In this thesis, a PEMFC stack, which can be self-humidification of passive portable hydrogen fuel cell, will be developed. The stack is developed for portable applications, so the structure of the stack is simplified as possible as we can. As the cathode directly exposed under the atmosphere, so in a long time, the membrane easily lead to excessive evaporation of water, so that performance degradation. The traditional humidifier is more complex applications are not suitable for portable, so this thesis stack developed by the use of cotton capillarity, the water from the tanks transferred to the membrane, and then by cotton and a good touch to the membrane humidifier effect, this structure without an increase in large equipment, in line with the principles of portability. The PEMFC stack is made with carbon fiber bunches for current collectors and two 8-cell banded-type MEAs, the stack can develop a high voltage by serially connecting outside of the reaction chamber. 16-cell in series when the current density is greater than 110mA/cm2, use humidification to avoid long time operation, due to water cause a voltage drop. Humidification is not only to help transfer of hydrogen ions, and the role of a cooling stack, the cells temperature is too high will not cause transpiration rate of speed. Current density greater than 250mA/cm2, although humidity can still be effective, but insufficient humidification single cotton, one hour after, the voltage drop of about 20% longer cell performance, such as humidity will be no more have a more significant decline phenomenon, more cotton or additional external humidification humidifier can maintain a long-time stable operation. Therefore, the performance of the cells in order to avoid a recession, should pay attention to in a long time when working conditions and operating range.

The improvement of performance and the maintenance of stability of a portable air-breathing PEMFC are studied in this thesis. The water content within proton exchange membrane affects strongly on the performance and stability of a PEMFC stack, in which water within membrane can form a conduction channel to provide hydrogen ion transferring from anode to cathode. The over-dried condition caused by a long time operation can also be avoided to prevent the membrane from damaging. Thus the proper humidification of a stack is important for a portable air-breathing PEMFC system. The traditional humidifier is too bulky to be suitable for portable fuel cells. A simple humidification system developed in this research is making use of the water stored in the stack bottom and the self-generating heat by chemical reaction to drive the passive humidification system of this stack. The water at the bottom of the tank can be sucked with cotton threads in cathode and a piece of cotton cloth by capillary phenomenon and transfer to the membrane of MEA. The cotton threads humidification in cathode is enough in low and middle current density in this study. It is not enough in high current density due to the large water vapor dissipation in the cathode surface, so a cotton cloth in anode is added to increase the evaporating surface to supply water to membrane. This passive humidification system does not need extra energy, and it only employs the heat generated by the cells. The system follows the simple principle, which is always obeyed in a portable fuel cell system. A 16-cell HFC stack developed in this research adopts carbon fibers as current collectors. Two pieces of 8-cell anodes is placed in the inner sides of the stack, and the 8-cell cathode is located on external sides, which is exposed directly to the ambient air. The 16-cell can connect in series or parallel. The experimental results show that it is helpful to add cotton threads in cathode and cotton cloth in anode to improve the stability of the 16-cell stack during a the long period operation. The 16-cell HFC stack has succeeded in the operation and charging for an IPhone, digital photo frame, and LED light. The experiments have proved that this type of the lightweight humidification system is helpful in the future portable hydrogen fuel cell applications.