External fuel processors are not needed for MCFCs since the fuels can be reformed internally at the high operating temperatures. Internal reforming includes converting methane and steam into a hydrogen rich gas.
CH4 + H2O ⇌ CO + 3H2
At the anode, hydrogen reacts with the carbonate ions to produce water, electrons and carbon dioxide.
H2 + CO32– ⇌ H2O + CO2 + 2e–
The electrons are conducted away by an external circuit to do useful work to the cathode. Oxygen from the air and carbon dioxide from the anode react at the cathode with electrons to form water and carbonate ions.
O2 + CO2 +2e– ⇌ CO32–
The carbonate ions migrate through the electrolyte to the anode, and complete the electrical circuit. CO32– is used up at the anode; CO2 is needed at the cathode.