Developing Robust\nCeria-Supported Catalysts for Catalytic\nNO Reduction and CO/Hydrocarbon Oxidation

Synthesis of robust and hydrothermally stable PGM/ceria\nmaterials\nfor NO, CO, and hydrocarbon abatement remains a formidable challenge,\nas ceria and PGMs are known to sinter severely >800 °C under\nhydrothermal conditions, leading to irreversible activity loss. Herein,\nwe tackle this challenge by synthesizing well-defined catalysts with\natomically dispersed rhodium supported on ceria with varying abundance\nof (100), (101), and (111) facets. Evaluation of these catalysts for\nNO reduction by CO as well as CO and propylene oxidation under model\nand industrially relevant conditions reveals pronounced reactivity\nand stability differences. Different modes of interaction of Rh ions\nwith the ceria facets and their facile reducibility were shown to\nbe the crucial parameters controlling reactivity, resulting in pronounced\nactivity and stability variations. Facet-dependent poisoning of surfaces\nby nitrites was identified as the main reason for deactivation of\nthe catalysts at low temperature, which is mitigated for (111) ceria\nfacets. (111)-enriched ceria nanoparticles survive very harsh hydrothermal\naging at 950 °C by maintaining and preserving (111) facets, unlike\nother ceria nanoparticles which sinter into poorly defined shapes.\nThus, putting atomically dispersed PGM sites on (111) ceria facets\nlead to the catalytic material with the highest activity and stability\nfor all studied reactions, providing the pathway to catalysts that\ncan endure extremely harsh hydrothermal aging conditions.