Redox-driven CO2-to-CO conversion over Ni/CeO2 catalysts: role of oxygen vacancies and weakened metal-support interaction

The methanation side reaction significantly limits CO selectivity in Ni-based catalysts for the reverse water-gas shift (RWGS) reaction, despite their high CO 2 conversion. To enhance CO selectivity and catalytic stability, this study modulated the metal-support interaction (MSI) by controlling CeO 2 particle size and evaluated its impact on CO selectivity. A series of Ni/CeO 2 -C catalysts was synthesized via a conventional hydrothermal-impregnation method. Precursor CeO 2 supports were calcined at different temperatures (500–1000 °C) to precisely control their particle size and morphology. Results demonstrate that the 5Ni/CeO 2 -C-1000 catalyst, derived from the support calcined at 1000 °C, delivered optimal performance: achieving a CO formation rate of 320.1 μmol min −1 at 600 °C and maintaining <5 % decay in CO 2 conversion after 50 h of reaction. Combined N 2 adsorption isotherms (BET) and X-ray photoelectron spectroscopy (XPS) analyses revealed that high-temperature calcination induced abundant oxygen vacancies and facilitated the partial reduction of Ni 2+ to Ni 0 , thereby weakening the MSI. Density functional theory (DFT) calculations further elucidated that the reaction follows a redox mechanism on this catalyst. The material surface exhibits strong CO 2 adsorption capability and a low energy barrier for CO 2 dissociation. Concurrently, its weak CO adsorption affinity effectively suppresses over-hydrogenation, ensuring rapid CO desorption and high selectivity. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) confirmed poor H 2 dissociation on this catalyst, along with the direct dissociation of CO 2 to CO followed by desorption. Collectively, these findings provide new theoretical insights into the relationship between weak MSI and the selective regulation of CO 2 hydrogenation products. Here, we prepared tunable Ni/CeO 2 catalysts for the reverse water-gas shift (RWGS) reaction, investigating the effects of metal-support interactions (MSI) on catalytic performance. The results show that high-temperature calcination (1000 °C) generated abundant oxygen vacancies (O v ) on CeO 2 surfaces, leading to a consequent weakening of the MSI. This synergistically enhanced CO 2 adsorption while suppressing CO adsorption energy, thereby achieving near-unity CO selectivity and exceptional cycling stability (>95 % activity retention after 30 h) in the RWGS reaction. • Elevated temperatures induced oxygen vacancy generation and partial Ni reduction, thereby weakening MSI. • Weak CO adsorption on 5Ni/CeO 2 -C-1000 facilitates rapid CO desorption. • During RWGS at 600 °C, the 5Ni/CeO 2 -C-1000 catalyst achieved 95.15 % CO selectivity with stable activity over 30 h.