A combined experimental and DFT study of H2O effect on In2O3/ZrO2 catalyst for CO2 hydrogenation to methanol

Abstract

CO2 hydrogenation with renewable energy is one of the promising approaches to mitigate CO2 emissions and produce sustainable chemicals and fuels. The effect of adding H2O in the feed gas on the activity and selectivity of In2O3/ZrO2 catalysts for CO2 hydrogenation to methanol was studied using combined experimentatal and computational efforts. Notably, adding an appropriate amount of H2O (0.1 mol%) in the feed gas significantly enhanced the CH3OH formation (ca. 20%) with improved selectivity. Characterization with STEM/EDS and CO2-TPD confirmed the preservation of In-Zr strong interaction in the presence of additional H2O and H2O-induced oxygen vacancies, which significantly improved CO2 adsorption capacity. XPS analysis revealed the formation of InOOH species due to H2O addition, which appeared to correlate to H2O-dependant enhancement of CH3OH formation. Density functional theory calculations rationalized the effect of surface H2O on InOOH formation and its correlation to CH3OH synthesis activity. Adding H2O was found to facilitate surface InOOH formation, suppress CO formation through COOH* intermediate, and promote CH3OH formation via HCOO* intermediate. However, excess H2O addition resulted in aggregation of In species and reduction of surface In0 for H2 dissociation.