Preparations and photocatalytic hydrogen evolution of N-doped TiO2 from urea and titanium tetrachloride

Nitrogen (N)-doped TiO2 samples with high specific surface areas were directly prepared by heating the mixture of urea and TiO2, where the TiO2 was obtained with titanium tetrachloride as precursor. The absorption spectrum of the N-doped TiO2 shifted to wavelength up to 600 nm with increasing urea contents. X-ray photoelectron spectroscopic measurements showed that the N presented in TiO2 was in the state of both molecularly chemisorbed N2 and substituted N. While both of them contribute to the response to visible light, the latter gave the prepared samples with hydrogen evolution under visible light. The apparent photocatalytic activity of water splitting demonstrated as high amount of H2 evolution was partly due to the phase transformation from anatase to rutile for the N-doped TiO2.