Increasing Pt oxygen reduction reaction activity and durability with a carbon-doped TiO2 nanocoating catalyst support

We report a conductive TiO2 nanocoating on carbon nanotubes (CNTs) as a Pt electrocatalyst support that shows a significant enhancement in Pt catalyst activity and durability for the oxygen reduction reaction. By using CNTs as the substrate for TiO2 nanocoating, the nanoscale morphology of the oxide was retained during heat treatment. After carbon doping of the TiO2 nanocoating, X-ray photoelectron spectroscopy suggests a shift in the binding energy of Ti 2p, implying a suboxide formation. The X-ray absorption near-edge structure showed the mid-edge and post-edge up to 5010 eV, which are attributed to a 1s/4p transition and promotion of a photoelectron to higher vacant orbitals of Ti and Ti-O anti-bonding states. The observed smaller coordination number implies that a suboxide was formed with substitutional carbon. On the other hand, the extended X-ray absorption fine structure showed that carbon also exists in interstitial positions. Electrochemical studies showed that the carbon-doped TiO2/CNT support has a much greater electrical conductivity than that of undoped TiO2/CNT, demonstrating that carbon doping is an effective way to achieve electrical conductivity in the oxide. Pt supported on the carbon-doped TiO2/CNTs (Pt/c-TiO2/CNTs) showed a better oxygen reduction activity than a commercial Pt/C catalyst. The catalyst only has a less than 3% loss in activity after electrochemical cycling 5000 times, as compared to an activity loss of about 55% for the Pt/C catalyst. The much better activity and durability of the TiO2 nanocoating supported Pt was attributed to the oxygen deficient oxide support surfaces and strong metal-support interactions.