Identifying the roles of Ce3+-OH and Ce-H in the reverse water-gas shift reaction over highly active Ni-doped CeO2 catalyst

Nickel-CeO2-based materials are commonly used for the thermal catalytic hydrogenation of CO2. However, high Ni loadings and low CO selectivity restrict their use in the reverse water-gas shift (RWGS) reaction. Herein, we demonstrate a highly active, robust, and low-Ni-doped (1.1 wt.%) CeO2 catalyst (1.0-Ni-CeO2). The Ni-based-mass-specific CO formation rate reaches up to 1,542 mmol.g(Ni)(-1).h(-1) with 100% CO selectivity at 300 degrees C for 100 h, among the best values reported in the literature. Density functional theory (DFT) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results reveal that the enhanced catalytic activity is attributed to the abundant Ce-H species, while the high selectivity results from low CO affinity. More importantly, a new reaction mechanism is proposed, which involves the reduction of bicarbonate to generate formate intermediate and CO by the H- released from Ce-H species. The new findings in this work will benefit the design of economic, efficient, and robust catalysts for low-temperature RWGS reactions.