Oxidation of carbon monoxide on platinum in composite electrodes based on solid polymer electrolytes

Adsorption and oxidation of CO on platinum black, which is contained, together with a solid polymer electrolyte (MF-4SK, Nafion), or fluoroplastic in composite electrodes modeling electrodes for fuel cells, are studied in a sulfuric acid solution and on a catalytic layer in contact with a gas phase. It is shown that, upon a previous CO adsorption at -220 mV, two well-defined peaks of CO oxidation are observed on platinum black, unlike with smooth platinum. The peak at similar to 300 mV (Ag/AgCl) vanishes completely with repeated electrode polarization. The amount of previously adsorbed CO increases, and a linear adsorbate form accumulates along with a bridge form. Being an active bonding agent, the solid polymer electrolyte causes a shift of the more anodic peak potential (790-870 mV) by about 100 mV in the positive direction and slightly decreases the rate of the CO diffusion to the platinum surface. The role of fluoroplastic is largely reduced to the water removal from the electrode surface which allows the CO oxidation currents to be increased.