Unraveling the Surface Chemistry in Ni/La-Ceria Catalysts for the Reverse Water−Gas Shift Reaction

The reverse water–gas shift (RWGS) reaction is critical for efficient CO2 utilization in thermochemical conversion processes. Here, we investigate how lanthanum (La) doping modulates the redox properties of Ni/CeO2 catalysts and influences their RWGS performance. Using a combination of catalytic testing, operando diffuse reflectance infrared Fourier transform spectroscopy, and density functional theory calculations, we identify key surface intermediates and establish composition–activity relationships. CO2 initially adsorbs as bicarbonate species preferentially stabilized at oxygen vacancies, which subsequently convert to formates, the dominant intermediates under RWGS conditions. Methoxy and dioxymethylene species serve as spectroscopic markers for Ce4+ and Ce3+/oxygen vacancy sites, respectively. Notably, catalysts with intermediate La loading exhibit the highest CO selectivity due to an optimal balance between oxygen vacancy formation and redox flexibility. These results reveal a direct link between catalyst redox state and RWGS activity, underscoring the value of rational dopant design. La incorporation thus offers a viable strategy to enhance the performance of Ni/CeO2-based catalysts for CO2 conversion.