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

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 O_V 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 O_V formation energy and the over binding of the H₂O at the O_V site.