A Short Review on Selection of Electrodes Materials for Symmetrical Solid Oxide Fuel Cell

Abstract

Symmetrical solid oxide fuel cells (SOFCs) operate at high temperatures and consist of a dense electrolyte which is sandwiched between two electrodes. An anode acts as a fuel electrode where fuel is oxidised, while a cathode serves as an air electrode in which oxygen is reduced. However, the use of two different materials as electrodes poses several significant issues concerning durability, reliability and fabrication costs of SOFCs. Furthermore, at least two thermal steps are required for the sintering of both electrodes, thereby increasing energy usage. In overcoming these challenges posed by conventional SOFCs, the concept of symmetrical solid oxide fuel cells (S-SOFCs) has been introduced. S-SOFCs comprise of two identical materials for the anode and cathode. The use of two similar materials decreases the interfacial regions among the electrolyte and electrodes and consequently improves the compatibility among the components. Sulphur poisoning and carbon deposition at the fuel electrode can be solved by merely reversing the flow of oxidant and fuel to oxidise all the species that degrade the performance of SOFCs. Although, the electrode material for S-SOFCs requires some unique properties, such as high electrocatalytic activity for fuel oxidation and oxygen reduction, high electrical conductivity in oxygen and hydrogen/hydrocarbon environments, promising the capability to resist sulphur poisoning and carbon deposition in hydrocarbon fuels and good structural and chemical stability under actual fuel cell conditions. As the works related to S-SOFCs are limited in this respect, this paper reviews the available reports in this field to allow a better understanding of the operational mechanism and the potential of S-SOFCs.