Preparation And Electrocatalytic Activity Of Tungsten Carbide/Natural Zeolite Nanocomposite

Tungsten carbide bears an analogy of the catalytic capability of noble metal,e.g.Pt,and higher ability to resist catalytic poisoning,such as CO and H2S,but its catalytic activity is much lower than that of noble metal.How to improve its catalytic activity is one of the difficult points and the hot topics in recent years.In order to find an approach to solve this problem,tungsten carbide/natural zeolite nanocomposite was prepared through mechanic-milled and impregnation approach with reduction-carbonization technical.Its electrocatalyticactivity was tested by powder-microelectrode mainly.In the first chapter,the structure character and preparation of tungsten carbide,the character of natural zeolite and the application of zeolite composite were briefly introduced,and in the second chapter,the experimental process was introduced.In the third chapter,the preparation of tungsten carbide/natural zeolite nano-composite was investigated.Firstly,the raw natural zeolite was milled,and then hydrothermally treated in HC1 solution;it's found that the specific surface area was increased definitely.Secondly,Zeolite pretreated was mixed with ammonia metatungsten(tungsten hexachloride)at a certain Si:W molar ratio by a ball miller(impregnation)to form W03/zeolite precursor.At last the precursor was reduced and carbonized under a mixture atmosphere of CH4/H2 at 900 ? in a furnace for a period of time.The samples were characterized by X-ray diffraction,scan electron-microscope,X-ray energy diffusive spectrum,transmission electron-microscope,and X-ray photoelectron spectroscopic.The results of XRD,SEM,EDS,TEM,and XPS show that the sample is composed of monotungsten carbide,bitungsten carbide,quartz,mordenite,clinoptilolite.The diameter of monotungsten carbide particle is around 30 nm,and bitungsten carbide is around 20 nm.The percentage of monotungsten carbide and bitungsten carbide change along with the reacted time.It's found that tungsten carbide and natural zeolite formed core-shell nanocomposite.In the forth and fifth chapter,the electrocatalytic activity of the nanocomposite for p-nitrophenol reduction and methanol oxidation were measured by micro-powder electrode.The results imply that the electrocatalytic activity of the composite for p-nitrophenol reduction is higher than that of zeolite and tungsten carbide.And the electrocatalytic activity for methanol oxidation of the sample is higher than that of granular tungsten carbide,the precursor and natural zeolite purified.The improvement of the electrocatalytic activity of the sample can be attributed to its components and composite structure.Base on the experimental results,the mechanism of the electro-reaction was proposed.There is a synergistic effect between tungsten carbide and zeolite.Based on the above results,one conclusion can be drawn that tungsten carbide decorating on the outer surface of carbon zeolite is one of the efficacious ways to improve its electrocatalytic activity.