An examination of the catalyst layer contribution to the disparity between the Nernst potential and open circuit potential in proton exchange membrane fuel cells

Research output: Contribution to journalArticlepeer-review


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External organisations

  • Toyota Motor Europe
  • Toyota Motor Corporation
  • University of Birmingham


The dependency of the Nernst potential in an operating proton exchange membrane fuel cell (PEMFC) on the temperature, inlet pressure and relative humidity (RH) is examined, highlighting the synergistic dependence of measured open circuit potential (OCP) on all three parameters. An alternative model of the Nernst equation is derived to more appropriately represent the PEMFC system where reactant concentration is instead considered as the activity. Ex situ gas diffusion electrode (GDE) measurements are used to examine the dependency of temperature, electrolyte concentration, catalyst surface area and composition on the measured OCP in the absence of H2 crossover. This is supported by single-cell OCP measurements, wherein RH was also investigated. This contribution provides clarity on the parameters that affect the practically measured OCP as well as highlighting further studies into the effects of catalyst particle surrounding environment on OCP as a promising way of improving PEMFC performance in the low current density regime.


Original languageEnglish
Article number965
Number of pages15
Issue number8
Publication statusPublished - 12 Aug 2021


  • Nernst potential, open circuit potential, catalyst layer, OCP, OCV, PEMFC