| First, water balance experiments were implemented and proved that for a thick membrane, for example, Nafion?112, the net water transport coefficients are both negative whether the anode gas was saturated or dry. Combining with the resistance measurements, it was shown that a PEM fuel cell with thick membrane could operated with dry hydrogen when Nafion?112 membrane was used. And this operating has been used in fuel cell stacks and FCE systems successfully. The cathode humidity condition has a great influence on the cell performance and water behavior under this condition. The proportion between the mass of water sweep out and the max of the vapor in the cathode should be in the rage of 1.5~1.8 to ensure a best performance for the MEA house-made. The optimized humidity of cathode should be 0.75 for the MEA house-made.Second, combing the Schroeder's Paradox, a modified diffusion model was developed to study the liquid water transport process in a perfluorosulfonic acid proton exchange membrane. The results show that the operating temperature and the gas flow rate have a great influence on the water content distribution in a membrane. And it proved that when Nafion?112 was used, the humidity of the anode could be omitted.Third, the two-phase flow in a micro-channel was simulated to study the effects of hydrophilic/hydrophobic property on the gas distribute and the waterbehavior. The volume-of-fluid model in FLUENT package was used to keep track of the deformation of liquid-gas interface. The results show that if the contact angle of channel side-wall was larger than that of MEA, it is disadvantage for gas diffusion from the channel to the gas diffusion layer. If the contact angle of channel side-wall was less than that of MEA, it is beneficial for gas transport and maintaining the performance of the fuel cells. This conclusion give a beneficial advice to how deal with the material character of the gas flow channel, and has been used in the operation of fuel cell stacks and FCE systems.
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