The Oxygen Reduction Reaction on Nb-doped Titanium Dioxide Single Crystal Electrodes

Structural effects on the oxygen reduction reaction (ORR) have been studied on the low index planes of rutile TiO2 doped with Nb (0.05–1 wt%) in 0.1 mol L−1 HClO4. The order of the ORR activity at 0.20 V (vs. RHE) is TiO2(100) < TiO2(111) < TiO2(110), and the activity increases with increasing Nb concentration. The activity of TiO2(110) is 5.6 times as high as that of TiO2(100) at Nb concentration 1 wt%. The order of the ORR activity does not correlate with the amount of oxygen vacancy defects that are known as the active sites of the ORR of TiO2 nanoparticles. The ORR activity of 1 wt%Nb-doped TiO2(100) modified with melamine is 2.1 times higher than that of the unmodified one. The activity of 1 wt%Nb-doped TiO2(110) modified with melamine is the highest in the low index planes of TiO2. Modification by tetra–n–hexylammonium cation (THA+) affects the ORR activity slightly.