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 experimental techniques and results include polarization curves and Electrochemical Impedance Spectroscopy (EIS) analy...

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Bibliographic Details
Published in:Energy (Oxford) 2021-04, Vol.221, p.119833, Article 119833
Main Authors: Iranzo, Alfredo, Navas, Sergio J., Rosa, Felipe, Berber, Mohamed R.
Format: Article
Language:English
Subjects:
Damköhler number
Diffusion
Electrochemical Impedance Spectroscopy
Electrochemistry
Electrode polarization
Electrolytes
Electrolytic cells
Fuel cells
Fuel technology
High Frequency Resistance
Nyquist plots
Oxygen
Oxygen diffusion
Polymer Electrolyte Membrane fuel cell
Polymers
Proton exchange membrane fuel cells
Relative humidity
Spectroscopy
Stoichiometry
Time constant
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Summary: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 experimental techniques and results include polarization curves and Electrochemical Impedance Spectroscopy (EIS) analysis of the fuel cell, where the time constants are determined from the analysis of the Distribution of Relaxation Times (DRT). EIS results are also used to determine the cell ohmic resistance, where High Frequency Resistance (HFR) values are calculated from the Nyquist plots. A wide range of operating conditions of the fuel cell are analysed, including back pressure (0.5 bar–1 bar), cell temperature (55 °C, 65 °C, 75 °C), reactant gases relative humidity (30%, 60%, 90%), cathode stoichiometry (λc 2.5–3.5), and oxygen concentration (air and pure oxygen). The effect of the operating conditions on the time constants are discussed, and Damköhler number is introduced and discussed. •Time constants are determined via Distribution of Relaxation Times (DRT).•Electrochemical and oxygen diffusion characteristic times are determined.•Results for a technical-size cell 50 cm2 provided for the first time.•Influence of a range of conditions are discussed (i, P, T, RH, λc, oxygen concentration).
ISSN:0360-5442
1873-6785
DOI:10.1016/j.energy.2021.119833