An Investigation of Interfacial and Photoelectrochemical Performance of Thermally Prepared C,N-codoped TiO2 Photoanodes for Water Splitting

In the present study, C, N-codoped TiO2 (C, N-TiO2) thin film photoanodes are prepared by a thermal treatment of titanium substrates embedded in various materials such as aluminosilicates (zeolite) or alumina particles and heat treated at 500 degrees C for 3 h in a carbon contaminated muffle furnace. The prepared C, N-codoped TiO2 photoanodes showed a significant water oxidation with the highest photo currents of about 100 mu A cm(-2) at zero bias versus (Ag/AgCl) using alumina as reactant medium under a standard 1 SUN illumination of solar simulator when compared to pure TiO2 (similar to 25 mu A cm(-2)) in 1 M KOH electrolyte. The C, N-codoped TiO2 photoanode showed stable photocurrent for about 10 hours in the long term stability test. The physico-chemical properties of the prepared C, N-codoped TiO2 thin film sample was examined by Scanning electron microscopy, Energy dispersive X-rays, X-ray diffractions, X-ray photoelectron spectroscopy, UV-visible diffuse reflectance spectroscopy and electrochemical impedance measurements for light harvesting (photo absorption) characteristics. It is found that the C, N-codoped TiO2 exhibited strong absorption to visible-light region and improved electron donor density than pure TiO2 from UV-Vis absorbance spectra and Mott-Schottky analysis, respectively. The enhanced photoelectrochemical performance of the C, N-codoped TiO2 could be ascribed to the strong visible light absorption through band gap reduction and suppression of electrons-holes recombination process.