The main advantages of the fuel cells are their high energy conversion efficiency and low noise, as well as their high power and energy density even under consideration of the H2-tank The main goal of the PEMFC modeling is to calculate the cell potential and its efficiency. For this purpose it is necessary to find out which processes contribute to the potential losses and the extent of their contribution. If Ohmic voltage drops across GDLs and bipolar plates are neglected, the PEMFC potential is expressed by the equation