Mass-transport resistances of acid and alkaline ionomer layers: A microelectrode study part 1 - Microelectrode development

The use of microelectrodes to study localized mass-transport phenomena in fuel-cell catalyst layers is an increasingly valuable tool. However, existing microelectrode cells have been used in static, equilibrated environment modes with poorly controlled interfaces. In this work, we present a microelectrode cell design that expands the experimental space addressable by microelectrodes to include mechanical pressure, gas flow and ionomer medium, and experimental throughput. The feasibility of the design is examined for fuel-cell reactions, with oxygen reduction currents independent of mechanical pressure and gas flowrate. Finally, cell equilibration time and IR drop across the electrolyte are estimated. The new cell design is robust and provides a consistent base from which to perform more complicated studies examining mass-transport properties of ionomers and/or the electrochemical reaction kinetics of hydrogen oxidation and oxygen reduction