Role of WO3 loading in the hydrogenation of CO2 to methanol by CeO2-ZrO2-WO3 supported Cu-based catalysts: Experimental and DFT studies

This study investigates the influence of varying concentrations of tungsten trioxide (WO3) on its role as either a supportive material or an active component within copper (Cu) catalysts that are anchored on a cerium dioxidezirconium dioxide (CeO2-ZrO2-WO3) framework. The focus is on the catalytic process of hydrogenating carbon dioxide (CO2) to produce methanol. Both experimental methodologies and theoretical analyses were employed to gain a comprehensive understanding of how WO3 loading impacts the catalytic efficiency and overall performance of these Cu catalysts in the hydrogenation reaction. The results show the low loading of the WO3 to the support improves the activity of the catalyst, while the impregnation of WO3 on the W-free CeO2-ZrO2 support weakens the catalyst activity in the hydrogenating carbon dioxide. Density functional theory (DFT) calculations revealed that the incorporation of tungsten (W) onto the copper (Cu) (111) surface enhances the adsorption energies of the intermediates. This increase in adsorption energy corresponds to a rise in both the activation energy and the enthalpy of the reaction. Consequently, the overall reaction kinetics are hindered, indicating a diminished catalytic efficiency which confirms the experimental results. The results suggest that the formation of a copper-tungsten (Cu-W) alloy within Cu-based catalysts adversely affects the catalyst's efficacy during the hydrogenation of carbon dioxide. This decline in performance can be attributed to elevated activation energy barriers, which hinder the generation of key intermediates such as hydrocarboxyl (COOH) and formate (HCOO).