Method to Enhance Fuel Cell Powertrain System Robustness by Reducing Cathode Potential during Start-Up Condition

This study investigates a system and a method to enhance fuel cell vehicle robustness during vehicle start/stop cycle by mitigating cathode half-cell potential spikes. Multiple dynamic hydrogen reference electrodes were installed in the fuel cell under test to observe changes of anode and cathode half-cell potentials during simulated system startup and shutdown conditions. Multiple reference electrodes were used to measure localized anode and cathode half-cell potentials in an active area. A 1.4-1.8 V half-cell potential spike at the cathode in the startup condition was observed due to a hydrogen/air boundary formed within the anode flow field. Various system solutions have been studied to contain the cathode half-cell potential spikes, such as purging with inert gas, or inserting a shunt resistor as a shorting component between the anode and the cathode. In this study, a method of connecting an electrical load prior to flowing hydrogen fuel to the cell was tested. Pre-loading the fuel cell proved to be an effective method to reduce the cathode potential spike during simulated startup conditions. The hypothesis is that the load current inhibits hydrogen oxidation reaction at anode. The effectiveness of the potential spike reduction varies with the level of load current and design of stack/cell. Optimization of load current control will be necessary to implement this method into a practical fuel cell system. An advantage of this method is that any additional component, such as a shunt resistor, is not required in the system.