A MATHEMATICAL-MODEL OF THE POROUS SOFC CATHODE

The relative importance of diffusion, reaction rates at the interfaces and ohmic losses is theoretically investigated for a porous perovskit e cathode. Two models for the charge transfer mechanism at the cathode -electrolyte interface have been considered. The first model assumes d irect passage of vacancies from the cathode to the electrolyte and pre dicts a sharp increase of the current density at high cathodic overpot entials. The second model assumes intermediate adsorbed oxygen atoms t o be reduced at the cathode-electrolyte interface and predicts a limit ing current behaviour in the cathodic direction. By qualitative compar ison of the results with available experimental data, possible mechani sms for the cathode behavior at high overpotentials are evaluated.