Abstract
Pt/CeO(2) ensemble catalysts are promising for propylene (C(3)H(6)) oxidation in vehicle exhaust, yet identifying the intrinsic active sites and understanding how the metal-support interface evolves at varying reaction temperatures remains contentious. Herein, we demonstrate that H(2)-activated Pt/CeO(2) ensemble catalysts feature metallic Pt ensembles as intrinsic active sites, lowering the 50% conversion temperature by 120 °C after hydrogen activation. Various operando characterization techniques reveal an approximately 170 °C threshold temperature for the dynamic change of the reaction models. Meanwhile, kinetics and theoretical analysis illustrates that oxygen-facilitated dehydrogenation of sp(3) C-H bonds is the rate-determining step. At low temperatures, both C(3)H(6) and O(2) adsorb and activate on metallic Pt, without CeO(2) involvement. Once the temperature exceeds threshold, C(3)H(6) fully covers Pt sites, while O(2) activates over Pt-O-Ce interfaces and participates in dehydrogenation. This study highlights the dynamic nature of oxygen activation, leading to distinct reaction temperature regimes during C(3)H(6) oxidation.