Coverage effect of surface oxygen vacancy on In2O3-catalyzed CO2 hydrogenation revealed by first principles-based microkinetic simulations

Density functional theory (DFT) calculations and microkinetic simulations were performed to study the effect of the surface oxygen vacancy (OV) coverage on the In2O3 catalyst for methanol synthesis from CO2 hydrogenation, focusing on the In2O3(110) surface with a high OV coverage of 1 ML (In2O3(110)-allov) and compared with that with a low OV coverage of <0.1 ML (In2O3(110)-vac). We find that the In2O3(110)-allov surface is less favorable for CO2 and H2 adsorptions than the In2O3(110)-vac surface, but the former has lower energy barriers for both the HCOO and COOH routes than the latter. Furthermore, the high OV coverage for the In2O3(110)-allov surface results in a significant lower CO2 reactivity, but gives surprisingly higher CH3OH selectivity. Our simulations may explain the experimentally observed deactivation of the In2O3 catalyst when over-reduced towards metallic In. Physical insights from this work should contribute to the rational design of efficient oxide-based CO2 hydrogenation catalysts.