Synthesis And Photocatalytic Performance Of One-dimensional Semiconductor Composites

Since the discovery of carbon nanotubes(CNTs)by Iijima in 1991,one-dimensional(ID)semiconducting nanostructures,such as nanotubes,nanowires,nanorods and nanobelts,have been attracting considerable attention in view of their unique structural and electronic properties.Especially in recent years,synthesis and modification of 1D nanostructures and their applications in the field of photocatalysis have garnered tremendous attention.However,the disadvantages of the traditional one-dimensional materials,such as the only UV light response of Ti02 nanotubes and the photocorrosion of CdS nanowires,limit their applications in the field of photocatalysis.Nowadays,the exploration of suitable modification process of 1D nanostructures,enhancing their photocatalytic activities and expanding their applications in photocatalysis have been inspiring ever-increasing research interest.In this thesis,CdS nanowires-CeO2 nanoparticles(CdS NWs-CeO2 NPs)composites,N-doped Ti02 nanotubes(N-TNTs)and CdS-(N-TNTs)(CdS/N-TNTs)are prepared.By using a series of techniques,including X-ray powder diffraction(XRD),X-ray photoelectron spectroscopy(XPS),UV-vis diffuse reflectance spectra(DRS),field-emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),electrochemical analysis,photoluminescence spectra(PL)and nitrogen adsorption-desorption,the properties of the samples,such as the crystal phase,elementary composition,photoresponse,morphology,electrochemical performance and specific surface area etc.,have been characterized.Three probe reactions,including liquid-phase selective reduction of nitroaromatic compounds to amines,water splitting to hydrogen and the liquid-phase selective oxidation of alcohols to corresponding aldehydes have been utilized to evaluate the activity of the as-synthesized photocatalysts.According to the above-mentioned research,we obtain the main conclusions as follows:1.we have obtained the modified 1D nanostructures via coupling them with other semiconductors or doping nonmetallic elements into them.After modification,the 1D morphologies of the composites are nearly remained.2.Compared with bare 1D nanostructures,the modified 1D nanostructures show enhanced photoactivities for the three probe reactions,which can be mainly ascribed as following reasons respectively:1)CdS NWs-CeO2 nanoparticles composites:The good interfacial contact between the CdS NWs and the CeO2 nanoparticles improves the efficiency of the separation and transfer of photogenerated charge carriers.2)N-TNTs:The nitrogen doping into the 1D nanostructures,which would expand the absorption band edge of N-TNTs to visible light area and N-TNTs with higher interfacial charge transfer efficiency.3)CdS/N-TNTs:The coupling N-TNTs with CdS could further improve the visible light absorption of N-TNTs,and N-TNTs show more advantages during the preparation of 1D composites as compared to TNTs.3.The modified 1D composites can perform as a relatively stable visible light photocatalyst under controlled reaction conditions by the appropriate use of hole scavengers.