Nickel-Doped TiO2 Nanoplate Synthesized via Mechanical Ball Milling-Assisted Sol–Gel Method for Photocatalytic Degradation of MB and NO

Nickel-doped titanium dioxide (NIT) with different nickel contents (0.1–1.0 wt%) was prepared via the sol–gel method, combined with mechanical ball milling. X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–Vis diffuse reflectance spectroscopy (DRS) were employed to characterize the crystalline structure, morphological characteristics, and optical properties of the samples. The photocatalytic activity was evaluated through the photocatalytic degradation of methylene blue (MB) under visible light and nitric oxide (NO) under simulated sunlight. The XRD results show that all the catalysts retain the anatase phase, confirming that nickel doping does not alter the crystalline structure of TiO2. NIT catalysts exhibited a plate-like morphology due to the ball milling treatment of the precursors. The DRS analysis revealed that nickel modification induced a redshift in the absorption edge of TiO2 and enhanced the visible-light absorption. The photocatalytic tests demonstrated that 0.5 wt% NIT and 0.7 wt% NIT exhibited the highest photocatalytic activity for MB degradation, achieving degradation rates of 93.1% and 91.4% after 60 min, respectively. Moreover, 0.7 wt% NIT showed the optimal NO conversion efficiency of 45.4% after 30 min. The improved photocatalytic performance of the sample is attributed to enhanced visible-light absorption, reduced charge recombination, and a high specific surface area. This study provides a facile strategy for synthesizing Ni-doped TiO2 nanoplates based on the sol–gel method, which is scalable in regard to the industrial production of efficient photocatalysts.