Engineering Interfacial Oxygen Vacancies of Zn–Cr Sites for CO2 Activation and Hydrogenation

Abstract

Understanding the influence of oxygen vacancies is of great significance for revealing molecular adsorption and rational catalyst design. However, for the catalysts with multiple phases, the properties and intrinsic catalytic mechanism of oxygen vacancies on varied active sites have not been studied thoroughly. Herein, Zn–Cr catalysts with different oxygen vacancy distributions and contents are synthesized by engineering interfacial oxygen vacancies for CO₂ hydrogenation. Characterization and DFT calculations illustrate that although the oxygen vacancies are not prone to being generated on the monointerface between ZnO and ZnCr₂O₄ compared with the spinel or metal oxide phases, the ZnO/ZnCr₂O₄–O_v interfacial oxygen vacancy sites reduce the energy barriers of crucial HCOO* and H₃CO* intermediate formation for CH₃OH synthesis. With the assistance of the well-dispersed interface oxygen vacancies, 3Zn1Cr displays the highest methanol selectivity (80.5%) as well as the highest CO₂ conversion (19.2%) among all of the ratios of Zn–Cr catalysts. After further combination of 3Zn1Cr with modified β zeolite, the composite catalyst showed a superior liquefied petroleum gas selectivity of 84.0% at a CO₂ conversion of 30.2%. The proposed strategy here sheds light on the efficient composite catalyst design via a methanol-mediated route for C1 chemistry.