Dynamic evolution of Pt active sites in Pt/TiO2 during alkanes oxidation

Dynamic evolution of Pt sites in Pt/TiO 2 were studied during alkanes oxidation. • PtO x and metallic Pt sites are active for methane and propane oxidation, respectively. • Adsorbed formates intermediate remarkably affect the evolution of Pt sites. Structural evolution of active sites often significantly influences the performance of Pt catalysts, thus predicting evolution trends of active sites during reactions is crucial for governing catalytic activity. In this work, we investigated the dynamic evolution of Pt active sites in two model Pt/TiO 2 catalysts during methane and propane combustion. Pt/TiO 2 -I, prepared by wet impregnation, contains small Pt nanoparticles (∼1.5 nm) rich in oxidized Pt species (Pt 2 + and Pt 4+ ) with a fraction of 77.9%, while Pt/TiO 2 -NP, synthesized via sol-gel, has larger nanoparticles (∼6.6 nm) dominated by metallic Pt 0 (57.1%). Under steady-state conditions, Pt/TiO 2 -I shows superior activity for methane combustion (T 50 : 325 vs 415 °C), whereas both catalysts perform similarly for propane combustion (T 50 : ∼190 °C). Comprehensive characterizations demonstrate that both methane and propane combustion reactions drive significant evolution of Pt sites. Methane combustion promotes Pt particle growth, whereas propane combustion facilitates the reduction of slightly more PtO x to Pt 0 . The deconvolution of intrinsic active sites reveals that the oxidation state of Pt is more decisive than particle size during the evolution in propane and methane combustion. Specifically, the loss of exposed oxidized Pt 2+ sites primarily accounts for the deactivation of Pt/TiO 2 in methane combustion, while an increase in exposed metallic Pt 0 sites is critical for enhancing propane combustion. Moreover, the concentration of intermediate formates adsorbed on the catalyst surface should be decisive for the structural evolution of Pt active sites. These findings highlight the dynamic evolution of active sites and provide guidance for rational catalyst design. Download: Download high-res image (182KB) Download: Download full-size image