Chapter 5. Solid Oxide Electrolysers

Abstract

Hydrogen is the most abundant element of the known Universe although its abundance in pure form on the Earth today is negligible since most of it is bound to other elements. However, hydrogen is now being seized by several technological developments as a means of energy storage. In this chapter we present the development efforts and broad panorama on solid oxide electrolysers (SOECs), in particular focusing on the operation principles and components of this environmentally friendly pathway to produce hydrogen. Solid Oxide Electrolyte Cells are advanced electrochemical devices in which H2 is produced from water and O2 is the only by-product. SOEC technology is particularly attractive in comparison to other electrolyser cell technologies due to thermodynamical advantages for electrolysis cells to operate at high temperatures (450 to 1000 °C). SOEC is seen as the technology of the future for large H2 production, since currently several feasible benign routes for energy generation are being developed coupling solid oxide electrolysers with other renewables. These hybrid technologies are capable of producing energy and store by employing hydrogen as the energy carrier. In this chapter we present the brief historical background of SOECs and their operation principles, including the electrochemical-energetic aspects and the current state of oxygen ion and proton conducting electrolysers. The most-used and novel materials are also summarized. Moreover, the trends in the area are shown and suggestions are given to overcome the known drawbacks and to improve the performance and economic feasibility, in order to enhance the commercialization of SOEC technology.