Fuel cell system, method of stopping operation of the fuel cell system, and method of starting operation of the fuel cell system

A method of stopping operation of a fuel cell system including a fuel cell having an oxygen-containing gas flow field for supplying an oxygen-containing gas to a cathode and a fuel gas flow field for supplying a fuel gas to an anode to generate electricity by electrochemical reactions of the oxygen-containing gas and the fuel gas, the method comprising:

• stopping supply of electricity from the fuel cell to the outside;
• stopping supply of the oxygen-containing gas to the oxygen-containing gas flow field and stopping supply of the fuel gas to the fuel gas flow field;
• suctioning, using a pump, a gas at least from the fuel gas flow field to reduce the pressure in the fuel gas flow field;
• and
• after the suctioning of the gas from the fuel gas flow field, supplying the oxygen-containing gas at least to the fuel gas flow field for filling the fuel gas flow field and the oxygen-containing gas flow field with the oxygen-containing gas, wherein the oxygen-containing gas supplied to the fuel gas flow field is fed from an air pump which is used to supply the oxygen containing gas to the fuel cell to generate electricity.