1.1.2 Introduction to SOFC

Unlike the low-temperature PEMFC, solid oxide fuel cells operate at very high temperatures ( $\sim$1000  $^\circ$C). Hydrogen is supplied at the anode, either directly or through internal reforming of another hydrocarbon fuel, and air is supplied at the cathode. The following electrochemical reactions take place in the anode and cathode triple phase boundary layers, respectively,

$${\rm H}_2 + {\rm O}^{2-} \Longleftrightarrow {\rm H}_2{\rm O} + 2e^- \;\;\;\;\;{\rm (anode \; TPB)}$$ (1.1-3)

$$\frac{1}{2}{\rm O}_2 + 2e^- \Longleftrightarrow {\rm O}^{2-} \;\;\;\;\;\;\;\;\;\;\;\;\;\;\;{\rm (cathode \; TPB)}$$ (1.1-4)

In the cathode TPB, oxygen is reduced to oxygen ions which are then conducted through the ceramic electrolyte to the anode TPB where they react with hydrogen to form water and release electrons. The electrons travel through an external circuit to a load and then back to the cathode to close the circuit.