Chemical bulk diffusion and electrochemical properties of SmBa0.6Sr0.4Co2O5+δ cathode for intermediate solid oxide fuel cells

In this work, the chemical bulk diffusion coefficient (D-chem) of SmBa0.6Sr0.4Co2O5+delta was determined by an electrical conductivity relaxation (ECR) method. The equation of Dchem as a function of temperature in the range of 500-700 degrees C exhibits as follows: D-chem = 1.77x10(-5) (-68.039 (kJ mol(-1))/RT) (m(2)s(-1)) Electrochemical impedance spectroscopy (EIS) technique was performed over the temperature range of 600-850 degrees C to determine the cathode polarization resistance (R-p). The area specific resistances (ASR) of SmBa0.6Sr0.4Co2O5+delta-Ce0.8Sm0.2O1.9 (70:30 in wt%) composite cathode were 5.16, 0.86 and 0.210 cm(2) at the operating temperatures of 600, 700 and 800 degrees C respectively. The exchange current densities (i(o)) for oxygen reduction reaction (ORR) were determined from the EIS approach, and low-field and high-field cyclic voltammetry. The activation energies (E-a) of ORR determined from the slope of Arrhenius plots for EIS, low-field and high-field technique were 148.6, 69.8 and 74.2 kJ mol(-1), respectively. Based on the electrochemical properties, the mixed-ionic-and-electronic conductor (MIEC) of SmBa0.6Sr0.4Co2O5+delta is a potential cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs) based on a SDC electrolyte. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.