Method for shutting down a system containing a fuel cell stack and system comprising a fuel cell stack

1. A method for stopping a polymer electrolyte membrane fuel-cell stack, the fuel-cell stack comprising a stack of cells and being installed in a system comprising a fuel-gas supply circuit connecting a fuel-gas tank to the anode of the fuel-cell stack, and an oxidant-gas supply circuit connected to an oxidant-gas tank, or to atmospheric air, the method comprising a procedure for shutting down the fuel-cell stack comprising the following steps:

(i) cutting off the supply of fuel gas and oxidant gas;

(ii) continuing to draw current until the oxidant gas is sufficiently consumed; and

(iii) injecting gas enriched with nitrogen into the oxidant-gas supply system,

wherein the method further comprises the step of completely eliminating the hydrogen still present at the anode of the stack, and

wherein the step of eliminating the hydrogen comprises an electrochemical pumping step, implementing an electrochemical membrane installed outside of the stack.

2. A method for starting up a polymer electrolyte membrane fuel-cell stack having undergone a stopping procedure according to claim 1 , the starting-up method including an initial step of suction of oxidant gas present at the anode before injecting the fuel gas.

3. A system containing a fuel-cell stack, said system comprising a gas circuit and a stack of electrochemical cells forming a fuel-cell stack comprising a polymer ion exchange membrane, said circuit comprising:

a fuel-gas supply circuit connecting a fuel-gas tank to the anode of the fuel-cell stack; and

an oxidant-gas supply circuit connecting an oxidant-gas tank, or atmospheric air, to the cathode of the fuel-cell stack;

wherein the system furthermore comprises means able to completely eliminate the hydrogen present at the anode of the fuel-cell stack, and

wherein the means able to completely eliminate the hydrogen comprise a resistance installed in parallel with the fuel-cell stack.

4. The system according to claim 3 , wherein the means able to completely eliminate the hydrogen comprise a polymer membrane installed outside of the stack.