(675d) Insights into the Structure-Activity Relationship of Cu-Doped Ceria for Reverse Water-Gas Shift Reaction: A Combined Theoretical and Experimental Investigation

Reverse water gas shift (RWGS) is a promising technology for producing syngas from CO₂. Although copper-doped ceria (Cu/CeO₂) is a potentially effective catalyst for RWGS, limited progress has been made in elucidating CO₂ adsorption and reaction mechanism and the relationship between the microstructure of the catalyst and its performance in RWGS. In this work, Cu/CeO₂ was synthesized using the reverse micro emulsion (RME) method and its performance was evaluated using density functional theory (DFT) calculations and various experimental techniques, including XRD, ICP, XPS, CO₂ TPD, and in situ FTIR. The catalytic performance of Cu/CeO₂, evaluated from 300 to 600 °C showed that all samples of Cu/CeO₂ were 100% selective to CO generation, with higher doping concentrations displaying conversion values significantly better than pure ceria at higher temperatures (500-600°C). Characterization results from the catalyst showed no distinct phase of copper or copper oxides, indicating that copper was atomically incorporated into ceria, and this was also confirmed using DFT based investigations. CO₂ adsorption energetics calculated from DFT and CO₂ TPD results show that the adsorption energy increases with the increase in the concentration of Cu. DFT calculations also reveal that Cu-doping enhances CO₂ reactivity by introducing oxygen vacancies, that ultimately lead to more under-coordinated surface atoms and active sites. Furthermore, reaction pathways determined from DFT and in situ FTIR, revealed consistent key reaction intermediates, i.e., carbonate and carboxylate, on both CeO₂ and Cu/CeO₂ surfaces, suggesting that the increase in the number of oxygen vacancies is mainly responsible for the superior catalytic activity. Overall, the combined theoretical and experimental study provides mechanistic insights into CO₂ activation and the role of copper doping in enhancing the activity of the RWGS reaction on ceria. These findings could serve as valuable guidelines for the development of highly active and selective RWGS catalysts.