Electrochemical response of several cathode configurations prepared with Ba0.5Sr0.5Co0.8Fe0.2O3-d and Ce0.9Gd0.1O1.95 for IT-SOFC

C.SETEVICH; F. PRADO; A. CANEIRO

JOURNAL OF SOLID STATE ELECTROCHEMISTRY (PRINT)

SPRINGER

Lugar: Berlin; Año: 2016 vol. 20 p. 1633 - 1643

1432-8488

The electrochemical response of Ba0.5Sr0.5Co0.8Fe0.2O3-d (BSCF) electrodes prepared by an acetic acid based gel route has been investigated by impedance spectroscopy (IS) as a function of temperature (400 ≤ T ≤ 900 °C) and oxygen partial pressure (1×10-3 ≤ pO2 ≤ 1 atm). Several electrode configurations were studied using Ce0.9Gd0.1O1.95 (GDC) as the electrolyte. These consisted of one BSCF layer (cell A), a BSCF layer with an intermediate porous GDC layer (cell B) and graded electrodes using a composite BSCF + GDC, with variations in the surface area of GDC (cells C and D). The optimum heat treatment for the electrode assemblages was determined to be around 850-900 °C. Analysis of the impedance spectra shows that at T ≥ 600 °C a low frequency (LF) contribution, associated to the gas phase diffusion is systematically the rate limiting step. All the electrodes show an intermediate frequency (IF) arc related to mixed processes. For cells A and B, the IF response is related to the oxide ion transfer at the electrode/electrolyte surface and the charge transfer at the electrode surface, while for cells C and D the mixed process involves the charge transfer and the molecular oxygen dissociation at the electrode surface.