In-Situ Diagnostics of PEFCs

Polymer electrolyte fuel cells (PEFCs) are one of the most interesting alternatives for a pollution-free electrical energy production in many applications where a highly reliable source of electricity is needed. One of the major challenges in the development of PEFCs is to exploit the whole capacity that is inherent to a given membrane electrode assembly (MEA). In practice, certain obstacles remain to be overcome like local mass transport effects, non-uniformly manufactured MEAs, locally varying contact resistances, water management and temperature gradients. All these parameters lead to an inhomogeneous electrochemical activity over the electrode area. Consequently, a variation and a gradient of the current density over the cell area occurs which tends to result in inferior performance and low durability of a PEFC. For the determination of current density distribution different in-situ methods and measurement techniques are applied. Results can be used to improve cell components, to validate models and to detect inappropriate detrimental operating conditions of the fuel cell.