Insights into Mechanisms of Reverse Water Gas Shift Activity Enhancement over Reverse Microemulsion-Synthesized CuCeO2

Abstract

Copper-doped ceria (CuCeO₂) catalysts with 0–26.5 Cu/(Cu+Ce) at% were synthesized via the reverse microemulsion method. X-ray diffraction analysis of freshly synthesized and spent (post-reaction) catalysts showed no separate phase of copper or copper oxide, indicating that Cu was incorporated into the CeO₂ lattice, replacing Ce. Temperature programmed desorption experiments showed that the activation energy of CO₂ desorption increased for higher Cu loadings, indicating stronger CO₂ adsorption. This phenomenon was attributed to enhanced formation of oxygen vacancies due to Cu doping. X-ray photoelectron spectroscopy further confirmed the enhanced generation of oxygen vacancies due to Cu incorporation. Catalytic performance evaluation with the H₂/CO₂ feed in the 300–600 °C range showed that all catalysts were 100 % selective to CO generation, with higher Cu loadings resulting in CO₂ conversion close to equilibrium values at 500–600 °C. The activation energy of the reaction, determined through reaction tests, exhibited inverse relationship with the activation energy of CO₂ desorption. The relationship between these two energy barriers is explored, providing valuable insights into the mechanism of RWGS activity enhancement.