Enhanced In–Zr Composite through Zr Addition for Reverse Water–Gas Shift Reaction via Oxygen Vacancies

Indium oxide is widely applied in CO2 hydrogenation for its excellent performance. However, In2O3 undergoes rapid deactivation during hydrogenation processes. Here, In2O3–ZrO2 composites with different nIn:nZr mole ratios are synthesized by a deposition–precipitation method, followed by a 500 °C calcination process, and the CO2 hydrogenation performance in converting CO2 to CO has been investigated. XRD, BET, TEM, and H2-TPR analyses were carried out to explore the physicochemical properties of these In–Zr composite catalysts. CO2 performance results imply that combining In2O3 with ZrO2 significantly enhances the CO production rate. Among these In–Zr composite catalysts, the 7In3ZrOx composite catalysts exhibits the best CO2 conversion, achieving a 40% yield of CO. In contrast, an excessively high Zr content leads to extensive ZrO2 coverage on the surface, which diminishes the CO2 conversion activity. The introduction of Zr into the In–Zr composite catalyst facilitates oxygen vacancy formation, resulting in a significantly higher CO yield compared with pure In2O3 (ca. 6%). Oxygen vacancies on 7In3ZrOx enhance CO2 hydrogenation to generate CO under reaction conditions. Furthermore, Zr addition enhances the In–O–Zr interaction and improves the stability of the In–Zr composite in the RWGS reaction.