Binder-free TiO(2) hydrophilic film covalently coated by microwave treatment

A binder-free attachment method for TiO(2) on a substrate has been sought to retain high active photocatalysis. Here, we report a binder-free covalent coating of phase-selectively disordered TiO(2) on a hydroxylated silicon oxide (SiO(2)) substrate through rapid microwave treatment. We found that Ti–O–Si and Ti–O–Ti bonds were formed through a condensation reaction between the hydroxyl groups of the disordered TiO(2) and Si substrate, and the disordered TiO(2) nanoparticles themselves, respectively. This covalent coating approach can steadily hold the active photocatalytic materials on the substrates and provide long-term stability. The binder-free disordered TiO(2) coating film can have a thickness (above 38 μm) with high surface integrity with a strong adhesion force (15.2 N) against the SiO(2) substrate, which leads to the production of a rigid and stable TiO(2) film. This microwave treated TiO(2) coating film showed significant volatile organic compounds degradation abilities under visible light irradiation. The microwave coated selectively reduced TiO(2) realized around 75% acetaldehyde degradation within 12 h and almost 90% toluene degradation after 9 h, also retains stable photodegradation performance during the cycling test. Thus, the microwave coating approach allowed the preparation of the binder-free TiO(2) film as a scalable and cost-effective method to manufacture the TiO(2) film that shows an excellent coating quality and strengthens the application as a photocatalyst under severe conditions.