Factors affecting oxygen reduction activity of Nb2O5-doped TiO2 using carbon nanotubes as support in acidic solution

In order to develop stable non-platinum cathodes based on group 4 and 5 metal oxides, we investigated factors affecting the use of Nb₂O₅-doped TiO₂ for the oxygen reduction reaction (ORR). Multi-walled carbon nanotubes (MWCNTs) were used as support to maintain sufficient electrical conductivity. Nb₂O₅-doped TiO₂/MWCNTs prepared by hydrolysis was heat-treated at the desired temperature for a certain time under argon containing 4% hydrogen to investigate the relationship between ORR activity and physicochemical properties such as crystalline structure and electronic state. We confirmed that the density of the low-valence state of titanium ions, Ti³⁺, affected ORR activity. In addition, crystalline distortion of Nb₂O₅-doped anatase might be essential in order to show ORR activity.