Experimental and numerical investigation of the reverse current evolution during the start-up of a fuel cell

The transient reverse current distributions with high local potentials inside the proton exchange membrane fuel cell stack during the start-up process are critical to the performance degradation and lifetime. In this work, the transient reverse current distributions under different start-up conditions are tested with a self-designed segmented fuel cell device. Validated by the experimental results, a transient three-dimensional coupled fuel cell model is developed to investigate the multi-physical behaviors during the start-up process. As the open circuit voltage is being established, the “internal current surge” phenomenon is observed by the segmented cell test and reproduced by the transient model. The cathode local potential could reach up to 1.68 V around anode outlet and the high local potential lasts longer as the segment location gets closer to the anode outlet. The cathode catalyst carbon support around anode outlet experiences the most severe corrosion during the start-up process leading to nonuniform performance degradation. The increased H2 flow rate could reduce the local reverse coulombic charge by carbon oxidation reaction and narrow the reverse current affected area to alleviate local performance loss. Comprehensive understanding of the transient reverse current evolution and coulombic charge composition is beneficial to improve the start-stop control strategy of fuel cell for prolonged lifetime.