Investigation of the annealing treatment on the performance of TiO2 photoanode

Developing low-cost semiconductor photoanode toward efficient and stable oxygen evolution reaction (OER) is highly desirable for photoelectrochemical (PEC) water splitting. Herein, nanoparticulate titanium dioxide (TiO2) electrodes were prepared using Degussa P25 powders by spin-coating method. The effects of annealing conditions on the PEC performance of the nanoparticulate TiO2 photoanode was systematically investigated including temperature, annealing time and atmosphere. The results demonstrate that the TiO2/fluorine-doped tin oxide substrates (FTO/TiO2) electrode annealed at argon (Ar) atmosphere under 450 °C shows the highest PEC performance. The photocurrent density of FTO/TiO2 annealed in Ar for only 0.5 h reached to 120 μA/cm2 at 0.3 V vs. Hg/HgO which is about 10 times higher than that of the unannealed one. The X-ray photoelectron spectroscopy (XPS) results show the thermal treatment can produce oxygen vacancies on the surface of TiO2 which reduce the recombination of photogenerated electron-hole pairs and expanding the visible light absorption by introducing defective energy levels. The electrochemical impedance spectroscopy (EIS) approves that appropriate annealing treatment can effectively enhance the electron conductivity resulting in low charge transfer resistance. All these factors contribute to improving the PEC activity of TiO2 photoanode.