Preparation, Characterization And Photocatalytic Property Of Nano Cu₂S And Its Nanocomposites

Due to the double significance of "energy conservation" and "environmental protection", semiconductor photocatalytic technology has been widely studied and used in the fields of wastewater treatment, semiconductor sterilization and the purification of environmental pollutants. Most wide bandgap semiconductors have been studied among these semiconductor photocatalysts, such as ZnO, TiO2, and SnO2. However, due to their large band gap energies, the utilization rate of the sunlight is very low for them. In addition, the recombination property of photogenerated electrons and holes, hindering the pratical applicatons of the single semiconductor. So, in order to enhance the photoactivity of the single semiconductor photocatalyst, we need to take some efficient measures to modify the single photocatalyst. As a new p-type semiconductor material with a bulk band gap in range of1.22-1.24eV, Cu2S has excellent thermal and chemical stability and is a good photoelectric material. So it has great potential applications for the solar photovoltaic and environmental purification.In this thesis, Cu2S nanomaterial and its nanocomposites have been considered as the objects and synthesized by polyol process. The samples are characterized by XRD, FESEM, EDS, XPS, FTIR and UV-Vis DRS. Besides, we studied the effect of various factors on the structure, morphology and the photoactivity of the samples and the detailed contents are as the following three aspects:1. Cu2S nanomaterials with different structure and morphology have been successfully prepared by polyol process under the different reaction conditions. Copper acetate as a precursor and diethylene glycol as both solvent and reducing agent in the polyol process. Besides, we have studied the effect of the different structure and morphology on the photocatalytic activity of the samples. When the Cu/S MRs are1:1.5and1:1, the characteristic peaks of CuS appear in the XRD spectra of the samples. However, when increases the Cu/S MR up to2:1, the XRD spectra of the samples just exhibits the characteristic peaks of Cu2S. Besides, the samples show the ability to photodegrade the methylene orange. Under the2:1Cu/S, the mean particle size of the samples increases with the increasing of the reaction temperatures, which results in decreasing the photocatalytic property. 2. Taking MWCNTs as the carriers and copper acetate as a precursor, we have successfully synthesized the Cu2S/MWCNTs nanocomposites with the assistant of poly(vinyl pyrrolidone)(PVP) by polyol process, we study the influence of the different contents of copper salt and PVP on the structure, morphology and the photoactivity of the samples. When the content of the copper salt is relatively low, the Cu2S nanoparticles are uniformly dispersed on the surface of MWCNTs and the samples exhibit excellent photoactivity. However, the photoactivity of the sample decreases with increasing the content of copper salt. Under the0.02mol/L copper salt, the photoactivity of the sample increases with increasing the PVP contents. In particularly, when increases the PVP content up to0.5g, the Cu2S nanoparticles are uniformly diposited on the surface of MWCNTs and the sample shows the optimum photoactivity. However, further increasing the PVP content, the photoactivity decreases. Expecially, when increases the PVP content up to0.9g, the photoactivity decreases very much. Besides, the photocatalytic mechanism of photoactivity enhancement for the Cu2S/MWCNTs nanocomposites is also discussed.3. Similarly, taking copper acetate as the precursor and DEG as both solvent and reducing agent, we have successfully synthesized the coupled Cu2S/T-ZnOw photocatalysts with the assistant of PVP by polyol process. The effect of Cu/Zn MR and PVP content on the structure, morphology and the photoactivity of the samples are discussed. The results show that the amounts of the Cu2S nanoparticles deposited on the surface of T-ZnOw are gradually increased with increasing the Cu/Zn under the0.5g PVP. Expecially, when increases the Cu/Zn up to10%, some nanoparticles aggregated into large clusters. When the Cu/Zn≤4%, the photoactivity increases with increasing the Cu/Zn. However, further increasing the Cu/Zn, the photoactivity decreases. Under the2%Cu/Zn, when the PVP contents≤0.1g, the photoactivity increases with increasing the PVP contents. When increases the PVP content up to0.3g, the nanoparticles are uniformly loaded on the surface of T-ZnOw and the sample exhibits more excellent photoactivity. However, when the PVP contents＞0.1g, the photoactivity decreases. In particularly, when increases the PVP content up to0.5g, some nanoparticles failed to deposite onto the surface of T-ZnOw and result in decreasing the photoactivity very much. Besides, we also discuss the photocatalytic mechanism of the coupled photocatalysts in this thesis.In this thesis, we have successfully synthesized the nano-Cu2S, Cu2S/MWCNTS and Cu2S/T-ZnOw nanocomposites. The results show that the nanocomposites exhibit excellent photoactivity for the photocatalytic degradation of methyl orange, which demonstrates the samples have good potential applicatons for the purification of environmental pollutants.