Abstract
This chapter presents an overview of the status of research into inorganic membranes and solid oxide electrolysis cells. Both can be used for gas separation, while solid oxide-based membrane fuel cell research has focused on generating electrical energy. Microporous membranes made from silica, carbon, and zeolite are initially discussed, before dense metallic and ceramic membranes are considered. Progress made toward developing fluorites and perovskite materials for membrane technologies is also discussed. This is followed by an overview of recent progress into high-temperature solid oxide cells for gas separation processes and fuel cell applications and discusses the basic operating principles of both electrolysis and fuel cells. In addition, challenges in designing high-performance electrodes, electrolytes, and issues relating to degradability and long-term durability are also examined. Crucially, the thermal energy needed to operate solid oxide cells can be supplied from external sources like industrial waste heat. In the electrolysis mode, electrical energy from renewable energy sources can be used to power these cells. In the fuel cell mode, these cells are promising electrochemical conversion devices with high electrical efficiencies and fuel flexibility. Typically, gases like hydrogen (H2) and oxygen (O2, usually from air) are supplied, and through the electrochemical oxidation of H2 (as fuel), electrical energy is generated. The review concludes with a discussion of the challenges facing these devices, and future research needed for further development. It is believed that future developments in producing new nanomaterials and improvements in material properties of existing materials, combined with advanced fabrication processes, will deliver commercially viable and large-scale manufacturing of these devices soon.