Metal / Polymer Composite Catalytic Materials Used In Fuel Cells

This paper mainly studied the new composite catalystic materials cobalt-polypyrrole-carbon (Co-PPy/C) and co-polythiophene-carbon (Co-PTh/C) applied to oxygen reduction reaction (ORR) in fuel cell. Their synthesis conditions such as the carbon materials, treatment of carbon, polymerization temperature and oxidant were studied as well as their electrocatalytic performances for ORR.The synthesis conditions of Co-PPy/C were deeply investigated. Compared with untreated carbon, carbon black pretreated in acid used as carrier for Co-PPy/C composite catalyst improved ORR catalytic activity significantly, with the current density increased 30mA·cm-2. Comparison of different polymerization temperatures and oxidant catalysts showed that with zero temperature and hydrogen peroxide as the oxidant catalyst could obtain the composite catalyst with the highest catalytic activity. The electrode with Co-PPy/C as catalysts in 6mol·L-1 KOH in air atmosphere showed good catalytic performance, with the current density of 96 mA·cm-2 at-0.20V(vs.Hg/HgO).The composite catalysts Co-PTh/C were first designed and synthesized. The particles were spherical with the size of 10 to 30 nm and dispersed uniformly. Compared with the mass fraction of 5% Pt/C, the catalytic activity of Co-PTh/C towards ORR in 6mol·L-1 KOH showed a better activity, with a current density of 158mA·cm-2 at-0.20V (vs.Hg/HgO).The catalytic mechanism of ORR on Co-PPy/C and Co-PTh/C were preliminarily studied. The conclusion was that there existed Co-C-N and Co-C-S sites in the Co-PPy/C and Co-PTh/C composites which were reponsible for their high catalytic activity towards ORR.The cells were assembled respectively by gas diffusion electrode as positive electrode, pure zinc as negative one and 6mol·L-1 KOH as the electrolyte. The cells with catalysts Co-PPy/C and Co-PTh/C discharged voltage of 0.95V and 1.05V respectively under the condition the of 60 mA·cm-2 for constant current discharge. The cells showed good performance with platform stability.