Fuel Cell Cathode Composite Catalyst -- Pyrochlore Tungsten Trioxide
The study found that adding the transition metal oxide into the precious metals will help improve the electrocatalytic activity. Tungsten oxide can form the synergistic catalytic effect with the noble metal platinum, and perform quite stable in an acidic environment, the composite catalyst uses tungsten trioxide as the carrier has been extensively studied. Pyrochlore tungsten trioxide has a layered structure of multi-dimensional channel, also has a three-dimensional channel, and this structure is conducive to rapid migration and ion exchange to improve the ionic conductivity; at the same time, it enhances its adsorption property, certain amount of ions embedded in the layered structure to form intercalation compound catalytic material.
Synthesis of pyrochlore tungsten trioxide by hydrothermal synthesis method, take pyrochlore tungsten trioxide and carbon as the carrier to prepare Pt / WO3-C composite catalyst which is the proton exchange film of fuel cell catalytic material. Research showed:
1. The initial pH value of hydrothermal synthesis solution in the range of 1.0~4.0, with the pH value decreasing, the synthesized pyrochlore tungsten trioxide particle size becomes smaller;
2. Compared to Pt / C, Pt / WO3 has the poorer catalytic performance, due to tungsten trioxide performs semiconducting, it is poor in electronic conductivity which affects its electrocatalytic properties;
3. The catalytic activity of Pt/ WO3-C significantly enhanced indicates that a simple mechanical mixing can not make the catalyst loaded uniformly on the carriers, while directly loading through the liquid phase can obtain a higher dispersion of the composite catalyst, thereby enhance the catalytic performance;
4. The pyrochlore tungsten trioxide which uniformly dispersed in the toner has catalytically active sites on the surface after loading platinum, the layered pore structure of pyrochlore tungsten trioxide will be benefit to deintercalation of ions, and has the ability of accepting and donating proton in the catalytic reaction process, thereby increasing the reaction rate can be caused, and form the cooperative catalysis with platinum, thereby improving the catalytic activity, and ultimately improve the energy conversion efficiency of the fuel cell.
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