WC Based Composites:Preparation, Structure And Electrocatalytic Activity

In this dissertation, WC-C composites were obtained through three different methods in which tungsten precursor was AMT. The electrocatalytic property of Pt deposited WC-C catalysts and the relationship between electrocatalytic property and structure of supports were evaluated and discussed. The following three aspects have been covered.1. In this part, Vulcan XC-72R was taken as the carbon source. The influence of different reaction temperature and concentration of HNO3 on the change of carbon were observed to determine the proper condition of nitric acid treatment of decorating oxygen containing groups on carbon. The WC/C composite was synthesized through supporting AMT by NaBH4 reduction-fixation method on pretreated carbon and reduction carbonization process. The catalytic behavior of catalysts which synthesized from different carbon/AMT mass ratio for ethanol oxidation was compared.2. In the second part, the organic carbon was taken as the carbon source. The WC support with nano-size and fine dispersion was made by carburizing the mixture prepared with polymerizatio n reaction between citric acid and ethylene glycol in the existence of AMT. This method prevented WC particles from aggregation during high temperature carbonization and increased the WC content in WC-C composite at the same time. Pt or Pt-Sn particles were supported on WCa material with high surface area obtained from reaction temperature at 110℃. The effect on the catalytic performance because of the addition of Sn and different Pt-Sn reduction method was studied. PtSn-1/WCa catalyst fabricated by microwave-assisted ethylene glycol reduction method shows higher electrocatalytic properties for ethanol oxidation. The catalytic behavior increased as the increasing of temperature of electrolyte system and scan rate.3. The synthesis of C@WC compsite with core-shell structure was carried out through polymerization reaction and reduction carbonization procedure, using solution of water and alcohol as solvent, SDBS as surfactant, NH3 as catalyst for polymerization, resorcin (R) and formaldehyde (F) as monomers, AMT as tungsten precursor. Carbon nanospheres (CS) were obtained by the same procedure in the absence of AMT. The core-shell structured C@WC composite had uniform size, fine dispersion and regular shape. According to experiment results, the mechanism to synthesize C@WC was suggested. Compared with Pt/CS, the series of Pt/C@WC catalysts in which the C@WC supports were prepared from different mass ratios of R and AMT exhibited higher performance, demonstrating the enhancement for the addition of WC. The Pt/C@WC with a mass ratio of R and AMT as 1:0.084 exhibited supreme performance.