(641i) AC Impedance Spectroscopy Analysis of Improved Proton Exchange Membrane Fuel Cell Operation Via Direct Inlet Gas Humidity Control

Efficient management of water is a major factor toward improving operation of Proton Exchange Membrane (PEM) Fuel Cells. The amount of water in various PEM fuel cell components will impact a variety of microprocesses that involve the transport and reaction of protons, electrons, and molecular species critical to efficient fuel cell operation. Electrochemical impedance spectroscopy (EIS) may be used to help resolve and quantify the relative magnitude of these processes in the operating fuel cell. This study is aimed at using EIS to evaluate how a new method of precisely controlling fuel cell humidity may be used to optimize the performance of a PEM fuel cell. The method involves humidity sensing and control of the reactant gas streams immediately before entry into the fuel cell stack. The interaction between various relative anode/cathode inlet humidity levels (wet/wet, dry/wet, wet/dry, and dry/dry) and stoichiometry will be investigated at a given temperature. Data obtained from this study is compared and fitted to equivalent circuit models proposed in literature to test their validity and to quantify fundamental process parameters.