Chiang Mai Journal of Science

Applications of fuel cells in industries, transportations, power plant, or various electrical devices requires scaling up from a small fuel cell to a larger one with enough power for the need of  each device.  In this study, two sizes of  the proton exchange membrane fuel cells were used. The MEA were scaled up from 5 to 50 cm² in active areas.  The platinum loading was 0.2 mg/cm² on both cathode and anode sides of each cell. The experimental results gave the maximum power output from 5 and 50 cm² fuel cells at 1.8 and 14.6 watts, respectively. It was found that the power outputs were not increased in direct proportion to the MEA size when the 5 cm² cell was scaled up to 50 cm² fuel cell. The 50 cm² fuel cell produced less voltage than 5 cm² fuel cell at the same current density, especially when it was operated in the medium and high current densities, which were in the ohmic and mass transport loss regions. However, in the activation loss region, the polarization curves of  5 and 50 cm² were not significantly different.  The cell performance of  50 cm² fuel cell decreased because larger area resulted in less homogeneity in catalyst coating, and more water production. The later led to more difficulty in water management in the cell.  In addition the less surface flatness in a larger fuel cell can reduce the surface contact leading to lower cell performance.  In addition, the effect of operating temperature in a 50 cm² cell was in the same trend as that in a smaller cell. Therefore, the temperature control for uniformity inside the larger fuel cell is a very important criterion.