Novel complementary cathode flow field for enhancing hydrothermal performance of PEMFC: Optimization and analysis

A rational cathode flow field optimization design plays a key role in enhancing the overall performance of proton exchange membrane fuel cell (PEMFC). In this study, a complementary cathode flow field is proposed, which achieves structure-function dual complementarity by ingeniously integrating recesses and blocks. The complementary stepped flow field is further derived based on the flow field characteristics. A three-dimensional numerical PEMFC model is developed to comparatively investigate the effects of flow field geometry parameters on mass transfer and drainage performance. The complementary effects of recesses and blocks are thoroughly analyzed. The results demonstrate that recesses effectively mitigate the high pressure drop caused by blocks, while blocks promote more gas diffusion into recesses. Recesses address the defect of disordered water migration induced by blocks, while blocks compensate for the shortcoming of difficult water discharge in recesses after water collection. Compared with the conventional straight channel (SC), the net power densities of the recess-only and block-only channels increase by 12.56% and 3.92%, respectively, while that of the novel channel increases by 17.25%, even exceeding the sum of the previous two increases. RB2-6 is the best-performing complementary cathode flow field. At the center lines of channel and rib, compared with SC, RB2-6 improves the average O₂ concentration by 17.27% and 430.58%, respectively, and reduces the average water saturation by 16.92% and 17.92%, respectively. ST3 based on RB2-6 is the best-performing complementary stepped flow field, achieving a 38.78% increase in net power density compared with SC and more uniform species distribution.