Enhanced oxygen reduction kinetics of IT-SOFC cathode with PrBaCo2O5+δ/Gd0.1Ce1.9O2- δcoherent interface

Abstract

One challenge facing the development of high-performance cathodes for solid oxide fuel cells is the slow oxygen reduction kinetics. Here, we report a dual-phase cathode material, double perovskite structure PrBaCo2O5+δ (PBC) and fluorite structure Gd0.1Ce0.9O2-δ (GDC), successfully synthesized using a one-pot method, with remarkable oxygen reduction reaction activity and low polarization resistance under IT-SOFC service conditions. The coherent interface structure is formed between PBC and GDC particles, which is beneficial to alleviate the lattice thermal expansion. The introduction of the cubic GDC phase can guide the oxygen transport among PBC particles with different orientations. When measured in a symmetrical cell configuration in the air at 600 °C, PBC-10 wt% GDC electrode shows an area-specific resistance of 0.394 Ω cm2, which is about 78% lower than that of bare PBC electrode under the same situations. The charge transfer process on the electrode surface is the rate-limiting step based on the dependence of polarization resistance at different oxygen partial pressures, where the impedance analysis technique, the distribution of relaxation times (DRT), is devoted to describing the complex electrode reaction processes. The GDC introduction significantly decreases the charge transfer resistance of the PBC-GDC composite cathode. The maximum power density of lab-scale electrolyte-supported cell with PBC-10 wt% GDC cathode reaches 1302, 938, 549 and 235 mW cm-2 at 850, 750, 650 and 550 °C, respectively. Our results demonstrate that such dual-phase composites PBC-GDC produced in one step can be considered a promising cathode material for intermediate/low-temperature solid oxide fuel cells.