Measurement of local electrode potentials in operating fuel cells can provide important information about spatial variations in performance and durability. These measurements are useful for improved understanding of localized effects associated with contaminants, startup/shutdown, electrode irregularities, membrane cracks/holes, and fuel starvation. Accurate measurement of local electrode potentials requires incorporation of multiple reference electrodes into the fuel cell hardware. By connecting external reference electrodes to the outside of the MEA using ionomer salt bridges, local potential measurements can be obtained without disturbing cell operation [1].

Contaminants such as CO can cause strong localized electrode poisoning in operating fuel cells. Incorporation of multiple reference electrodes has enabled measurement of the distribution of anode losses in a fuel cell exposed to CO, as depicted in Fig. 1. Similar techniques can be used to measure and deconvolute losses associated with the anode and cathode. However, robust ionic connectivity between the MEA and the external reference electrodes is required to enable quantitative potential measurements. Excessive impedance in this ion-conducting pathway can result in slow response times, reference potential drift, and non-quantitative measurements. This work describes improved techniques for integrating external reference electrodes, allowing more accurate quantification of local electrode potentials.

Fig. 1. Change in cell voltage and local anode potential (vs SHE) during exposure to CO gas (~400 s) and removal of CO (~1,800 s).

References

1. E. Brightman, G. Hinds, Journal of Power Sources 267 (2014) 160-170.

Acknowledgements

This research is sponsored by the Fuel Cell Technologies Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy and the U.K. National Measurement System.