles of Cu+ and Cu0 sites and the optimal Cu+/Cu0 ratio for CH3OH steam reforming (MTSR) to manufacture H2

Abstract

Understanding the nature of surface-active sites is of critical importance for catalyst design, yet remains great challenges because of the complexity of solid surfaces. To tracking the valence states and roles of various Cu sites played in CH3OH steam reforming (MTSR) on Cu-based catalysts and the factors to determine the reactivity, appropriate Cu/Ce1-xZrxO2 solid solution catalysts have been purposely designed. On a catalyst having a Ce/Zr ratio of 0.7/0.3 (Cu/Ce0.7Zr0.3O2), the optimal Cu+/Cu0 ratio around 1.00 can be obtained to accomplish the best performance, with a high H2 production rate but very low CO selectivity. With the combination of experiments and DFT calculation, it has been discovered that CH3OH molecules mainly be adsorbed/activated on the Cu+ sites, but H2O molecules could mainly be adsorbed/activated on the Cu0 sites. We have substantiated that to fabricate Cu/Ce1-xZrxO2 catalysts with high efficiency, nearly equal amount of surface Cu+ and Cu0 sites should be engineered.