Temperature-driven mechanistic transition in propylene oxidation over Pt/CeO2 ensemble catalysts
Zihao Li, Xingyan Chen, Yao Lv, Sheng Dai, Huazhen Chang, Zhenguo Li, Kailong Ye, Fudong Liu, Lei Ma, Naiqiang Yan
Abstract
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.