Unraveling Potassium Poisoning Mechanisms over Pt/TiO₂ Catalysts for Complete Propane Oxidation

Impurity ions derived from the catalyst synthesis or operation would profoundly affect the performance of Pt-based metal oxides. In this study, we report a severe, support-dependent poisoning effect on Pt-based catalysts, with the severity varying significantly with the support material (TiO₂, CeO₂, and Al₂O₃) and the type of catalytic reaction (propane and CO oxidation). Specifically, the poisoned Pt/TiO₂ catalyst showed negligible propane oxidation activity even at 650 °C, while simple water washing restored its activity, achieving 90% propane conversion at 324 °C. In contrast, the detrimental effect of K⁺ ions was much weaker in CO oxidation or when nonreducible Al₂O₃ was used as the support. Combined characterization and theoretical calculations reveal that the oxophilic K⁺ ions passivate the active PtO_x nanoclusters and suppress redox dynamics. More crucially, the spillover effect between metal and support was blocked, such as oxygen or hydrogen spillover. Strong CO₂ and H₂O adsorption also contributed to the serious activity loss on the K⁺-poisoned Pt/TiO₂ catalyst. This work elucidates the support- and reaction-dependent poisoning role of K⁺ ions on Pt-based catalysts, offering critical insights for designing robust and efficient catalysts for deep propane combustion.