Fuel cell and method for stopping a fuel cell

The fuel cell stack (1) may be supplied with oxygen or with atmospheric air as oxidant gas. The fuel cell stack includes a device for filling with pressurized atmospheric air comprising an air intake orifice (126), an oxidant gas recycling loop (12R) and apparatus for isolation from the atmospheric air, such as an isolation valve (128), a cut-off valve (120) or a non-return valve, enabling the supply channel to the cathodes and said recycling loop to be isolated from the atmospheric air. This makes it possible to implement a shut-down procedure comprising the following actions: (i) the supply of fuel gas and oxidant gas is cut off; (ii) current continues to be drawn so as to consume the oxidant gas remaining in the oxidant gas supply system; and (iii) nitrogen-enriched gas is injected into the oxidant gas supply system. Upon being shut down, the fuel cell stack is under conditions preventing degradation thereof by shutting down the internal electrochemical processes so as to guarantee that a hydrogen/nitrogen mixture remains in the fuel cell stack after it has been extinguished.