Fabrication And Characterization Of CdS Nanorod And CdS-TiO₂Heterojunction

At present, the utilization of the solar energy to solve the problem of energyshortage and environmental pollution has become a hot and permanent subjectin the study of domestic and foreign researchers. It is an effective way to solvethese two problem that degrading contaminant and producing hydrogen bysemiconductor photocatalyst. Scientific research workers made great efforts todevelop high efficiency, high performance and non-pollution semiconductorphotocatalytic materials. Cadmium sulfide (CdS) is a classical Ⅱ-Ⅵcompound semiconductor materials with a direct band gap of2.42eV at roomtemperature. It shows potential applications in solar cells, optoelectronicdisplays and nonlinear optical devices because its excellent photoelectricchemical performance. The nanostructures of CdS have attracted a wide range ofresearch interests because they exhibit unique optical and electronic propertiesdifferent from the bulk state of the material. These properties closely depend onthe size and morphology so that it is essential to investigate the synthesis of CdS nanomaterials with diverse shapes and sizes. On the other hand, Compositematerials with heterogeneous interface based on CdS nanomaterials can hold upphoto corrosion, improve the photoelectric properties and photocatalyticperformance. In this article, we fabricated CdS nanorods and CdS nanorodarrays through electrochemical deposition method and solvent hot method, ThenTiO2nanoparticles was deposited on the surface of CdS nanorods. Specific asfollows:1.One dimensional CdS nanorods was synthesize by one step solvent hotmethod with cadmium nitrate,thiourea and ethylene diamine as rawmaterials.Nanorods are about50nm in diameter,about800nm in length and it iswurtzite structure.This paper researched the influence of time,temperature andmolar ratio of Cd/S for the micro morphology, crystal structure andphotoelectrochemical performance.The results indicate that:We got CdSnanorods with wurtzite structure,larger length to diameter,smooth surface whenthe Cd/S molar ratio is1:6and the sample was preservation at180℃for24h.It is easier to form the CdS nanorods instead of CdS nanoparticles with thedecrease of the Cd/S molar ratio.It need enough time and temperature to ensurethe CdS nanorods can grow up gradually and reach desired length to diameterratio.Finally,We put forward the formation mechanism of CdS nanorod:Thetemplate role of ethylenediamine played a key role in the formation of CdSnanorods.2.In order to futher improve the photoelectrochemical performance of CdS nanorods,We deposited TiO2nanoparticles on the CdS nanorods by solvent hotmethod with isopropyl titanate, isopropyl alcohol and deionize water as rawmaterial.TiO2was generated from slow hydrolysis of Isopropyl titanate.Theparticle size of TiO2is about10nm, and they are covered on the surface of CdSnanorods densely.TiO2nanoparticles can protect CdS from light corrosion andimprove the photoelectrochemical properties.The result of the degradation ofmethylene blue test show that the degradation rate of methylene blue can reath27.2％when degradation reaction continued3h with pure CdS nanorods as acatalyst,But,the degradation rate of methylene blue can reach90.3％when weuse CdS-TiO2heterojunction as a catalyst in the same condition.Thephotoelectrochemical performance of CdS nanorods is greatly ascend.3.First at all, We deposited CdS seed on a clean FTO conductive byelectro-deposition.Then CdS nanorod array was synthesised by solvent hotmethod with cadmium nitrate,thiourea and ethylene diamine as raw material.Finally, we depositied TiO2nanoparticles on the CdS nanorod array surface bythe method in2.The result show that the heterojunction with array structure ismore advantageous to hole-electronic separation,So that, thephotoelectrochemical performance of heterojunction is enhanced.The results arealso based on the photodegradation of methylene blue.In the same condition,Thedegradation rate of methylene blue can reach99.8％when we use TiO2-CdSarray heterojunction as a catalyst.Its photoelectrochemical performance isenhanced relative to the unordered CdS-TiO2heterojunction.