Layered perovskites as promising cathodes for intermediate temperature solid oxidefuel cells

Abstract

The suitability of GdBaCo₂O_5+δ as a cathode material for intermediate temperature solid oxide fuel cells has been evaluated. The ¹⁸O/¹⁶O isotope exchange depth profile (IEDP) method has been used to obtain the oxygen surface exchange and oxygen tracer diffusion coefficients yielding optimum values for applicability in fuel cells (k* = 2.8 × 10⁻⁷ cm s⁻¹ and D* = 4.8 × 10⁻¹⁰ cm² s⁻¹ at 575 °C) especially in terms of low activation energies (E_A^k = 0.81(4) and E_A^D = 0.60(4) eV). The same material has been characterized electrically as a part of a symmetrical electrochemical system (GdBaCo₂O_5+δ/Ce_0.9Gd_0.1O_2−x/GdBaCo₂O_5+δ), by means of impedance spectroscopy measurements, corroborating an excellent performance in the classical intermediate temperature range for solid oxide fuel cells (500–700 °C). An area specific resistance (electrode–electrolyte interface) of 0.25 Ω cm² at 625 °C was achieved for a cell processing temperature of 975 °C. Finally, layered perovskites are presented as a promising new family of materials for cathode use in solid oxide fuel cells at low temperatures.