Electrochemical impedance spectroscopy cell membrane

Jiang R, Kunz HR, Fenton JM (2005) Electrochemical oxidation of H2 and Hi/CO mixtures in higher temperature (Teen > 100°C) proton exchange membrane fuel cells electrochemical impedance spectroscopy. J Electrochem Soc 152(7) A1329-A1340... 

Electrochemical impedance spectroscopy is usually presented in electrochemistry handbooks [12-22], although such presentations are usually quite brief. There are few books on impedance in English [3, 23-26], one in Russian [27], one on differential impedance analysis [28], and many chapters on specific topics [29-72]. The first book [23] on the topic was edited by Macdonald and centered on solid materials the second edition [24] by Macdonald and Barsoukov was enlarged by including other applications. Recently, three new books, by Orazem and Tribollet [3], by Yuan et al. [26] on proton exchange membrane fuel cells (PEM EC), and by Lvovich [25], have been published, while that by Stoynov et al. [27] was never translated into English. A third edition of the book by Macdonald and Barsoukov is in preparation. However, not all aspects of EIS are presented, and these books are not complete in the presentation of their applications. Plenty of review articles on different aspects of impedance and its applications have been published however, they are very specific and can usually be used only by readers who aheady know the basics of this technique. A Scopus search for electrochemical impedance spectroscopy to the end of 2012 comes up with 18,000 papers, most of them since 1996. 

The fuel cell was characterized for different alkali concentrations and temperatures by current-voltage measurements [ V(i) or E(i) curves], short-term operations under load, electrochemical impedance spectroscopy (EIS), and pH monitoring. The passage of ethanol through the membrane was determined by redox titration of the cathodic exhaust. 

Usually, the starting point of model derivation is either a physical description along the channel or across the membrane electrode assembly (MEA). For HT-PEFCs, the interaction of product water and electrolyte deserves special attention. Water is produced on the cathode side of the fuel cell and will either be released to the gas phase or become adsorbed in the electrolyte. As can be derived from electrochemical impedance spectroscopy (EIS) measurements [14], water production and removal are not equally fast Water uptake of the membrane is very fast because the water production takes place inside the electrolyte, whereas the transport of water vapor to the gas channels is difiusion limited. It takes several minutes before a stationary state is reached for a single cell. The electrolyte, which consists of phosphoric add, water, and the membrane polymer, changes composition as a function of temperature and water content [15-18]. As a consequence, the proton conductivity changes as a function of current density [14, 19, 20). 

Various planar membrane models have been developed, either for fundamental studies or for translational applications monolayers at the air-water interface, freestanding films in solution, solid supported membranes, and membranes on a porous solid support. Planar biomimetic membranes based on amphiphilic block copolymers are important artificial systems often used to mimic natural membranes. Their advantages, compared to artificial lipid membranes, are their improved stability and the possibility of chemically tailoring their structures. The simplest model of such a planar membrane is a monolayer at the air-water interface, formed when amphiphilic molecules are spread on water. As cell membrane models, it is more common to use free-standing membranes in which both sides of the membrane are accessible to water or buffer, and thus a bilayer is formed. The disadvantage of these two membrane models is the lack of stability, which can be overcome by the development of a solid supported membrane model. Characterization of such planar membranes can be challenging and several techniques, such as AFM, quartz crystal microbalance (QCM), infrared (IR) spectroscopy, confocal laser scan microscopy (CLSM), electrophoretic mobility, surface plasmon resonance (SPR), contact angle, ellipsometry, electrochemical impedance spectroscopy (EIS), patch clamp, or X-ray electron spectroscopy (XPS) have been used to characterize their... 

Kim J-R, Yi JS, Song T-W (2012) Investigation of degradation mechanisms of a high-temperature polymer-electrolyte-membrane fuel cell stack by electrochemical impedance spectroscopy. J Power Sources 220 54-64... 

Zhu Y, Zhu WH, Tatarchuk BJ (2014) Performance comparison between high temperature and traditional proton exchange membrane fuel cell stacks using electrochemical impedance spectroscopy. J Power Sources 256 250-257... 

Kumagai, M., Myung, S.-T., Ichikawa, T. et al. 2010. Evaluation of polymer electrolyte membrane fuel cells by electrochemical impedance spectroscopy under different operation conditions and corrosion. Journal of Power Sources 195 5501-5507. 

Le Canut, J. M. Abouatallah. 2006. Detection of membrane drying, fuel cell flooding, and anode catalyst poisoning on PEMFC stacks by electrochemical impedance spectroscopy. /. Electrochemical Society 153 A857-A864. 

Gomadam, P. and Weidner, J. W. 2005. Analysis of electrochemical impedance spectroscopy in proton exchange membrane fuel cells. > 29, 1133-1151. 

