Mass fraction of H2O. Figures 4 sho

Mass fraction of H2O. Figures 4 show the distribution of the water mass fraction inside PEMFC. So, the water is generated at the cathode, due to both water transport in the membrane and electrochemical reactions. Water transport in the membrane results from the sum of electro-osmotic transport and diffusion. While electro-osmotic drag is always moving from the anode to the cathode and the diffusion follows the concentration gradient. The formation and transport of liquid water in the cathode is an important feature that can strongly influence cell performance of a PEMFC [1, 2]. The water that is formed at the cathode must be regulated by removal or retention techniques, because the flooding of the electrodes causes a decrease in surface area in which the separation of hydrogen or the formation of water takes place. Thus, the membrane needs to be hydrated to transfer the proton, for that raison the inlet fuel must be hydrated (add water to inlet fuel), but that water naturally moves toward the cathode. This “electro-osmotic drag” is problematic at a high current densities because all the water can be removed from the anode, thus causing an abrupt loss in fuel pressure since no water will be present to transfer new protons [11, 35]. To solve this problem it is necessary to add water to the system to keep everything hydrated. The maximum value of H2O mass fraction is 0.25.