Improving water retention and mass transport for low-humidity proton exchange membrane fuel cells via a porous-channel interdigitated flow field

The power density in low-humidity proton exchange membrane fuel cells (PEMFCs) is restricted by low membrane hydration level induced ohmic loss and low efficient oxygen supply induced concentration loss. Herein, a porous-channel interdigitated flow field (PIFF) is proposed to boost the cell performance by simultaneously enhancing water retention and mass transport. A three-dimensional multi-physical PEMFC model is applied to investigate the cell performance, water transport and species distribution. It is demonstrated that PIFF is effective in improving cell performance, due to the improved dissolved water content and under-rib oxygen supply. In the same water vapor capacity, the distribution of reactants relative humidity (RH_a and RH_c) affects cell performance, where the peak power density of PEMFC at RH_a = RH_c = 0.5 is lower than that at RH_a = 0.8 and RH_c = 0.2. The peak power density can be maximumly increased by increasing rib width at the ratio of rib width increment to channel width increment (ΔW_rib/ΔW_ch) equaling to −0.5, but can be hardly increased at ΔW_rib/ΔW_ch = 2. The mode with anode gases inlet direction being totally opposite to the cathode can maximumly enhance the cell performance at low reactants relative humidity. This work provides a high-performance flow field design for low-humidity PEMFCs.