Durable, strong, and flexible superhydrophobic N-TiO2 silicone composite aerogels with unique air–liquid–solid triphase photocatalytic properties

TiO2 nanoparticles are promising photocatalysts for the remediation of water pollution. However, the difficulty in recycling and low light absorption of powder TiO2 hinder their application in photocatalysis. Although some studies have attempted to address these problems by immobilizing TiO2, the application of traditional immobilized TiO2 in water environment is limited because of their unstable immobilization, poor mechanical strength, low light utilization, high electron-hole recombination,and unsatisfactory photocatalytic performance. In this study, flexible superhydrophobic Nitrogen-doped TiO2 (N-TiO2) silicone composite aerogels were achieved by copolymerization of γ-methacryloxypropyl trimethoxy silane (KH570)-grafted N-TiO2 with methyltrimethoxysilane and dimethoxydimethylsilane. These flexible composite aerogels possess improved mechanical strength and stable immobilization of N-TiO2. Moreover, an air–liquid–solid triphase photocatalytic interface was formed by the superhydrophobic surface of composite aerogel, solution and the air layer existed between them. This triphase photocatalytic interface enabled oxygen at the reaction interface to be directly and rapidly supplied from the air layer, thus photogenerated electrons from the photocatalyst surface can be effectively removed and the recombination of electron holes can be reduced. Besides, the flexible photocatalyst was molded into water grass shape and placed in a water channel to verify its photodegradation efficiency and durability under hydrodynamic conditions. Experimental results confirmed that the proposed flexible photocatalyst with a triphase catalytic interface has application prospects for the degradation of pollutants in water environment.