The open cell voltage (Voc), when no current is drawn (no external voltage is
applied), is the maximum attainable voltage for a given fuel cell. At low current
densities, the non-instantaneous reaction kinetics result in a rapid voltage drop
from Voc. At intermediate current densities, there is a linear drop in voltage. This
is due to Ohm’s law, V = IR, as there is some resistance to electrical flow in the
fuel cell components. At the higher current densities, the hydrogen consumption
rate begins to approach the mass transfer rate (hydrogen must be transported
through the diffusion layer to the catalyst). Fuel cells are typically operated in the
ohmic loss region. When judging fuel cell performance, the amount of electrical
power produced is of the greatest interest. Electrical power is calculated from