Strong Stabilization of Co Nanoparticles by CeO 2‐x Clusters in Inverse CeO x /Co Catalysts for Enhanced CO 2 Methanation

Abstract Inverse catalysts, where metal oxide species are dispersed over metallic nanoparticles, represent a promising class of materials for accelerating various chemical reactions. However, stabilizing metal nanoparticles with a small amount of oxide clusters remains a significant challenge, as the metallic phase tends to sinter under reaction conditions due to insufficient immobilization. In this study, flame spray pyrolysis is employed to synthesize uniformly sized inverse CeO x /Co catalysts for CO 2 methanation (Sabatier reaction). It is found that small, highly reducible CeO 2‐x clusters effectively stabilize metallic cobalt nanoparticles, thereby preventing sintering even during hydrogen reduction at 500 °C and during CO 2 hydrogenation. Detailed operando characterization demonstrates that this stabilization leads to a high density of metallic Co sites interfaced with CeO 2‐x clusters, which facilitates CO 2 activation into carbonyl (CO * ) intermediates, resulting in significantly enhanced CH 4 formation rates. Notably, an inverse CeO x /Co catalyst containing 20 mol% Ce exhibits a methanation rate an order of magnitude higher than that of a CeO 2 ‐free Co catalyst. These findings highlight the dual role of CeO 2‐x clusters in both stabilizing Co nanoparticles and enhancing catalytic performance, offering a robust strategy for improving CO 2 hydrogenation performance.