Water management and performance enhancement in proton exchange membrane fuel cell through metal foam flow field with hierarchical pore structure

Compressing metal foam flow field usually causes a higher pressure drop and uncontrollable pore structure while enhancing the water discharge capability of proton exchange membrane fuel cell (PEMFC). To further enhance the water discharge capability of metal foam flow field at a low cost of pressure drop, a novel metal foam flow field exhibiting hierarchical pore structure(dcoarse/dfine=2; Vcoarse/Vfine=1; dfine=0.5 mm) is first introduced. This work numerically investigates water management characteristics and output performance of novel metal foam flow field. Subsequently, 3D printing technology is employed to precisely manufacture metal foam flow fields, which are compared with several flow fields in the cathode side experimentally. Experimental results demonstrate that at 1.5 A/cm2 during 3 h, the amount of water discharge in metal foam flow field with hierarchical pore structure is close to parallel flow field, which is 1.12 times and 1.30 times that in metal foam flow field with uniform coarse pore and uniform fine pore, respectively. Moreover, compared with the previous optimized strategy, namely metal foam flow field with 75 PPI and a compression rate of 0.75, metal foam flow field with hierarchical pore structure can not only improve the maximum net power density by 9.5 % and water discharge amount by 14.1 %, but also decrease two-thirds of the pressure drop in the cathode side. This research lays the theoretical groundwork and offers technical insight for the implementation of metal foam flow fields in PEMFCs.