A novel P/Ag/Ag₂O/Ag₃PO₄/TiO₂ composite film for water purification and antibacterial application under solar light irradiation

TiO₂-based thin films have been intensively studied in recent years to develop efficient photocatalyst films to degrade refractory organics and inactivate bacteria for wastewater treatment. In the present work, P/Ag/Ag₂O/Ag₃PO₄/TiO₂ composite films on the inner-surface of glass tube were successfully prepared via sol-gel approach. P/Ag/Ag₂O/Ag₃PO₄/TiO₂ composite films with 3 coating layers, synthesized at 400 °C for 2 h, showed the optimal photocatalytic performance for rhodamine B (Rh B) degradation. The results indicated that degradation ratio of Rh B by P/Ag/Ag₂O/Ag₃PO₄/TiO₂ composite film reached 99.9% after 60 min under simulated solar light, while just 67.9% of Rh B was degraded by pure TiO₂ film. Moreover, repeatability experiments indicated that even after five recycling runs, the photodegradation ratio of Rh B over composite film maintained at 99.9%, demonstrating its high stability. Photocatalytic inactivation of E. coli with initial concentration of 10⁷ CFU/mL also showed around 100% of sterilization ratio under simulated solar light irradiation in 5 min by the composite film. The radical trapping experiments implied that the major active species of P/Ag/Ag₂O/Ag₃PO₄/TiO₂ composite films were photo-generated holes and O₂·⁻ radicals. The proposed photocatalytic mechanism shows that the transfer of photo-induced electrons and holes may reduce the recombination efficiency of electron-hole pairs and potential photodecomposition of composite film, resulting in enhanced photocatalytic ability of P/Ag/Ag₂O/Ag₃PO₄/TiO₂ composite films. - Highlights: • P/Ag/Ag₂O/Ag₃PO₄/TiO₂ film showed great photocatalytic ability and stability. • 10⁷ CFU/mL of E. coli could be completely inactivated by this film within 5 min. • Photo-generated holes and O₂·⁻ radicals were the major reactive species. • This photocatalyst film could be a promising candidate for bacterial disinfection.