Theoretical Insights into CO2 Activation and Reduction on the Ag(111) Monolayer Supported on a ZnO(000(1)under-bar) Substrate

First principles calculations are performed to investigate CO2 adsorption and reduction on Ag(111)/ZnO(000 (1) under bar) surfaces and interfaces. First, the pristine Ag(111) surface turns out to be quite noble for CO2 adsorption, as its d-band states are located well below the Fermi level. The d-band states of the Ag(111) surface are subject to a tensile strain slightly shifting toward the Fermi level. However, the d-band center is still far away from the Fermi level. A critical change of the d-band states is obtained when the stretched Ag(111) monolayer is supported on the ZnO(000 (1) under bar) substrate. The binding ability between the supported Ag(111) monolayer and CO2 molecule is an intermediate strength. Thus, the CO2 reduction in the subsequent hydrogenation process is optimized as well. Furthermore, we demonstrate that the stretched Ag(111) monolayer supported on the ZnO(000 (1) under bar) substrate is indeed stable under H-2-rich conditions. This surface can even maintain the improved ability for CO2 adsorption and reduction in the presence of Zn impurities.