The preparation of anodic TiO₂ nanotube layers has been performed using electrochemical anodization of Ti foil for 4 h at different voltages (from 0 V to 80 V). In addition, a TiO₂ thin layer has been also prepared using the sol–gel method. All the photocatalysts have been characterized by XRD, SEM, and DRS to investigate the crystalline phase composition, the surface morphology, and the optical properties, respectively. The performance of the photocatalyst has been assessed in versatile photocatalytic reactions including the reduction of N₂O gas and the oxidation of aqueous sulfamethoxazole. Due to their high specific surface area and excellent charge carriers transport, anodic TiO₂ nanotube layers have exhibited the highest N₂O conversion rate (up to 10% after 22 h) and the highest degradation extent of sulfamethoxazole (about 65% after 4 h) under UVA light. The degradation mechanism of sulfamethoxazole has been investigated by analyzing its transformation products by LC-MS and the predominant role of hydroxyl radicals has been confirmed. Finally, the efficiency of the anodic TiO₂ nanotube layer has been tested in real wastewater reaching up to 45% of sulfamethoxazole degradation after 4 h.

TiO₂ nanotube layers (TNT) are prepared by electrochemical anodization of Ti foil in an electrolyte composed of ethylene glycol, ammonium fluoride, and water. The surface of TNT is modified by iron using spin-coating of Fe(NO₃)₃/IPA (isopropyl alcohol) solution of different concentrations (10 µM−100 mM). The as-prepared materials are annealed at 450 °C for 2 h to form crystalline Fe-TNT. The phase identification and surface morphology of the materials are investigated by XRD and SEM/EDX, respectively. The novelty of this work is based on the investigation of different photochemical processes that could occur simultaneously, and it includes mainly photocatalysis and Fenton-based processes since iron is a Fenton-active element and TiO₂ is a photocatalyst. To this end, the degradation of caffeine, an organic pollutant, is performed under solar-like radiation at pH = 3 using different systems that are: (i) Fe-TNT material alone; (ii) a radical precursor alone (H₂O₂ = 1 mM); and (iii) Fe-TNT combined with H₂O₂. It is worth noting the degradation mechanism of the organic pollutants occurs via advanced oxidation processes where hydroxyl radicals have been identified as the main reactive oxygen species. One of the main goals of this work is to determine the contribution of the different involved photochemical processes (photocatalysis, photo-Fenton, and photolysis) along with the potential synergy between all these processes. To resume, this work provides new insights into the concept of photochemical versatility (using Fe-TNT), which is scarcely described in the literature.