Synergistic Effect of Si Doping and Heat Treatments Enhances the Photoelectrochemical Water Oxidation Performance of TiO2 Nanorod Arrays

TiO2 is a very promising photocatalytic material due to its merits including low cost, nontoxicity, high chemical stability, and photocorrosion resistance. However, it is also known that TiO2 is a wide bandgap material, and it is still challenging to achieve high photocatalytic performance driven by solar light. In this paper, silicon-doped TiO2 nanorod arrays are vertically grown on fluorine-doped tin oxide substrates and then are heat treated both in air and in vacuum. It is found that the silicon doping together with the heat treatment brings synergic effect to TiO2 nanorod films by increasing the crystallinity, producing abundant oxygen vacancies, enhancing the hydrophilicity as well as improving the electronic properties. When used as photoanodes in photoelectrochemical water splitting, under the condition of AM 1.5G simulated solar irradiation and without using any cocatalysts, these nanorod films show photocurrent density as high as 0.83 mA cm(-2) at a potential of 1.23 V versus reversible hydrogen electrode, which is much higher than that of the TiO2 nanorod films without doping or heat treating. The silicon-doped TiO2 nanorod array films described in this paper are envisioned to provide valuable platforms for supporting catalysts and cocatalysts for efficient solar-light-assisted water oxidation and other solar-light-driven photocatalytic applications.