Superhydrophobic TiO2/fluorinated polysiloxane hybrid coatings with controlled morphology for solar photocatalysis

Technological applications of polysiloxane coatings have been influenced by their intrinsic low surface energy, which increases their water repellence. Accurate control of composition and interfacial properties through the introduction of perfluorinated moieties further lowers the polysiloxane surface energy, while mixing with metal oxide nanoparticles enhances roughness, resulting in a great potential in the development of superhydrophobic materials for photocatalysis. Herein, a series of hydrophobic and superhydrophobic hybrid coatings were prepared by dehydrocoupling and hydrosilylation reactions of polymethylhydrosiloxane with 1H,1H,2H,2H‐perfluorooctyltriethoxysilane and 1,3-divinyltetramethyldisiloxane, and different polymer/TiO2 nanoparticles ratio. The chemical composition, surface morphology, and wettability studies were conducted using FTIR, solid-state NMR, EDX, SEM, contact angle measurements, respectively. Methylene blue dye decomposition under solar simulator irradiation was studied. According to the results, the polymer morphology was controlled by adding 1,3-divinyltetramethyldisiloxane into the polymeric matrix formulation, yielding a microspheres network rather than a homogenous continuous film. Accurate control over morphology allows to obtain more photocatalytic active sites as well as to form air/liquid/solid tri-phase interface resulting in approximately 7-fold enhanced dye decomposition employing 7-fold reduction of TiO2 loaded into hybrid coatings. Moreover, the composition and matrix/filler ratio plays a fundamental role in threshold control between conventional solid/liquid bi-phase or air/solid/liquid tri-phase photocatalysis.