Synthesis Of Ag-based Nanomaterials And Application In Electrocatalytic Reduction Of Benzyl Chloride

Organic chlorides, as a kind of important compounds, are widely used in chemicalengineering, medical and pesticide industries. However, most of them degrade slowlyand cause long-term harm to nature. Besides, they have “three-causeeffects”(carcinogenicity, mutagenicity and teratogenicity) and have a serious threat tothe environment and human health. Thus, the research on quick and efficientdechlorination becomes important and urgent from both theoretical and industrialpoints of view. Among various degradation methods, electrochemical reductionpossesses excellent efficiency of dehalogenation with the cleavage of C-X bond undera mild reaction condition. As is well known, electrode material is a very importantfactor to influence electrocatalytic process, which significantly affects the reactionspeed and reaction selectivity. Hence, the researches about electro-reduction of organicchlorides are focus on active electrode materials. So far, some studies have found thatsilver possesses extraordinary electrocatalytic property in electro-reduction of organicchlorides. However, significant barriers such as the high cost and limited resourcesrestrict its widespread application. Therefore, in order to solve these problems, thisthesis mainly focuses on developing new types of Ag-based electrocatalysts by eitherchanging the mophology and structure of Ag or doping other metal or compound. Thenthe electrocatalytic properties of the as-prepared catalysts towards the reduction ofbenzyl chloride have been studied in detail. The results obtained include the followingthree aspects:(1)1D and0D Ag-Ru mixed-nanostructures have been prepared by reducing AgNO3only in the presence of RuCl3in ethylene glycol. The characterization ofmorphology shows that the products with different weight ratios of Ag to Ru haveobvious differences. An appropriate weight ratio of Ag to Ru (Ag10Ru1) can wellcreate uniform1D nanorods in high yields (60%). The length of nanorods is about1μm and average diameter is about40nm. The structure and element compositionof the as-prepared catalysts show that they have face-centered-cubic structure andare composed of Ag and Ru with trace of RuOx(x>0).Their catalytic activitiestowards the reduction of benzyl chloride are investigated by electrochemicaltechnology. The results show that compared with Ag nanoparticles and Agnanorods, the as-prepared Ag-Ru catalysts exhibit much better catalytic activity for electro-reduction of benzyl chloride, and this improved catalytic property may beattributed to the synergistic effect between Ag and Ru.(2) Ag-Ni alloy nanoparticles with different weight ratios of Ag to Ni have beenprepared facilely by co-reduction of AgNO3and Ni(NO3)2·6H2O in an aqueoussolution with PVP as both surfactant and template and NaBH4as reductant. Theproducts are characterized by means of transmission electron microscopy (TEM),energy-dispersive X-ray spectroscopy (EDS), selected area electron diffraction(SAED), X-ray diffraction (XRD) and Ultraviolet-visible spectra (UV-vis). Theresults show that the Ag-Ni alloy nanoparticles with face-centered-cubic structureare successfully synthesized by co-reduction. The average size of particles isaround20nm. The catalytic performances of the as-prepared catalysts forelectro-reduction of benzyl chloride are investigated by cyclic voltammetry andchronoamperometric technique, respectively. The catalytic activities of Ag-Ni arecompletely different due to the difference in Ni content. Compared with Agnanoparticles, Ag-Ni catalyst with weight ratio of5:1exhibits the best catalyticactivity for electro-reduction of benzyl chloride due to the synergistic effectbetween Ag and Ni during the reduction process.(3) Ag-AgCl nanocomposites with different feed ratios have been successfullyprepared by reducing AgNO3and NaCl in ethylene glycol. Ethylene glycol is usedas both solvent and reducing agent. The element composition, morphology andstrucuture of the as-prepared nanocomposites are characterized by XRD, UV-vis,SEM and EDS. The results show that AgCl nanoparticles with an average diameterof10nm well disperse on Ag nanoparticles. The as-prepared Ag-AgCl products arehybrid with heterostructures. The electrocatalytic activities towards the reductionof benzyl chloride are investigated by cyclic voltammetry andchronoamperometric method. The results show that Ag-AgCl nanocomposites havedifferent electrocatalytic activities due to the difference in feed ratio. Ag-AgClwith feed ratio of19:1has the highest catalytic activity, and this may be relatedto the transfer and separation of electron-hole pairs.