Part of the voltage of a fuel cell is used up as a loss in irreversible processes that convert potential useful work into heat. This voltage loss is called overpotential or polarization. Voltage loss associated with the transport of gaseous species through the porous electrode is called concentration polarization. This manuscript examines voltage loss associated with anode concentration polarization as a dissipative process and determines its spatial dependence through the thickness of the anode. Background on the origin of this loss is given using analogies of transport of electrically charged and neutral species.