Transition-Metal-Doped CeO₂ for the Reverse Water-Gas Shift Reaction: An Experimental and Theoretical Study on CO₂...

Transition metal-doped ceria (M-CeO₂) catalysts (M=Fe, Co, Ni and Cu) with multiple loadings were experimentally investigated for reverse water gas shift (RWGS) reaction. Density functional theory (DFT) calculations were performed to benchmark the properties that impact catalytic activity of CO₂ reduction. Temperature-programmed desorption (TPD) was conducted to study the CO₂ binding strength on doped CeO₂ surfaces; the trend of the energy along increasing metal loading agrees with the DFT calculations. Notably, CO₂ dissociative adsorption energy and oxygen vacancy (OV) formation energy are key descriptors obtained from both DFT and experiments, which can be used to evaluate catalytic performance. Results show the effectiveness of transition metal doping in enhancing CO₂ adsorption and reducibility of the surfaces, with Fe showing particularly promising results, i. e., CO₂ conversion higher than 56 % at 600 °C and 100 % selectivity to CO. Cu exhibits 100 % selectivity to CO but low CO₂ conversion, while Co and Ni showed notable ability of methanation, particularly at high loadings. This study finds that an effective CeO₂ based RWGS catalyst corresponds to OV sites that have low OV formation energies for surface reduction, and moderate CO₂ adsorption energies for strong interaction with the surface to promote C-O bond scission.