Effectively regulating Ni distribution on CeO2 through formation of Ce1−xNixO2−y solid solution to enhance the selectivity in RWGS reaction
Nickel-based catalysts frequently encounter significant challenges in achieving both high CO 2 conversion and superior CO selectivity during reverse water gas shift (RWGS) reactions. To address this issue, we developed a facile strategy to prepare highly dispersed Ni/CeO 2 catalysts by forming Ce 1−x Ni x O 2−y solid solutions. Under conditions of 300–600 °C, 0.1 MPa, and a gas hourly space velocity (GHSV) of 40,000 mL g cat −1 h −1 , the 5Ni/CeO 2 -A catalyst exhibited outstanding selectivity, approaching 100 %. The RWGS reaction rate reached 1332 μmol CO g Ni −1 s −1 and maintained stable for 50 h almost without deactivation. The formation of Ce 1−x Ni x O 2−y solid solution uniformly disperses numerous Ni species in the CeO 2 lattice, effectively inhibiting Ni aggregation. This highly dispersed Ni weakens CO adsorption and facilitates its direct desorption without excessive hydrogenation. Moreover, the catalyst remains well-dispersed state even after reduction. The formed Ce 1−x Ni x O 2−y solid solution generates abundant oxygen vacancies on the catalyst surface, enhancing H 2 dissociation. The catalyst’s pore size distribution is also modified, creating stacked pores that favor reactant diffusion and expose more active centers. In-situ DRIFTS experiments demonstrate that Ce-OH plays a pivotal role in CO 2 adsorption on the 5Ni/CeO 2 -A catalyst, while the stabilization of bicarbonate and formate intermediates by the highly dispersed Ni further promotes catalytic performance. This study introduces a novel preparation method and provides valuable insights for designing Ni-based catalysts with exceptional CO selectivity.
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