In Situ-Formed Tridentate Pd–SO x Coordination for Sulfur-Tolerant CO Oxidation Catalysis

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SO 2 impurity, widely existing in industrial exhaust, is a typical deactivator in many catalytic reactions. The poisoning mechanism of SO 2 on the active sites of catalysts has been well acknowledged, yet the role of support in sulfur-tolerant catalysis remains elusive. Herein, TiO 2, Al 2 O 3, and CeO 2 carriers were selected to unveil the sulfur resistance mechanism of Pd-based catalysts in catalytic CO oxidation. We showed that Pd/TiO 2 effectively terminated continuous sulfidation, achieving 100% CO conversion at 175 °C for 200 h under SO 2 and H 2 O exposure. This exceptional sulfur tolerance was attributed to the formation of a distinct tridentate sulfate structure on the PdO nanoparticles, facilitated by the moderate reducibility and strong acidity of Pd/TiO 2 . In contrast, Pd/Al 2 O 3 and Pd/CeO 2 remained only ∼70 and 5% efficiency, accompanied by the abundant formation of Pd-related bidentate and Ce-related tridentate sulfate species, respectively. Combined experimental and theoretical analyses revealed the distinct in situ-formed tridentate Pd–SO x coordination over Pd/TiO 2 regulated the local electronic distribution, effectively mitigating the affinity of the catalyst to SO 2 while preserving the redox capability and reactivity of oxygen species. Our findings are crucial for advancing sulfur-tolerant catalysis, offering valuable strategies for rationally designing robust catalysts to overcome both economic and environmental challenges in industrial applications.