Preparation And Characterization Of Tungsten Carbide Series Catalysts For Oxygen-Reduction At Gas-Diffusion Electrode

At present the main studies about proton exchange membrane fuel cell （PEMFC） cathode catalyst include two aspects: （1） Platinum-based catalysts, improve the utilization rate of platinum to reduce the consumption. （2） Non-platinum-based catalysts, looking for other low-priced electrocatalysts. Tungsten carbide （WC） is widely used in many important chemical fields, such as chemical catalysis and electrochemistry because of its platinum-like catalytic behavior and excellent stability characteristics, it is regarded as a promising material to take place of noble catalytic material of platinum. And the electrocatalytic properties to oxygen reduction reaction （ORR） of WC in acid solution still need to study.In this dissertation, tungsten carbide catalysts were prepared by spray drying sphere miniaturation gas-solid reaction, tungsten carbide/carbide were preapared by incipient wetness method, and Pt nanoparticle was modified onto the surface of WC and tungsten carbide/carbide. XRD、SEM and EDS were used to investigate the chemical compositon, morphology and surface structure of the powder prepared. Then the powder of WC、Pt/WC and Pt-WC/C were made in gas diffusion electrode, and the ORR performance of the catalysts were studied from the polarization curves and AC impedance, also the catalytic mechanism was discussed.Effects of catalyst layer compositions （content of PTFE、Na₂SO₄ and conductive material） on the performance of gas diffusion electrode was studied firstly in article, then the best technics of electrodes preparation was ascertained.Using WC prepared as catalyst support, the Pt/WC catalysts were prepared by impregnation-vapor phase deoxidation and impregnation-liquid phase deoxidation methods respectively, and the results show that: Pt/WC catalyst prepared by impregnation-liquid phase deoxidation had a better performance at oxygen diffusion electrode than Pt/WC prepared by impregnation-vapor phase deoxidation, this might due to the smaller Pt particles on Pt/WC catalyst prepared by impregnation-liquid phase deoxidation.Compared to Pt/C, Pt/WC catalyst had a better electrocatalytric property, this main appeared higher current density at the same potential and positive initial potential.Pt-WC/C powder was prepared by impregnation-liquid phase deoxidation method and the activity of three catalysts to ORR were Pt-WC/C>Pt/WC>Pt/C at the potential of negative than 50 mV while the average diameter of Pt particles were Pt/C<Pt-WC/C<Pt/WC. This indicate that tungsten carbide could enhance the catalytic performance of Pt/C, but because of the small specific surface area of WC, activity of Pt wouldn’t exhibit well if all the carbon support replaced by tungsten carbide. So the proper ratio of WC、C is very important, and key research should be the preparation of catalyst with smaller Pt particles while tungsten carbide was used.