Procedure for shutting down a fuel cell system having an anode exhaust recycle loop

A procedure for shutting down an operating fuel cell system, wherein, during operation of the fuel cell system, a continuous flow of oxidant is being provided to a fuel cell cathode from an oxidant source through a cathode flow field on one side of an electrolyte, and a continuous flow of hydrogen containing fuel is being provided to a fuel cell anode from a primary fuel source through an anode flow field on the other side of the electrolyte, and a portion of the anode flow field exhaust is recirculated through the anode flow field in a recycle loop, and an electric current is being generated by the fuel cell within an external circuit and is operating a primary electricity using device in the external circuit, the procedure including the following steps:

• (A) disconnecting the primary electricity using device from the external circuit and stopping the flow of oxidant to the cathode flow field;
• and, then, with the flow of hydrogen containing fuel continuing into the anode flow field,
• (B) connecting an auxiliary resistive load across the anode and cathode for a period of time at least long enough to reduce the cell voltage to a selected value per cell, wherein during that period of time anode exhaust continues to circulate through the recycle loop, wherein upon the cell voltage reaching the selected value, or less,
• (C) stopping the flow of fuel into the anode flow field and catalytically consuming hydrogen in the circulating anode exhaust as it circulates in the recycle loop until substantially no hydrogen remains in the loop.