Development of BSCMF system of cathode materials and fabrication of symmetrical cell (BSCMF/GDC/BSCMF) for low temperature solid oxide fuel cell applications

Abstract

ABSTRACT In the present work, cathode materials of Ba0.5Sr0.5(Co1-xMgx)0.2Fe0.8O3 system (x = 0, 0.2, 0.4, 0.6, 0.8, 1) have been produced and the effect of magnesium (Mg) doping level on cathode performance with Gadolinium doped Cerium (GDC) electrolyte was investigated. The polarisation resistance (RP) for cathode symmetric cells was measured from 600°C to 700°C under open circuit state. At 700 °C, the polarisation resistance of BSCF is 13.96 ohm-cm2 and with the addition of Mg it has decreased to 5.17 ohm-cm2. Further increase in the Mg concentration decreased the polarisation resistance up to 0.34 ohm-cm2, which is the minimum value obtained in the composition BSCMF8. It is observed that charge transfer (CT) is more in the case of Mg-rich compositions. With the increase of magnesium concentration in the cathode, RP value was observed as decreased. This is due to the high oxygen permeation flux behaviour of magnesium, which is in the B-site of the cathode. The coefficient of thermal expansion (CTE) of BSCF is measured to be 22.1 × 10−6/K and decreased to 17.45 × 10−6/K with Mg addition in the composition to BSCMF8, due to the constant oxidation state of Mg by which it suppressed the chemical expansion caused by Co.