DFT-based microkinetic studies on methanol synthesis from CO2 hydrogenation over In2O3 and Zr-In2O3 catalysts.

Abstract

Density functional theory (DFT) calculations and microkinetic simulations were performed to study the structure-performance relationship of In2O3 and Zr-doped In2O3 catalysts for methanol synthesis, focusing on the In2O3(110) and Zr-doped In2O3(110) surfaces. These surfaces are expected to follow the oxygen vacancy-based mechanism via the HCOO route for CO2 hydronation to methanol. Our DFT calcualtions show that the Zr-In2O3(110) surface is more favorable for CO2 adsorption than the In2O3(110) surface, and although the energy barriers are not lowered, most intermediates in the HCOO route are stablized with the introduction of the Zr dopant. Microkinetic simulations suggest that the CH3OH formation rate is improved by ∼10 times and CH3OH selectivity increased significantly from 10% on In2O3(110) to 100% on the Zr1-In2O3(110) catalyst model at 550 K. We find that the higher CH3OH formation rate and CH3OH selectivity on the Zr1-In2O3(110) surface than those on the In2O3(110) surface can be attributed to the slightly increased OV formation energy and the stablization of the reaction intermediates, whereas the much lower CH3OH formation rate on the Zr3-In2O3(110) surface is due to the much higher OV formation energy and the over binding of the H2O at the OV site.