(569eg) A DFT Study of CO2 and H2 Adsorption on Doped and Undoped In2O3 Catalysts for CO2 Hydrogenation to Methanol

Renewable energy-driven methanol synthesis from CO₂ and green hydrogen is a viable and key process in both "methanol economy" and "liquid sunshine" visions. In₂O₃-based catalysts have recently shown promise for methanol production. (104) surface of hexagonal In₂O₃ exhibited the highest activity and methanol selectivity in previous studies. This study focuses on CO₂ and H₂ adsorption on doped and undoped In₂O₃ catalysts with (104) hexagonal surface with oxygen vacancy. Slab surfaces are investigated by means of spin-polarized periodic density functional theory calculations using the Vienna Ab-initio Simulation Package (VASP) with the projector-augmented wave (PAW) method. CO₂ is physically adsorbed on a vacant site with an -0.13 eV adsorption energy in agreement with previous works. A single hydrogen molecule can adsorb on CO₂-physisorbed In₂O₃ dissociatively. Similar to undoped In₂O₃, holmium doped In₂O₃ surface also exhibits physisorption of CO₂ on a vacant site with a relatively lower adsorption energy of -0.44 eV. With the dissociative adsorption of single hydrogen molecule, CO₂ molecule turns to CO. On the other hand, CO₂ molecule chemisorbs on gallium doped In₂O₃ as carbonate molecule with very small adsorption energy to be -1.06 eV. A single H₂ molecule dissociatively adsorbs on the surface with carbonate structure and carbonate structure turns to formate by the interaction of CO₂ and the H atom of hydrogen molecule. It is observed that gallium is a promising dopant for CO₂ hyrogenation to methanol.