Highly conductive and stable electrolytes for solid oxide electrolysis and fuel cells: fabrication, characterisation, recent progress and challenges

Abstract

Hydrogen fuel cells and hydrogen production stand at the forefront of efforts to achieve net-zero emissions. Among these technologies, solid oxide fuel cells (SOFCs) and electrolysers (SOEs) are distinguished as particularly promising for broad practical application, offering superior efficiency, robust stability, cost-effectiveness, and inherent safety. Lowering the operating temperature can significantly facilitate their commercialization by improving the stability and reducing the costs associated with electrodes and the fabrication process. Furthermore, reducing the operating temperature to 600 °C enables the utilization of heat sources from industrial processes, such as steel production or various combustion systems, effectively enhancing energy recycling efficiency. At low and intermediate temperatures, SOFCs and SOECs' performance heavily relies on electrolyte conductivity. Therefore, rationally improving electrolyte conductivity under a relatively low temperature plays an important role in facilitating the widespread application of SOFCs and SOECs on a large scale. Aimed at practical application, this work delivers an extensive review of cutting-edge modification strategies intended to enhance the conductivity of several promising electrolytes and outlines the characterisation methods utilised to assess their properties. It further investigates novel synthesis techniques aimed at reducing the sintering temperature. Moreover, this paper provides a comprehensive analysis and evaluation of electrolytes tailored for large-scale implementation in SOFCs and SOECs.