A DFT study on surface dependence of β-Ga2O 3 for CO 2 hydrogenation to CH 3OH.

In this paper, the catalytic activities of various β-Ga2O3 surfaces for CO2 hydrogenation have been studied by density functional theory (DFT) calculations. The surface dependence of adsorptions and coadsorptions of reactants are investigated on two terminations of Ga2O3, which are Ga2O3(001) and Ga2O3(111). The active termination of Ga2O3(001) is identified and a surface structure rearrangement is determined. The thermodynamic profiles of surface intermediates involved in the reaction pathways for methanol formation are systematically calculated, and the initial key step of CO2 hydrogenation to bicarbonate is analyzed in detail. It has been found that the active Ga2O3(001) termination gives rise to a lower hydrogenation barrier largely due to the fact that saturated lattice O at Ga2O3(001) can act as a favorable site for both hydrogen adsorption and transfer while the unsaturated O at Ga2O3(111) is much less effective for these processes.