Understanding the suppressive role of catalytically active Pt-TiO2 interfacial sites of supported metal catalysts towards complete oxidation of toluene

Because an interface plays an important role in catalytic reactions, its effects on catalysis have been intensively investigated. However, for complex reactions and substrates, the multiple steps generate different intermediates which may introduce adverse effects. Herein, to investigate the role of interfacial sites in toluene oxidation, the Pt-TiO2 interfacial perimeters are manipulated by tuning the diameter of platinum nanoparticles (2.7 nm to 12.4 nm) supported on TiO2 with similar electronic metal-support interaction, which was confirmed by XPS and CO-DRIFT. Steady-state tests show that the Pt-TiO2 interfacial sites have a suppressive effect on the catalytic performance. Detailed in situ characterizations and DFT calculation demonstrate that the Pt-TiO2 interfacial structures are preferred for the adsorption of toluene and can critically change the reaction pathway. Due to the promotional role of adjacent oxygen species, the toluene adsorbed at the Pt-TiO2 interface undergoes an early oxidative dehydrogenation process, which is more competitive than toluene desorption and degradation. The carbon-enriched species with strong adsorption are formed consequently, which occupy the active sites and block the migration of active O species for further oxidation. This work deepens a fundamental understanding of the contradictory role of interfacial sites, and provides new insights for the rational design of efficient catalysts for the complete oxidation of toluene.