Controlled Synthesis Of One-Dimensional ZnS(Co)/C Nanocomposites And Its Catalytc Properties Research Of Visible Light

ZnS is a semiconductor photocatalyst material with a large band gap, but the absorption of sunlight is mainly in the ultraviolet region, the absorption of visible light is very low, which greatly limits its practical application in the light catalysis. One-dimensional carbon material (such as CNT, CNF etc.) has a unique structure and excellent performance, such as the large specific surface area, good chemical stability and thermal stability, high electron transport capability. The semiconductor ZnS and carbon materials are combined together, which can broaden its range of light response and improve their utilization of visible light. The metal nanoparticles deposited on the surface of the semiconductor can accelerate the separation of the semiconductor photo-electron and hole, thus significantly improving the efficiency of the photocatalytic of material. But most people use precious metals as Au, Ag, Pt and Pd,which have high cost, and also can’t solve the problem of catalyst’recycling difficulty. In this thesis, in situ synthesis of one-dimensional solid-state reaction ZnS/C and magnetic ZnS/Co/C nanocomposite photocatalyst use the layered metal zinc (cobalt) hydroxide as a precursor, which using salicylate (Sal-) intercalated, after control of the reaction conditions, while its composition, properties were studied. The conclusions are as follows:(1) Under precipitation method by one step, using coordination effect of small molecules Sal-and metal anions Zn2+ in the absence of the template agent and modifier agent, one-dimensional layered zinc hydroxide nanorod with Sal-as coordinating anions is synthesized, referred to as Zn-sal LHRs (layered hydroxide nanorod). The diameter of nanorods is about 100nm with uniform morphology. Using Zn-sal LHRs as precursor, the ZnS/C nanorods is prepared after in situ vulcanization and carbonization. By controlling the thermal decomposition temperature, the degree of crystallinity and size of ZnS nanoparticles are Regulated, as well as the degree of graphitization of carbon. With SEM, FT-IR, HRTEM and other characterization methods, structure composition of the obtained ZnS/C nano-materials under 400℃ with one-dimensional is analyzed. The nanorods are porous structure and the size of ZnS nanoparticle is about 5nm, evenly distributed in the carbon substrate. ZnS nanoparticles and carbon layer are connected by strong interaction of Zn-O-C bond. Carbon surface layer has a large number of hydrophilic functional groups such as carboxyl and hydroxyl, so that the surface of the nanorods has the functionalization.(2) Using a layered Znl-xCox-sal LHRs as precursor, after cured and solid thermally in situ, to obtain the magnetic ZnS/Co/C nanocomposite photocatalyst with one-dimensional bar-shaped morphology by the reaction temperature of 700℃.Thermal processing without adding a reducing agent, the small molecule salicylate itself in the pyrolysis freed reducing gas, reducting the cobalt ions to elemental cobalt, and providing the carbon source. The nanorods have uniform particle size, the size of ZnS nanoparticle and Co respectively is 15nm and about 20nm, dispersed closely in high carbon graphite substrate with the diameter of about 100nm. The metal zinc-cobalt ions’proportion of the precursor’s laminate has the adjustable performance, so the product composition ratio can be artificially modulated, achieving the purpose of regulating the amount of metal cobalt deposition and magnetic performance of catalyst.(3) Using the photocatalytic degradation of methylene blue (MB) as the reaction experiments to investigate the visible light catalytic performance of the one-dimensional ZnS/C and magnetic ZnS/Co/C catalyst, results show that ZnS (Co)/C catalysts have excellent visible light catalytic activity. Indicating that the presence of graphitic carbon, not only can improve the dispersion of nanoparticles, maintain the stability of the material, but also effectively suppress the recombination of the light generated electron-hole pair and promote electron transport ability, achieving a visible light Sensitization of the semiconductor ZnS. Surface modification of metal elemental cobalt further improves the electron transfer rate, but the magnetic of the catalyst makes the ZnS/Co/C nanocomposite photocatalytic material can be effectively separated under an external magnetic field to achieve its multiple recycling.