Effect of Urea Addition on Anatase Phase Enrichment and Nitrogen Doping of TiO₂ for Photocatalytic Abatement of Methylene Blue

TiO₂-based materials are commonly employed as photocatalysts for industrial wastewater treatment. The primary reasons of employing TiO₂ include cost effectiveness, ready availability, eco-friendliness, non-toxic behavior, and exceptional resistance towards photo-corrosion. However, the wider band gap of pure TiO₂ restricts its performance because of its optical absorption of solar light to the ultraviolet (UV) region only, and to some extent of photo-excited charge recombination. In the present work an attempt is made to develop a facile synthesis approach by using urea, a cheap chemical precursor, to form nitrogen doped TiO₂ with the key objective of extended light absorption and thus enhanced photocatalytic performance. It was also observed that the urea-induced anatase phase enrichment of TiO₂ is another key factor in promoting the photocatalytic performance. The photocatalysts prepared by varying the amount of urea as a nitrogen dopant precursor, are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and photoluminescence (PL) to evaluate their crystallinity, morphology, functional groups, and charge separation properties, respectively. Moreover, the surface area was also estimated by physicochemical adsorption. The maximum nitrogen-doped sample yielded >99% photodegradation efficiency of methylene blue (MB) dye-simulated wastewater as compared to a pure TiO₂ sample which exhibited 6.46% efficiency. The results show that the simultaneous factors of nitrogen doping and anatase phase enhancement contributes significantly towards the improvement of photocatalytic performance.