Theoretical study of the promotional effect of ZrO2 on In2O3 catalyzed methanol synthesis from CO2 hydrogenation

Methanol synthesis from CO2 hydrogenation on the ZrO2 doped In2O3 (110) surface (Zr-In2O3 (110)) with oxygen vacancy has been studied using the density functional theory calculations. The calculated results show that the doped ZrO2 species prohibits the excessive formation of oxygen vacancies and dissociation of H-2 on In(2)O(3 )surface slightly, but enhances the adsorption of CO2 on both perfect and defective Zr-In2O3 (110) surface. Methanol is formed via the HCOO route. The hydrogenation of CO2 to HCOO is both energetically and kinetically facile. The HCOO hydrogenates to polydentate H2CO (p-H2CO) species with an activation barrier of 0.75 eV. H3CO is produced from the hydrogenation of monodentate H2CO (mono-H2CO), transformation from p-H2CO with 0.82 eV reaction energy, with no barrier whether there is hydroxyl group between the mono-H2CO and the neighboring hydride or not. Methanol is the product of H3CO protonation with 0.75 eV barrier. The dissociation and protonation of CO2 are both energetically and kinetically prohibited on Zr-In2O3 (110) surface. The doped ZrO2 species can further enhance the adsorption of all the intermediates involved in CO2 hydrogenation to methanol, activate the adsorbed CO2 and H2CO, and stabilize the HCOO, H2CO and H3CO, especially prohibit the dissociation of H2CO or the reaction of H2CO with neighboring hydride to form HCOO and gas phase H-2. All these effects make the ZrO2 supported In2O3 catalyst exhibit higher activity and selectivity on methanol synthesis from CO2 hydrogenation. (C) 2017 Elsevier B.V. All rights reserved.