A fuel cell system includes a fuel cell having an electrode, and an electrochemical cell having a device. The electrochemical cell includes a cathode, an anode in fluid communication with the electrode of the fuel cell, and an electrolyte in electrical communication with the cathode and the anode. The device is in electrical communication with the anode of the electrochemical cell and adapted to vary the potential of the anode. The electrochemical cell and the device are capable of reducing an amount of carbon monoxide that enters the fuel cell system.