Immobilization of Titanium Dioxide Ultrathin Films onto Porous Membranes via Atomic Layer Deposition for Photodegradation of Water‐Borne Pollutants

Solar‐driven generation of reactive oxygen species via photocatalytic membranes is a promising technology for the photodegradation of water‐borne pollutants. Here, titanium dioxide (TiO 2 ) ultrathin films (11.9–28.05 nm) were grown on polytetrafluoroethylene (PTFE) and quartz‐fiber filter (QFF) membranes via atomic layer deposition. The as‐deposited (250°C) films were i) furnace annealed (300°C–1100°C) for 1 h or ii) via rapid thermal annealing (300–500°C) for 3 min. The presence of Ti coating onto/into QFF was confirmed, four times more than on PTFE. As‐deposited TiO 2 films on QFF exhibited the crystalline phase of anatase, while no peaks were observed on PTFE. Films annealed on QFF at higher temperatures did not exhibit a mixed anatase‐rutile phase, regardless of thickness. The films on QFF also exhibited significantly higher absorption of ultraviolet light (<400 nm) compared to the films on PTFE, which had limited absorption (<360 nm). Nonstoichiometric TiO 2− x films exhibited broad absorption from ultraviolet to the near infrared. The annealed films on QFF demonstrated high photocatalytic performance of about 88%–94% removal of methyl orange and 90%–97% for tartrazine 85 (compared to films on PTFE with 36% and 18%, respectively). The TiO 2− x films demonstrated improved performance compared to pure anatase TiO 2 , paving the way for improved photocatalytic membrane performance.