Size‐Dependent Hydrogen Dissociation Capacity in Ni/CeO ₂ Catalysts for Low‐Temperature CO ₂ Methanation

ABSTRACT Converting CO 2 to CH 4 under mild conditions is a promising strategy for solving environmental and energy problems, but also a challenge. In this work, the low‐temperature CO 2 hydrogenation process over Ni/CeO 2 catalysts was significantly accelerated by optimizing the H 2 dissociation ability of Ni through the size effect, thus A‐Ni/CeO 2 with an average size of 4.9 nm achieved 83.4% CO 2 conversion with ∼100% CH 4 selectivity even at 225°C. Systematic H 2 /D 2 isotopic exchange experiments, in situ spectroscopic characterizations, and density functional theory (DFT) calculations reveal that the enhanced H 2 activation ability not only promoted the creation of oxygen vacancies and hydroxyl group favorable for CO 2 adsorption/activation in the pre‐reduction process, but also the simultaneous hydrogenation of reactive intermediates belonging to carbonyl and formate pathway into CH 4 in the reaction process. This fundamental understanding of the H 2 dissociation effect on CO 2 activation and hydrogenation provides critical insights for designing catalysts with considerable low‐temperature activity, which significantly reduces energy consumption and operating costs for industrial CO 2 conversion.