Surface degradation of strontium-based perovskite electrodes of solid oxide fuel cells

Abstract

Solid oxide fuel cells (SOFCs) are chemical-to-electrical energy conversion devices that consist of ceramic and metallic materials. The electrodes of SOFCs function as sites for electrochemical reactions, and as electronic conductors to transfer charge. The strontium-based perovskite electrode has been considered because it offers ionic and electronic conductivity, and tolerance to reduction-oxidation cycling. However, as shown in this work, exposure to humidity greater than 40% relative humidity, that may be present during non-operation conditions, including storage, can result in changes in the electrode surface composition with resulting degradation of electrical performance. This study investigates the physical-chemical and electrical characteristics of electrode surfaces when subjected to various humidity and temperature conditions, using scanning electron microscopy, energy dispersive spectroscopy, X-ray fluorescence spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction techniques. Electrode phase decomposition, along with strontium-based degradation mechanisms, were found at humidity levels greater than 40% relative humidity.