Operational Regime for Maximizing the Durability in Fuel Cell Stacks
Authors: Rice Cynthia A. , Swider-Lyons Karen 
Published: December 2024

Fuel cells have a dichotomy between high performance and long durability, which is further exacerbated by the requirement for high production scale manufacturing. To bridge the aforementioned disconnects, the fuel cell system’s operational controls must be optimized to protect the fuel cell stack from being exposed to conditions that would detrimentally impact the fuel cell stack durability. For instance, Toyota has shown that the fuel cell stack is protected from platinum electrocatalyst oxidation by limiting the upper voltage during idle to 0.85 V (Toyota).[1] The operational controls landscape that must be evaluated as a function of durability are inlet coolant temperature, coolant delta temperature across the stack, coolant temperature cycling and rate, reactant stoichiometry, inlet relative humidity (RH), RH cycling and rate, back pressure, material dependent water back diffusion, cathode catalyst loading, and the load profile and rate.
To better understand the impact of the fuel cell operational regime on durability, we evaluate the relative decay rates for multiple short stacks under limited stress tests: (ST1) mid power current density hold, (ST2) elevated coolant temperature/low RH load cycling (GM),[2] and (ST3) concurrently cycling coolant temperature/RH/load. The voltage decay rates are tracked over time to estimate stack lifetime. The stack voltages decrease over the time on test under all three stress test profiles, attributed to initial aging of the cathode catalyst. Polarization curves are used to evaluate decay rates intermittently during the applied stress tests, the decay rates are dependent on current densities in the polarization curve.
We find that the voltage decay rate is elevated within the kinetic region of the polarization curve and lower in the mas transport region. The most aggressive stress test is ST3, due to the combined coolant temperature/RH/load cycling.

Acknowledgments

This material is based upon work supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Hydrogen and Fuel Cell Technologies Office’s FY2020 H2@Scale New Markets FOA, Award Number DE-EE0009248. W. Gibbons (DOE Program Manager), R. Mukunda (LBL), D. Cullen (ORNL), and KC Neyerlin (NREL).
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