N-doped TiO2/sepiolite nanocomposites with enhanced visible-light catalysis: Role of N precursors

Several nitrogen-doped TiO2/Sepiolite (N-TiO2/Sep) photocatalysts were prepared via microwave-hydrothermal treatment using four different types of nitrogen sources: ammonium hydroxide, urea, ethylenediamine and triethylamine. The obtained nanocomposites were characterized by using XRD, TEM, BET, XPS and UV-vis techniques. The results revealed that the chemical and morphological properties of the nanocomposites were significantly dependent on the nitrogen source. The interstitial N doping occurred in the form of N-O-Ti-O and the surfaces of the samples were modified by carbon species from dopants. As compared to that of the undoped sample, N-doped samples exhibited a red shift in the band gap transition. The results of simulated solar light photocatalytic activities demonstrated that NTS-EDA exhibited better photocatalytic activity than singly N-doped (i.e., no carbon) or undoped TiO2/Sep sample. The enhanced solar-light activity is attributed to the low band gap energy with N-doping, the high adsorption capacity and uniform distribution of titania nanoparticles with sepiolite as support, and the appropriate carbon content of the dopants.