Sustainable Hot-Water-Assisted Low-Temperature Crystallization of Pure TiO2 Thin Films: A Route to Stable and Reusable Photocatalysts for Water Treatment

Abstract

Low-temperature surface modification strategies for TiO₂ thin films remain critical scalable and substrate compatible photocatalytic devices. Herein, we investigate the influence hot water assisted treatment at 95 C° for 72 h on the structure, optical, and photocatalytic performance of pure sputtered TiO₂ thin films. X-Ray Diffraction revealed the formation of anatase phase with an average crystallites size of ~ 25.6 nm attend by super-hydrophilicity (contact angle < 20°). Raman spectroscopy confirm anatase peaks at 144 cm^− 1 and 638 cm^− 1, corresponding to O–Ti–O vibrational modes, while FT-IR spectra exhibited stronger O–H vibrations, indicating enhanced hydroxylation. Photoluminescence (PL) spectra revealed emission peaks at 640, 480 and 525 nm, attributed to oxygen vacancies, indicating the presence of defect-related energy states. The treatment showed high transmittance exceeding 95.5%, and reduces the optical band gap from 3.36 eV to 3.21 eV, due to increased density of oxygen vacancies and Ti^+ 3 defects states that enhance photocatalytic activity. Under low-intensity UV-visible irradiation, photocatalytic performance revealed MB discoloration from 5% (untreated films) to 68% (treated films). The addition of H₂O₂ (10 mM) further accelerated degradation, achieving complete MB mineralization within 4 h. Recycling experiments confirmed stable activity over eight cycles with negligible Ti-ion leaching (< 3 ppb). These findings highlight the strong structure activity relationship in thermally pure sputtered TiO₂ thin films and their potential for efficient, durable, and reusable photocatalytic applications in pollutant removal.

Graphical Abstract