| Titanium dioxide has become the most widely used photocatalyst due to its advantages such as non-toxic, high photocatalytic activity, low-cost and stability etc. However, there are still some open problems in the applications of it. For instance, Ti O2 can only be excited by ultraviolet light, i.e., with wavelengths shorter than ~380 nm. Only tiny amount of solar radiation(less than 5%) can be utilized to drive chemical reactions. Therefore, it is very significant to extend its absorption wavelength range to the visible region. Preparing nano-composite materials is one of useful solutions for this problem. In this thesis, therefore, Ti O2/WO3, Ti O2/HPA, Ti O2/Au fabrics composed of composite nanofibers were fabricated by the combination of “top-down”(i.e. electrospinning) and “bottom-up”(i.e. self-assembly of block copolymer) by means of “one-step” or “two-step” methods. The structures have been characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM) and X-ray diffraction(XRD). The formation mechanism of the composite nanofibers was discussed in details based on the results of X-ray photoelectron spectroscopy(XPS), differential scanning calorimetry(DSC). Furthermore, the photocatalystic properties of resultant fabrics have been investigated by taking the degradation of Rh B or acetaldehyde as an example.In the first part, the composite nanofibers of Ti O2/WO3 were prepared by electrospinning the blend solution(chloroform is adopted as the solvent) of titanium-tetraisopropoxide(i.e. TTIP), Polystyrene-block-poly(ethylene oxide)(i.e. PS-b-PEO) and phenol tungsten and subsequent calcination at 450oC. In this fabrication strategy of “one-step”, the block copolymer plays a key role which is the driving force for the selective distribution of the inorganic components. In the prepared composite material, Ti O2 and WO3 mix physically, that is to say, there is no co-crystal of them. Relative to the neat Ti O2, the composite fabrics show enhanced photocatalytic properties in the degradation of Rh B and acetaldehyde. Especially, the sample of WO3-15(with weight fraction of 15%) exhibits the best performance.In the second part, the composite nanofibers of Ti O2/HPA were prepared by electrospinning the blend solution(chloroform is adopted as solvent) of TTIP, PS-b-PEO and H3PW12O40(i.e. HPA) [or HPA modified by Polystyrene(i.e. PS-HPA)] and subsequent calcination at 450oC. In the case of TTIP/HPA/PS-PEO, there is obvious aggregation of HPA, resulting in the poor performance in the degradation of Ph B. In the case of TTIP/PS-HPA/PS-PEO, the distribution of Ti O2 and HPA is induced by the self-assembly of PS-b-PEO due to the special interaction between PS/PS-HPA and PEO/TTIP. In the prepared composite material, Ti O2 acts as the frame to provide the space for the loading of HPA. In the degradation of Ph B, therefore, the photocatalytic properties are improved remarkably comparing to the neat Ti O2. In the last part, the composite Ti O2/Au materials were prepared by “two-step” strategy. After electrospinning the blend solution of chloroform and TTIP, the Ti O2 fabrics were obtained by calcination at 450oC. Then gold nanoparticles were loaded on the surface of Ti O2 nanofibers by reducing(induced by UV radiation) HAu Cl4 in its solution. The dependence of the size and structure of gold nanoparticles on the solution concentration and radiation time was investigated systematically. Moreover, the resultant composite fabrics show enhanced photocatalytic properties, which can be attributed to the surface plasmon effect of gold nanoparticles. |
PDF Full Text Request