The oxygen electrochemical reduction at nitrogen treatedTiO2 nanotubes electrode showsdistinctive and well-separated 2-electrons reduction peaks. The oxygenreduction was investigated in alkaline solution at titanium oxide nanotube(TON) arrays fabricated by anodizing of titanium foil in hydrogen fluoridesolution followed by annealing at 450 C in nitrogen (TON-N2) atmosphere. The morphology of thearrays was characterized by SEM and the electrochemical behavior was studied bycyclic voltammetry in potassium ferrocyanide and alkaline solutions. Thetreated TON arrays showed a significant enhancement in conductivity and in theactivity for reduction of O2 in alkaline mediain comparison to the data of plain TiO2. TON arrays annealed in N2 showed a unique electrochemical behavior of two well-resolved2-electrons O2 reduction peaks incontrast to TON arrays annealed air, which only showed a single reduction peakat more negative potential. At TON-N2 arrays, hydrogen peroxide was detected as the main productduring the first reduction. The switch in mechanism is proposed to be due tothe presence of oxygen vacancies at the surface of titania nanotube arrays. Thefinding is of a high importance for the selective production of hydrogenperoxide by electrochemical reduction of oxygen in alkaline media using TiO2 nanotubes electrode.
