OXYGEN DIFFUSION THROUGH SILVER CATHODES FOR SOLID OXIDE FUEL-CELLS

The oxygen reduction mechanism at the interface O2,Ag/YSZ (yttria-stab ilized zirconia) was investigated by impedance spectroscopy and curren t-overpotential recording. Oxygen partial pressure was varied between 10(-4) and 1 atm, and temperature between 600 and 850-degrees-C. Both dense and porous silver electrodes were studied. Bulk diffusion of oxy gen atoms through the solid silver was identified as the rate-determin ing mechanism. A second, smaller contribution is ascribed to dissociat ive adsorption of oxygen molecules on the silver electrode. Good agree ment with known data for the diffusion and solubility of oxygen in sil ver is obtained.