Unraveling the Improved ORR Activities in Pt/TiO2/C Hybrids: The Role of Pt Morphology and Reactive Surface Species

Further improvements and mechanistic understanding of the electrocatalytic enhancements towards the oxygen reduction reaction (ORR) are required to meet cost/energy demands and thus enable their practical applications in polymer electrolyte fuel cells. An investigation of the electrocatalytic enhancement mechanisms and stability of controlled electrocatalysts comprised Pt nanoparticles supported on TiO2/C materials was herein performed. The catalysts were prepared by depositing Pt, over the surface of TiO2 colloidal spheres. These materials were then supported onto Vulcan carbon to produce Pt/TiO2/C. The effect of Pt coverage at the TiO2 surface as well as the Pt/TiO2 loading on carbon over their ORR activity and stability were investigated. Results indicate that the control over Pt coverage at the surface played a pivotal role on activity optimization, in which an association between Pt content at the TiO2 surface and ORR activity was established. The ORR activity and stability were superior as compared to commercial Pt/C (E-TEK). Variations in catalytic activity could be correlated with the morphological features and with the concentration of surface reactive groups. Results described herein suggest that the understanding of the electrocatalytic enhancement mechanism together with the controlled synthesis of Pt-based nanomaterials may lead to tailored surface properties and thus ORR activities.