Strong Electronic Oxide–Support Interaction over In₂O₃/ZrO₂ for Highly Selective CO₂ Hydrogenation to Methanol

Abstract

Metal oxides are widely employed in heterogeneous catalysis, but it remains challenging to determine their exact structure and understand the reaction mechanisms at the molecular level due to their structural complexity, in particular for binary oxides. This paper describes the observation of the strong electronic interaction between In₂O₃ and monoclinic ZrO₂ (m-ZrO₂) by <i>quasi-in-situ</i> XPS experiments combined with theoretical studies, which leads to support-dependent methanol selectivity. In₂O₃/m-ZrO₂ exhibits methanol selectivity up to 84.6% with a CO₂ conversion of 12.1%. Moreover, at a wide range of temperatures, the methanol yield of In₂O₃/m-ZrO₂ is much higher than that of In₂O₃/t-ZrO₂ (t-: tetragonal), which is due to the high dispersion of the In-O-In structure over m-ZrO₂ as determined by <i>in situ</i> Raman spectra. The electron transfer from m-ZrO₂ to In₂O₃ is confirmed by XPS and DFT calculations and improves the electron density of In₂O₃, which promotes H₂ dissociation and hydrogenation of formate intermediates to methanol. The concept of the electronic interaction between an oxide and a support provides guidelines to develop hydrogenation catalysts.