Theoretical insights into the surface structure of In2O3(1 1 0) surface and its effect on methanol synthesis from CO2 hydrogenation

Abstract

The surface structure of In2O3(1 1 0) surface and its effect on methanol synthesis from CO2 hydrogenation via HCOO route have been studied using combined density functional theory calculations and the atomistic thermodynamics method. The thermal desorption of surface oxygen atoms on In2O3(1 1 0) surface are random and not affected by the adjacent vacancies. The temperature and components of gas atmosphere have pronounced effect on the structure of In2O3(1 1 0) surface while the effect of pressure is inapparent. Under actual methanol synthesis conditions, the surface structure of In2O3(1 1 0) surface is in the state of few surface oxygen atoms on the surface. The In2O3(1 1 0) surface under lower surface reduction degree is favorable for methanol synthesis since the excessively formed oxygen vacancies around the active site on the surface can prohibit the dissociation of molecule H2, hydrogenation of adsorbed CO2 and protonation of H3CO species, and is not facile for the stability of adsorbed CO2 and dissociatively adsorbed H2. The fundamental effect of the surface reduction degree is the transformation of the micro surface environment of the active site with the change of surface reduction degree of In2O3(1 1 0) surface. It is essential to maintain the balance between surface oxygen atoms and vacancies with a lower surface reduction degree on In2O3 surface to obtain a higher performance for methanol synthesis from CO2 hydrogenation.