Abstract
The kinetics of electrodes of the type oxygen, noble metal/stabilized zirconia were investigated electrochemically under equilibrium conditions. Single‐crystal cubic, polycrystalline cubic, and polycrystalline tetragonal zirconia were chosen as electrolyte materials; platinum and gold were employed as metal components. An electrode setup including a working electrode with a massive metal contact was developed and found to be suitable for well‐reproducible long‐term measurements. Impedance spectra were recorded in the temperature range from 773 to 1173 K with an oxygen partial pressure range from 1 to 101,325 Pa using a low excitation voltage. For platinum, the results indicate a uniform reaction mechanism which involves surface diffusion of dissociatively adsorbed oxygen on the metal surface as rate‐determining step. From this, the determination of characteristic thermodynamic data is possible. For gold, the results indicate a change in the reaction mechanism. The results are consistent with one mechanism, in which diffusion limitation of dissociatively adsorbed oxygen on the metal surface occurs, and a competing mechanism, in which transfer limitation of oxygen adsorbed indirect vicinity of the three‐phase boundary takes place. The comparison of the different electrolytes does not exhibit significant differences concerning the electrode kinetics.
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