Study On Tungsten Carbide Supported Palladium Anode Catalysts For Direct Formic Acid Fuel Cell

The fuel of direct formic acid fuel cell (DFAFC) which is suitable for application in the micro power supply and portable power area is non-toxic, non-flammable, safety and convenient for storage and transportation. However, the activity and stability of anode catalysts are one of the key factors that hinder DFAFCs commercial application. Tungsten carbide has a unique Pt-like structure, high stability in acid medium. But the tungsten carbide preprared by traditional methods are easy to agglomerate resulting in low specific surface area. Tungsten carbide with high specific surface area and high stability might be beneficial to improve the catalysts’performance. In this thesis, we have designed and synthesized a series of high specific surface area tungsten carbide supported palladium catalysts. We have researched on the morphologies and structures of the catalysts by modern spectroscopic microscopy and evaluated on the catalytic activities of the catalysts for formic acid electrooxidation by electrochemcal methods, the main results were as follows:(1) The highly dispersed Pd/WCx-T (x is the mean diameter of SiO2 template) catalysts were prepared by template-carbonization method. The SiO2 template, carbon source and tungsten source were mixed directly to prepare the WCx-T. The surface area of WC50-900 is 404.37 m2 g-1, which is higher than Vulcan XC-72 (250 m2 g-1). The high dispersion tungsten carbide supported palladium catalysts were prepared by impregnation reduction. Palladium nanoparticles for Pd/GW2o catalyst were uniformly dispersed on the support.20% Pd/WC10-900 showed the highest activity for formic acid electrooxidation (847.25 mA mg-1) which was 7.45 times higher than that of 20% Pd/C (113.72 mA mg"1).(2) Graphene-tungsten carbide composite (GW) was prepared by the template-carbonization method. The Pd/GWy (y is the weight percentage of WC in GW) catalysts were prepared by impregnation-reduction method. Palladium nanoparticles of Pd/GW20 catalyst with of 5-9 nm diameters uniformly dispersed on the GWy support. Pd/GW20 catalyst had a higher activity for formic acid electrooxidation (811.5 mA mg-1) than that of Pd/G (703.5 mA mg-1). The current density for Pd/GW20 catalyst only decreased 53.4% after I-t test at 0.1 V (vs. Ag/AgCl) for 1800 s, which is less than that of Pd/G (decreased 67%). The electrochemical surface area (ECSA) of Pd/GW20 only decreased 10% less than Pd/G (20%-30%), which indicated that Pd/GW20 catalyst had a good stability.