Water management and structure optimization study of nickel metal foam as flow distributors in proton exchange membrane fuel cell

Abstract

In order to tackle the water flooding issue in proton exchange membrane fuel cell (PEMFC), the effects of structure parameters of nickel metal foam on water management and the performance of PEMFC were experimentally investigated. Experimental results indicated that when compression ratio of nickel metal foam on cathode is beyond 0.69, the voltage of PEMFC is completely stable in a 3-hour constant current density test. Furthermore, the performance of PEMFC enhances with the rise of compression ratio on cathode. However, there is an optimal compression ratio of nickel metal foam on anode, namely 0.38. Regarding PPI (pores per inch) of nickel metal foam, it has been found that there is an optimal PPI on cathode, namely 75, due to the synergic effect between the distribution of reactant gas and water management in nickel metal foam flow fields with different PPIs. In contrast with cathode, a higher PPI of nickel metal foam results in better performance on anode. Compared with the case that uncompressed nickel metal foam with 110 PPI for anode and cathode, the maximum power density and energy conversion efficiency of the optimized metal foam fuel cell, namely 110 PPI and compression ratio of 0.38 for anode and 75 PPI and compression ratio of 0.75 for cathode, increase by 9.8% and 4.6%, respectively. In order to further intensify the performance of PEMFC, the effect of assembly force was considered. Since nickel metal foam could protect the MEA, a higher assembly force can be tolerated to obtain better performance.