3-ELECTRODE CURRENT VOLTAGE MEASUREMENTS ON ERBIA-STABILIZED BISMUTH OXIDE WITH SPUTTERED NOBLE-METAL ELECTRODES

The anodic and cathodic polarization behaviour of sputtered porous gold electrodes on (Bi2O3)0.75(Er2O3)0.25 (abbreviated BE25) was studied as function of temperature and oxygen partial pressure using a three-electrode cell. The anodic polarization is smaller than the cathodic polarization, allowing current densities of 2 X 1O(3) A m-2 at 0.1 V and 1041 K in oxygen for oxygen evolution. Comparison with the polarization behaviour of similar sputtered platinum electrodes on BE25 shows little effect of the electrode material on the exchange current densities. This indicates that the electrolyte surface is active in the oxygen transfer process, while the noble metal electrode serves merely as current collector. Analysis of the electrode impedance shows strong influence of surface diffusion on the electrode reaction(s). For the exchange current density an unusual P(o2) dependence is observed.