Determination of time constants of diffusion and electrochemical processes in Polymer Electrolyte Membrane Fuel Cells

This work presents an experimental analysis of the time constants associated to diffusion and electrochemical processes in a 50 cm2 Polymer Electrolyte Membrane (PEM) fuel cell. The techniques results include polarization curves Electrochemical Impedance Spectroscopy (EIS) cell, where are determined from Distribution Relaxation Times (DRT). EIS also used determine cell ohmic resistance, High Frequency Resistance (HFR) values calculated Nyquist plots. A wide range operating conditions analysed, including back pressure (0.5 bar–1 bar), temperature (55 °C, 65 75 °C), reactant gases relative humidity (30%, 60%, 90%), cathode stoichiometry (λc 2.5–3.5), oxygen concentration (air pure oxygen). effect on discussed, Damköhler number is introduced discussed.