Experimental investigation of the biomimetic leaf-type flow field with inserting blocks for fuel cells

Optimal design of flow field and bipolar plate (BP) structure is of primary importance in increasing the power density and overall electrochemical performance of proton exchange membrane fuel cells (PEMFCs) while maintaining low pressure drop. In this study, a novel concept of biomimetic leaf flow field inserting blocks of different shapes was proposed, including semi-circular block (LCFF), three-dimensional shuttle shaped block (LSFF), and two-dimensional shuttle shaped block (LSTFF). The polarization curve, pressure drop, and impedance of PEMFCs with LCFF, LSFF and LSTFF were experimentally tested and compared with conventional parallel (PFF), serpentine (SFF) and biomimetic leaf flow field (LFF) without inserting blocks. The experimental test results presented that inserting blocks in the biomimetic LFF significantly increases the fuel cell performance compared with PFF and LFF, ant it even exhibits equivalent fuel cell performance with SFF at high air flow rate (e.g., stoichiometric ratio of 5). Moreover, compared with SFF, inserting blocks in leaf flow fields takes significant advantage in maintaining low pressure drop. In this case study, it is found that the maximum power density of PEMFC with LSTFF is about 3.92 % higher than that with SFF, while the pressure drop is only 1/10 of the latter. The electrochemical loss analysis results indicate that the leaf flow field inserting blocks decreases the ohmic loss by about 40 %–50 %, but has higher concentration loss, and the latter is significantly decreased with the increment of cathode stoichiometric ratio, i.e., air flow rate.