A Solid Oxide Fuel Cell consists of 4 layers (cells), 3 of which are ceramics. The typical layer (cell) is usually only a few millimeters thick. Hundreds of these cells are then connected in series to form a Solid Oxide Fuel Cell (SOFC) stack.
The ceramics used in SOFCs do not become electrically and ionically active until they reach extremely high temperatures. Because of this the stacks have to run at temperatures typically ranging from 500 - 1,000°C. Reduction of oxygen into oxygen ions occurs at the cathode. These ions then diffuse through the electrolyte to the anode where they electrochemically oxidize the fuel. In this reaction, a water byproduct is given off as well as two electrons. These electrons then flow through an external circuit where they can do work. The cycle will then repeat when the electrons enter the cathode material again.