Preparation Of TiO₂/C Composite Fibers Though Conjugate Electrospinning And Study On The Photocatalysis Properties

Titanium dioxide (TiO2) is the best photocatalytic material nowadays. But there are still some problems in applications, such as difficulty in separation and recycle, poor catalytic efficiency and limited application fields. In this paper, two different kinds of TiO2/C composites were designed to improve the photocatalytic properties of TiO2 so that it can be easily separated and recycled as well as have broader application fields.Isopropyl titanate, polyacrylonitrile and polyvinyl pyrrolidone were used as raw material. Electrospinning technique followed by designed heat treatment was applied to prepare TiO2 fibers, TiO2 microspheres and carbon fibers with different size. Appropriate electrospinning parameters were determined by microscope observation. For TiO2 electrospun fibers, the parameters were as follows:PVP fraction (12 wt%), electric field strength (1.0×105 V·m-1) and discharge speed (0.8 mL·h-1). For TiO2 microspheres, the parameters were as follows: PVP fraction (5 wt%), electric field strength (1.3×105 V·m-1) and discharge speed (0.6 mL·h-1). For carbon fibers, the parameters were as follows:PAN fraction (14～22 wt%), electric field strength (1.0×105～1.4×105 V·m-1) and discharge speed (0.6～0.8 mL·h-1). The crystal transformation behavior, structure and thermal properties of these materials were characterized by XRD, Raman, FTIR and TG. The results showed that Ti(OiPr)4 gradually converted into TiO2 as the temperature increased. When the calcination temperature increased from 500℃ to 900℃, the crystal structures of TiO2 transformed from anatase to rutile. For carbon fibers, the maximum graphitization degree was obtained when the calcination temperature was 900℃.Conjugate electrospinning technique was applied to prepared TiO2/C side-by-side dual fibers. The SEM and TEM images demonstrated that TiO2/C side-by-side dual fibers were successfully prepared with a diameter of 500 nm. The contact angle experimental result revealed that the fiber membrane was amphiphilic. The results of the photodegradation against rhodamine B (RhB) and nitrobenzene (NB) showed that the fiber membrane can effectively degrade oil-soluble and water-soluble contaminants. Combined with the results of XRD and Raman, the TiO2/C side-by-side fibers in mixed crystal structure of TiO2 had best degradation efficiency against RhB. For NB, the fiber membrane in anatase was most efficient.Meanwhile, we used conjugate electrospinning technology to prepare TiO2/C microsphere-loaded fibers with different electrospinning parameters. SEM images showed that the microspheres evenly distributed on the surface of carbon fiber. The contact angle experimental results revealed that the fiber membrane was hydrophilicity. For photodegradation experiment against RhB, the results showed that TiO2/C microsphere-loaded fiber membrane had good mechanical strength so that they were able to maintain the original morphology in the flowing liquid, which facilitated the separation and recovery. Combined with the results of XRD and Raman, TiO2/C microsphere-loaded fibers in mixed crystal structure, which was obtained at 700℃, was the best in degradation of RhB.