Exploring the phase transformation in ZnO/Cu(111) model catalysts in CO2 hydrogenation

Abstract Sustainable methanol production via CO2 hydrogenation leads to increased interest in the understanding of active phase of Cu/ZnO/Al2O3 (CZA) catalyst. Model catalysts of ZnO/Cu(111) with structures varied from two-dimensional planar to three-dimensional nanoparticles were prepared by atomic layer deposition (ALD) method. By combing scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) at near-ambient pressure of CO2 hydrogenation, we reveal that the submonolayer ZnO/Cu(111) transformed into Cu-Zn alloy under 10 mbar CO2/H2 at 493 K, and underwent a partial re-oxidation during evacuation. The dynamic phase transformation of ZnO/Cu(111) may partly explain the existence of differences and apparently contradictory theories to account for the origin of active phase in CZA catalysts.