Influence of material properties of bipolar plates on power performances of proton exchange membrane fuel cell stacks

The material property of bipolar plates is extremely vital for thermal and energy management in power performance improvement of a proton exchange membrane fuel cell. The aim of this work is to reveal the influence of the material properties of bipolar plates on power performances of proton exchange membrane fuel cell stacks from detailed internal flow, electricity, heat and mass distribution characteristics. The power performances of large-scale proton exchange membrane fuel cell stacks consisted by two kinds of bipolar plates (the metal and the graphite bipolar plates) were evaluated experimentally. A three-dimensional coupled numerical simulation model for a stack cell was established and experimentally verified to reveal internal current density, heat and mass and potential distribution characteristics during electrochemical reaction by considering the material properties of bipolar plates. It was found that the power performance of the proton exchange membrane fuel cell stack consisted by the graphite bipolar plates was better than that of the metal bipolar plates. Cross-sectional distribution characteristics of the temperature, current density, ohmic heat source, hydrogen, oxygen and potential at corresponding interfaces for two kinds of bipolar plates were comparatively discussed. The mechanism of the superior power performance in the case of the graphite bipolar plates was revealed by a better distribution uniformity of the interfacial temperature and a lower contact resistance. The heat transfer entropy generation and the gases consumption in electrochemical reaction for different material properties of bipolar plates were assessed to compare the energy conversion degree.