The solid oxide fuel cell (SOFC) promises the highest efficiency of all types of fuel cells because of the high operating temperature.
The electrolyte in the SOFC is a solid ionic conductor. Most often used are oxygen ion-conducting oxides of zirconium and yttrium or at lower temperatures also from cerium and gadolinium. The two electrodes are metals or oxides, but these are purely electronic conductors, or may have a mixed conductivity (ionic and electronic). In addition to oxygen-ion conducting electrolytes also proton-conducting solids are used as electrolyte. The basic investigations are dealing with the kinetics and mechanisms of the electrochemical reactions; oxygen reduction at the cathode and hydrogen oxidation at the anode.