Improving the efficiency of layered perovskite cathodes by microstructural optimization

Abstract

Low-temperature solid oxide fuel cells require the use of cathodes with improved performance. In this context, microstructural optimization is fundamental in order to obtain more efficient and stable materials. However, most of the current fabrication techniques involve multiple steps and therefore they are not suitable for industrial applications. This report describes alternative strategies to prepare PrBaCo₂O_5+δ (PBC) cathodes by using a simple and economic spray-pyrolysis deposition (SP) method. Three different electrode configurations have been tested: (i) PBC prepared by spray-pyrolysis on dense CGO pellets, (ii) PBC deposited onto porous CGO backbone layers and (iii) submicrometric PBC powders prepared from freeze-dried precursors and deposited by a screen-printing process. The second approach is an alternative to the traditional wet infiltration method with a number of advantages, such as a shorter preparation time and simplicity of implementation at industrial scale. Reduced values of polarization resistance (R_p) are obtained at 600 °C, 0.027 Ω cm² for SP electrodes on porous CGO backbones, in comparison to 0.22 Ω cm² for submicrometric powder cathodes by screen-printing. Moreover, SP electrodes demonstrate improved stability with stable R_p values at 650 °C over time. A Ni–CGO anode-supported cell with an SP cathode achieves a remarkable peak power density of 0.95 W cm⁻² at 600 °C in comparison to 0.6 W cm⁻² for the cell with a screen-printed cathode.