Active copper structures in ZnO-Cu interfacial catalysis: CO₂ hydrogenation to methanol and reverse water-gas shift reactions

Cu-ZnO-based catalysts are widely used to catalyze the CO2 hydrogenation to methanol and reverse water-gas shift (RWGS) reactions. Herein, via a combined experimental and theoretical calculation study of various Cu nanocrystals (NCs) with welldefined Cu facets and corresponding ZnO/Cu NC inverse catalysts, we demonstrate the Cu{110} facets as the most active facet for ZnO-Cu interfacial catalysis in the CO2 hydrogenation to methanol with an apparent activation energy as low as 25.3 +/- 3 kJ mol(-1) and the Cu{100} facets as the most active facet for both ZnO-Cu interfacial catalysis and Cu catalysis in the RWGS reaction. Although the ZnO-Cu interface is more active in catalyzing the RWGS reaction than the Cu surface, the RWGS reaction occurs mainly on the bare Cu surface of ZnO/Cu inverse catalysts under the CO2 hydrogenation to methanol instead of that at the ZnO-Cu interface. This fundamental understanding will greatly help to fabricate efficient Cu-ZnO-based catalysts for the CO2 hydrogenation to methanol.