Electrical Circuit Analysis of CO Poisoning in High-Temperature PEM Fuel Cells for Fault Diagnostics and Mitigation

High-temperature proton exchange membrane (HTPEM) fuel cells are able to withstand a substantial amount of CO poisoning while still maintaining stable output. High concentrations of CO will however degrade performance and can lead to instability. This paper presents a detailed study on the impact of CO poisoning on the performance of High-temperature PEM fuel cells and proposes a new method for mitigating the long term effects by using natural current profiles. A dedicated test setup was constructed to perform both steady state and dynamic analysis on the fuel cell under a wide range of operating conditions and variations in CO content. The drop in performance captured in the polarization curves is modeled using a simple circuit model with a dedicated fault element. The captured impedance spectra from the electrochemical impedance spectroscopy tests provide insight to the changes in the electrochemical circuit parameters that can be used to diagnose the extent of CO poisoning. Possible load control strategies that can reverse the CO poisoning is explored and the optimal profile is experimentally determined along with the long term effects.