A fuel cell system that employs a diode electrically coupled between bipolar plates in a fuel cell of a fuel cell stack for preventing the fuel cell between the plates from reversing its polarity. The diode is a thin-sheet p-n diode including doped semiconductor layers and has a thickness relative to the thickness of the MEA in the fuel cell so that the overall stack thickness does not increase. When the fuel cell is operating properly the diode does not conduct and all of the current through the fuel cell goes through the MEA. If the electric load on the stack increases to a level beyond the capability of the fuel cell, where the potential across the fuel cell goes significantly below zero, the diode will begin to conduct so that any current that cannot travel through the MEA with the cell voltage less than one negative forward diode voltage drop is able to go around the MEA through the diode.