Ga and Zn Atom-Doped CuAl2O4(111) Surface-Catalyzed CO2 Conversion to Dimethyl Ether: Importance of Acidic Sites

Abstract

Reduction of CO2 to high-value oxygenates is a desirable technique to store alternative renewable energy. In this regard, CO2 reduction to dimethyl ether (DME) utilizing bifunctional catalysts is important. Using density functional theory calculations, we have modeled the CuAl2O4(111) surface for CO2 conversion to DME and also checked the importance of dopants (Ga and Zn) in tuning the active center of the catalyst. The plausible reaction mechanism as well as free energy changes for both the steps, CO2 conversion to methanol, followed by dehydration of methanol to DME, has been determined. From the studies, the role of Ga in modifying the acidic site of the CuAl2O4(111) surface that directly facilitates methanol conversion to DME is highlighted. The synergistic effect of Ga and Cu atoms by changing the mode of intermediate adsorption is also noted for the efficient conversion of CO2 to DME. The activity of the catalyst in the presence of H2O has also been checked. Overall, this work signifies the importance of moderate acidic sites in improving the activity of the catalyst toward direct conversion of CO2 to DME.