Steam effect on Gerischer impedance response of a Ni/GDC|YSZ|LSM fuel cell / anode

摘要

The electrochemical impedance response of an electrolyte supported Solid Oxide Fuel Cell (SOFC) was studied for different compositions of feed in the anode compartment. The cell was composed of Yttria Stabilized Zirconia (YSZ), as electrolyte, and commercial Nickel/Gadolinium doped Ceria (Ni/GDC) cermet and Lanthanum Strontium Manganite (LSM), as anode and cathode electrodes, respectively. The impedance responses of the anode and cathode were deconvoluted using the analysis method of differences in the impedance spectra (ADIS). This allowed focusing on the electrochemical processes, which occur at the anode electrode and analyzing them adequately via equivalent electric circuit modelling. The main finding is that the Ni/GDC anode electrode exhibits a Gerischer impedance response, characteristic of chemical and electrochemical competing processes, which was associated with the formation of OHad- on GDC oxygen vacancies as the prevailing intermediate species for the electro-oxidation of H-2 on Ni/GDC anode. It is shown that H2O plays a dominant role for the formation of the OHad- species on the GDC surface through its reaction with O2-, thus contributing autocatalytically on the promotion of H-2 electro-oxidation on Ni/GDC anode.