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 PtOx 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.