Titanium Dioxide Nanostructures Doped with Nickel and Its Performance in Photocatalytic Reduction of 4‐Nitrophenol

Background: In this work, we investigated the effect of nickel on the photocatalytic properties of TiO2 nanostructures. The photocatalysts were obtained in a two-stage procedure. First, the sol-gel method was used for obtaining TiO2 and Ni-TiO2 at 1.0 wt% of Ni, which was then followed by hydrothermal treatment under highly alkaline conditions with NaOH at 110 degrees C. Results: The obtained powders were thermally treated at 400 degrees C. The main crystalline phase was anatase for all the samples, and a lower Eg value was estimated for the Ni/TiO2 sample (3.13 eV). The specific BET areas were obtained from N-2 isotherms at 77 K, being 141 and 153m(2)/g for pure TiO2 and 1.0% Ni-TiO2 samples, respectively. Scanning electron microscopy confirmed the rod shape of the particles with diameters between 10 and 20 nm and length between 100 and 400 nm. X-ray photoelectron spectroscopy analysis showed the presence of oxygen vacancies and surface hydroxyl oxygen species in all samples, but in a higher ratio for the Ni/TiO2-HT-400 sample. The photocatalytic test was performed using two different radiation sources: 254 nm and a simulated solar lamp (300 W), for the photoreduction of 4-nitrophenol to 4-aminophenol, which was followed by UV-vis spectroscopy. Conclusions: The Ni/TiO2-HT-400 sample showed a high efficiency, reaching 100% reduction after 15 min (simulated solar radiation) and 40 min (lambda = 254 nm) after the first cycle, while for the second cycle these values decreased to 63% and 78%, respectively. The increase in the photocatalytic reduction of TiO2 nanostructures was achieved mainly through the presence of oxygen vacancies along with the decrease in electron-hole recombination. (c) 2023 Society of Chemical Industry (SCI).