Electrochemical Impedance Spectroscopy in PEM Fuel Cells Fundamental
Fuel cells, as environmentally-friendly power generation devices, have been fully recognized by scientists, governments, and the public as a unique solution to several of the most important issues that we face today: diminishing supplies of fossil fuels,
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DST: HySA Infrastructure Center of Competence, Faculty of Natural Science 2 School of Electrical, Electronic and Computer Engineering, North-West University, Potchefstroom, South Africa Email: [email protected]
Kenny Uren, George van Schoor School of Electrical, Electronic and Computer Engineering North-West University Potchefstroom, South Africa
Abstract—In this paper the losses of a proton exchange membrane (PEM) single cell electrolyser were investigated. The ohmic, activation and mass transfer losses are the most prominent losses in a PEM electrolyser. The Electrochemical Impedance Spectroscopy (EIS) method was applied to identify these losses. A parametric study of each loss component was performed by changing a component or condition responsible for the loss. The membrane thickness was varied in the Membrane Electrode Assembly (MEA) to identify the ohmic loss and the temperature was changed to capture the activation loss. Two different diffusion media were used to investigate the mass transfer effect. The results were confirmed with polarisation curves and Tafel plots.
Keywords: Hydrogen, Electrochemical Impedance Spectroscopy (EIS), Proton Exchange Membrane (PEM), electrolyser
I. I NTRODUCTION A total of 81% of the world energy economy is based on fossil fuel resources [1]. The approaching end of life and harmful emissions produced by burning fossil fuels focusses research on hydrogen as an energy source. Hydrogen has the unique qualities as an energy source: An abundant source of hydrogen is found in water. The efficiency of hydrogen production through water electrolysis is high. Hydrogen is also environmentally compatible since in its production, storage, transportation and end use it does not produce any pollutants [2]. Three types of electrolyser technologies currently exist. Proton Exchange Membrane (PEM) electrolysers, Alkaline electrolyser and Solid-Oxide electrolysers SOEs). SOEs are developed to operate at high temperatures typically around 850◦ C. Typical applications for SOEs will be to operate in combination with nuclear plants or other plants where extra heat is available at low cost. Alkaline and PEM electrolysers are well established for hydrogen production at lower temperatures. The PEM electrolyser offers some advantages over the alkaline electrolyser: higher current densities, a high degree of hydrogen purity, a higher discharge pressure, smaller mass and the possibility of converting into a fuel cell [3]. The PEM electrolyser consists of a solid proton conducting polymer which acts as a gas-impermeable membrane. As a 978-1-4673-4569-9/13/$31.00 ©2013 IEEE
Dmitri Bessarabov DST: HySA Infrastructure Center of Competence Faculty of Natural Science North-West University Potchefstroom, South Africa
benefit the PEM electrolyser is safe and reliable [3]. PEM electrolyser reliability is very high and some electrolysers have reached over 100 000 hours of operation without failure [4]. In previous work Choi et al. [5] considered the cell voltage to be the sum of the open voltag
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