High-Performance SOFC Electrodes Synthesized By Novel One-Step Chemical Routes

Abstract

The next generation of hydrogen-operated solid oxide fuel cells (SOFCs) will most certainly rely on high-performance ceramic and composite electrode materials manufactured from optimized routes. La0.6Sr0.4Co0.2Fe0.8O3-Ce0.8Sm0.2O1.9 (LSCF-SDC, 50 wt.% SDC) and NiO-CGO (50 wt.% NiO) composite powders, usually employed to prepare SOFC electrodes, were synthesized by two novel one-step synthetic routes, namely microwave-assisted combustion and a modified polymeric precursor method, respectively. Powder characterization was carried out by XRD and TEM. Screen-printed electrodes with different microstructures, evaluated by scanning electron microscopy, were obtained on CGO pellets. The electrochemical performances for the hydrogen oxidation and oxygen reduction reactions were investigated by impedance spectroscopy in the temperature range of 650-750 °C using flowing humidified 10% H2 + 90% N2 gas mixtures for the anodes and pure oxygen for the cathodes. By using a three-electrode configuration cell, dc polarization measurements were also performed on selected electrodes. The results of the electrochemical characterization indicated a significant dependence of the area specific resistance (ASR) on the electrode microstructure, highlighting that the electrode resistance can be manipulated by microstructural design. The best ASR values obtained at 750 °C in pure oxygen (cathode) and hydrogen atmosphere (anode) were found to be 0.18 and 0.15 ohm.cm2, respectively. The one-step Ni-CGO electrode with improved microstructure showed an anodic overpotential of 91 mV at 750 °C for a current density of 322 mA/cm2, which is amongst the best results mentioned in the literature, demonstrating that the novel one-step synthesis routes are innovative chemical ways to prepare promising SOFC electrodes.