Photodegradation of phenol by N-Doped TiO₂ anatase/rutile nanorods assembled microsphere under UV and visible light irradiation

N-doped TiO₂ anatase/rutile nanorods assembled microspheres were successfully synthesized via a simple and direct sol–gel method containing titanium-n-butoxide Ti(OBu)₄ as a precursor material, nitric acid as a catalyst, and isopropanol as a solvent. By manipulating calcination temperature, the photocatalyst consisting of different phase compositions of anatase and rutile was obtained. The prepared TiO₂ nanoparticles were characterized by means of x-ray diffraction (XRD), field emission scanning microscope (FESEM), atomic force microscopy (AFM), Brunauer–Emmett–Teller (BET) analysis, UV–Vis–NIR spectroscopy, and fourier transform infrared (FTIR). The results from UV–Vis–NIR spectroscopy and FTIR revealed the direct incorporation of nitrogen in TiO₂ lattice since visible absorption capability was observed at 400–600 nm. XPS study indicated the incorporation of nitrogen as dopant in TiO₂ at binding energies of 396.8, 397.5, 398.7, 399.8, and 401 eV. Calcination temperature was observed to have a great influence on the photocatalytic activity of the TiO₂ nanorods. The photocatalytic activity of the prepared mixed phase of anatase/rutile TiO₂ nanoparticles was measured by photodegradation phenol in an aqueous solution under UV and visible irradiations. N-doped TiO₂ anatase/rutile nanorods assembled microsphere (consists of 38.3% anatase and 61.7% rutile) that was prepared at 400 °C exhibited the highest photocatalytic activity after irradiated under visible and UV light for 540 min. The high performance of photocatalyst materials could be obtained by adopting a judicious combination of anatase/rutile prepared at optimum calcination conditions. - Highlights: • Synthesis of N-Doped TiO₂ Anatase/Rutile Nanorods via simple preparation method. • Direct incorporation of HNO₃ as the nitrogen dopant source. • The photocatalytic properties were studied upon UV and visible light irradiation. • The optimum calcination temperature is 400 °C for high photocatalytic activity