In Chapter 1, Figure 1.4 shows a typical polarization curve of a PEM fuel cell. The voltage loss of a cell is determined by its OCV, electrode kinetics, ohmic resistance (dominated by the membrane resistance), and mass transfer property. In experiments, the OCV can be measured directly. If the ohmic resistance (Rm). kinetic resistance (Rt, also known as charge transfer resistance), and mass transfer resistance (Rmt) are known, the fuel cell performance is easily simulated. As described in Chapter 3, electrochemical impedance spectroscopy (EIS) has been introduced as a powerfiil diagnostic technique to obtain these resistances. By using the equivalent circuit shown in Figure 3.3, Rm, Rt, and R t can be simulated based on EIS data. 

In Chapter 3, electrochemical impedance spectroscopy (EIS) was introduced as a powerful technique for PEM fuel cell diagnosis. EIS measurement can be conducted at OCV and under load. The AECD of the ORR (fo ) can be calculated using Eqn (3.8), based on the simulated /f° (charge transfer resistance at the OCV for the ORR) from the Nyquist plot obtained by EIS that is shown in Fig. 3.12. The values of the membrane resistance (/fm), charge transfer resistance (/ t) and mass transfer resistance (/fmt) in a PEM fuel cell at different current densities can also be simulated using measured EIS, based on... 

The conductivity of the polymers was also measured using a galvanostatic four-point-probe electrochemical impedance spectroscopy technique [17]. A four-point-probe cell with two platinum foil outer current-carrying electrodes and two platinum wire inner potential-sensing electrodes was mounted on a Teflon plate. The schematic view of the cell is illustrated in Fig. 6.3. Membrane samples were cut into strips that were approximately 1.0 cm wide, 5 cm long, and 0.01 cm thick prior to mounting in the cell. 

Proton conductivities of fully hydrated membranes (24 h at ambient temperature in double deionized HjO) may be measured using two- or four-probe electrochemical impedance spectroscopy (EIS) at frequency 0.1-10 MHz with AC amplitude of 5 or 10 mV (Rg. 3.2). For good membrane-electrode contact the PEM is placed between two Hg or Pt electrodes in a sealed conductivity cell, thermostated at the desired T for about 5 h before measurements. It is advisable to perform the measurements with dry membranes from 20 up to 100°C in 10°C steps with wet membranes. Each sample should be measured 10 times and the average value of the impedance, R, used for calculating the proton conductivity o = d/RS (S/cm), where d is the membrane thickness, thus the distance between the electrodes. The results are sensitive to the specimen immersion depth, quality of deionized water, and electrode/membrane contact. Usually, the ionic conductivity correlates with the degree of sulf onation, 38. .82,83... 

Wagner N (2002) Characterization of membrane electrode assemblies in polymer electrolyte fuel cells using a.c. impedance spectroscopy. J Appl Electrochem 32(8) 859-63... 

Figure 4.33. Equivalent circuit of a catalyst layer [8]. (Reproduced by permission of the authors and of ECS—The Electrochemical Society, from Lefebvre MC, Martin RB, Pickup PG. Characterization of ionic conductivity within proton exchange membrane fuel cell gas diffusion electrodes by impedance spectroscopy.)...

Figure 5.9. AC impedance spectra of Nafion 115 membrane obtained by the two-probe cell method with different probe distances, at room temperature and under fully hydrated conditions [9], (Reproduced by permission of ECS—The Electrochemical Society, from Xie Z, Song C, Andreaus B, Navessin T, Shi Z, Zhang J, Holdcroft S. Discrepancies in the measurement of ionic conductivity of PEMs using two- and four-probe AC impedance spectroscopy.)...

Figure 6.49. In situ AC impedance spectroscopy at a frequency range of 3500 to 0.1 Hz at 0.91 A/cm2, 100% RH, and 30 psig pressure at 80°C, 100°C, and 120°C [44]. (Reproduced by permission of ECS—The Electrochemical Society, and of the authors, from Tang Y, Zhang J, Song C, Liu H, Zhang J, Wang H, MacKinnon S, Peckham T, Li J, McDermid S, Kozak P, Temperature dependent performance and in situ AC impedance of high temperature PEM fuel cells using the Nafionl 12 membrane.)...

The applications of impedance spectroscopy are not limited to the characterization of electrode properties. Sometimes it is desirable to investigate the properties of membranes, solutions, or dielectrics. For this kind of appKcation, ur-eiectrode cells provide the best results. Two reference electrodes are placed in the electrochemical cell between counter and working electrodes (Fig. 23c). The impedance measured depends purely on the properties of the electrolyte or membrane between the two reference electrodes, and the electrode properties are completely eliminated from the impedance spectrum. 

N. Wagner [2002] Characterization of Membrane Electrode Assemblies in Polymer Electrolyte Fuel Cells using a.c. Impedance Spectroscopy, J. Appl. Electrochem., 32, 859-863. 

Since a fuel cell is an electrochemical device, electrochemical mefliods are deemed to play important roles in characterizing and evaluating the cell and its components such as the electrode, the membrane, and the catalyst. The most popular eleetroehemical characterization methods include potential step, potential sweep, potential cycling, rotating disk electrode, rotating ring-disk eleetrode, and impedance spectroscopy. Some techniques derived from these methods are also used for fuel cell characterization. 

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