The PEMFC (polymer electrolyte membrane fuel cell) is a kinds of electro – chemical system to exchange chemical potential energy of gases, especially hydrogen and oxygen, to electrical energy. The system always makes water as a reactant of gases or condensation of slow humidity of gases. Hydrogen gas is diffused from channel to gas diffusion layer. And when it touches the anode catalyst layer, then hydrogen is ionized and generate electron. Membrane has high proton conductivity but low electrical conductivity. So the electron does not move toward membrane and it moves toward GDL and outer circuit. On the other hand, hydrogen ion passes through the membrane and at the cathode side catalyst layer, hydrogen ion, oxygen, and electron meet and generate water and electricity.