Composite hollow nanostructures composed of carbon-coated Ti3+ self-doped TiO2-reduced graphene oxide as an efficient electrocatalyst for oxygen reduction
Cost-effective durable and highly active electrode materials have become greatly desirable in the electrocatalytic oxygen reduction reaction (ORR), a crucial element in energy devices. In particular, the low intrinsic conductivity and poor reactivity of TiO2 are believed to hinder the efficient applicability of this material as an ORR catalyst. Herein, we report for the first time an efficient one-step approach to synthesize conductive Ti3+ self-doped carbon-coated TiO2 anchored on reduced graphene oxide (rGO) hollow nanospheres. A remarkable 11-fold improvement of the conductivity of TiO2 with an optimized rGO(10%)/TiO2 sample is herein reported. The rGO/TiO2 hollow nanospheres unveiled comparable activity to a conventional Pt/C reference. Most importantly, improved stability and remarkable methanol tolerance were achieved. The results were attributed to a cooperative effect of the hybridization of TiO2 with rGO, Ti3+ self-doping and the formation of a carbon-coating layer over the TiO2 particles. The selected design for the morphology of this novel electrocatalyst was further confirmed to play a crucial role in providing an enhanced number of active sites for oxygen reduction. This new nanocomposite is believed to exhibit promising applicability in a wide range of research areas including energy storage and conversion, photocatalysis, and gas sensors.