Titanium dioxide nanostructures doped with nickel and its performance in photocatalytic reduction of 4‐nitrophenol

Abstract Background In this work, we investigated the effect of nickel on the photocatalytic properties of TiO 2 nanostructures. The photocatalysts were obtained in a two‐stage procedure. First, the sol–gel method was used for obtaining TiO 2 and Ni‐TiO 2 at 1.0 wt% of Ni, which was then followed by hydrothermal treatment under highly alkaline conditions with NaOH at 110°C. Results The obtained powders were thermally treated at 400°C. The main crystalline phase was anatase for all the samples, and a lower E g value was estimated for the Ni/TiO 2 sample (3.13 eV). The specific BET areas were obtained from N 2 isotherms at 77 K, being 141 and 153 m 2 /g for pure TiO 2 and 1.0% Ni‐TiO 2 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/TiO 2 ‐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/TiO 2 ‐HT‐400 sample showed a high efficiency, reaching 100% reduction after 15 min (simulated solar radiation) and 40 min ( λ = 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 TiO 2 nanostructures was achieved mainly through the presence of oxygen vacancies along with the decrease in electron–hole recombination. © 2023 Society of Chemical Industry (SCI).