Spectroscopy, polymer electrolytes

Infrared and Raman spectroscopy have been very useful in the study of polymer electrolytes because they provide indications of cation-anion... 

Magnetic Resonance Imaging and Tunable Diode Laser Absorption Spectroscopy for In-Situ Water Diagnostics in Polymer Electrolyte Membrane Fuel Cells... 

These examples and the general subjects mentioned above illustrate that ion conduction and the electrochemical properties of solids are particularly relevant in solid state ionics. Hence, the scope of this area considerably overlaps with the field of solid state electrochemistry, and the themes treated, for example, in textbooks on solid state electrochemistry [27-31] and books or journals on solid state ionics [1, 32] are very similar indeed. Regrettably, for many years solid state electrochemistry/solid state ionics on the one hand, and liquid electrochemistry on the other, developed separately. Although developments in the area of polymer electrolytes or the use of experimental techniques such as impedance spectroscopy have provided links between the two fields, researchers in both solid and liquid electrochemistry are frequently not acquainted with the research activities of the sister discipline. Similarities and differences between (inorganic) solid state electrochemistry and liquid electrochemistry are therefore emphasized in this review. In Sec. 2, for example, several aspects (non-stoichiometry, mixed ionic and electronic conduction, internal interfaces) are discussed that lead to an extraordinary complexity of electrolytes in solid state electrochemistry. 

Figure 3.15. Schematic representation of the correlation between fuel cell impedance and polarization curve. (Modified from [23], with kind permission from Springer Science+Business Media Journal of Applied Electrochemistry, Characterization of membrane electrode assemblies in polymer electrolyte fuel cells using a.c. impedance spectroscopy, 32(8), 2002, 859-63, Wagner N. Figure 4.)...

Springer TE, Zawodzinski TA, Wilson MS, Gottesfeld S (1996) Characterization of polymer electrolyte fuel cells using AC impedance spectroscopy. J Electrochem Soc 143(2) 587-99... 

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... 

Andreaus B, McEvoy AJ, Scherer GG (2002) Analysis of performance losses in polymer electrolyte fuel cells at high current densities by impedance spectroscopy. Electrochim Acta 47 2223-9... 

Kuhn H, Andreaus B, Wokaun A, Scherer GG (2005) Electrochemical impedance spectroscopy applied to polymer electrolyte fuel cells with a pseudo reference electrode arrangement. Electrochim Acta 51 1622-8... 

Schneider I, Scherer G (2006) Fast locally resolved electrochemical impedance spectroscopy in polymer electrolyte fuel cells. European patent EP 1691438 A1... 

Wang X, Hsing IM, Leng YJ, Yue PL (2001) Model interpretation of electrochemical impedance spectroscopy and polarization behavior of H2/CO mixture oxidation in polymer electrolyte fuel cells. Electrochim Acta 46(28)4397-405... 

Forsyth, M., Meakin, P., MacFarlane, D.R., Hill, A.J. (1993) Positron annihilation lifetime spectroscopy as a probe of free volume in plasticized solid polymer electrolytes . Electrochimica Acta, 40(13), 2349. 

The polysiloxanes were characterized by Fourier transform-IR (FTIR) spectroscopy, H and Si NMR spectrometry, and by GPC. AC conductivities of the polymer electrolytes were measured under dry helium by using an automatic capacitance bridge (General Radio Corporation). Glass transition (Tg) and melt (TJ temperatures were recorded on a differential scanning calorimeter (Perkin Elmer DSC-4). More detailed experimental procedures are published elsewhere (9, 12). 

The material of PtRu alloy exhibits good properties for CO tolerance in polymer electrolyte membrane fuel cells (PEMFC) [68] and has been studied extensively in recent years [69]. Particular interest has been focused on the application of the PtRu alloy materials as anodes in methanol fuel cells (MFC) for electric vehicles [70]. The most convenient way to alter the surface composition of a PtRu alloy is to employ the electrochemical co-deposition method in the preparation of the alloy. Richcharz and co-workers have studied the surface composition of a series of PtRu alloys using X-ray photoelectron spectroscopy (XPS) and low-energy ion spectroscopy (LFIS)... 

We have completed experiments label the ionic domains. We have found evidence of a precipitation phenomenon of particles of iron oxide or hydroxide when an iron form of membrane was exchanged by different other ions like K+, Na+, etc. We therefore have analyzed these particles by different techniques -like X rays, Mossbauer spectroscopy, magnetic measurements and electron microscopy- with two goals in mind. First of all the formation of ultra thin particles is very important in different domains and especially in catalysis when these membranes are used in the solid polymer electrolyte process. Second, we expect some correlation between the sizes and distribution of precipitates with the starting ionic domains. 

This review deals with several types of polymer hosts that have been investigated. These include polyethylene oxide and its several modified forms, comb like polymers such as polyacrylates and inorganic polymers such as polyphosphazenes and polysiloxanes. Various instrumental techniques have been employed in the structural characterization of polymer electrolytes. The structural information obtained from methods such as Extended X-ray Absorption Fine Structure (EXAFS), X-ray diffraction methods, vibrational spectroscopy and nuclear magnetic resonance (NMR) have also been discussed. 

Because of the resistance to ion flow at the electrode-electrolyte interface, normal measurement of total ionic conductivity is not possible in polymer electrolytes. In order to overcome this problem the conductivity measurements are carried out by the ac impedance spectroscopy method, which minimizes the effects of cell polarization. The measurements are often made with the electrolyte sandwiched between a pair of electrochemically inert electrodes made of platinum or stainless steel. The detailed methodology of impedance spectroscopy is reviewed thoroughly elsewhere [45-47]. 

In general the effect of the added organic plasticizer appears to increase the free volume of the polymer thereby decreasing the Tg [93] and or reducing the content of the crystalline phase in PEO [83] and also to effect the ionic association in the polymer electrolytes [81]. Many of these effects have been studied by use of a variety of experimental methods such as IR spectroscopy, DSC, EXAFS, X-ray diffraction, NMR, conductivity studies, viscosity measurements etc. [81, 90,93-103]. The effects of the plasticizers on the conductivity behavior of PEO polymer electrolytes along with the conductivity data of other PEO-polymer electrolytes discussed above are summarized in Table 2. 

The question of the molecular level structure of polymer electrolytes and its relevance to understanding ionic conductivity has captured the attention of many researchers. This aspect has been investigated mainly by X-ray methods, NMR and vibrational spectroscopy. In the following a brief summary of these investigations is presented. 

Solid-state NMR spectroscopy has been used to study polymer electrolytes [27, 259-266]. Among the various nuclei that have been used as probes 7Li and 23Na have received maximum attention. However, the quadrupolar nature of these nuclei compounded with the solid state of the sample result in considerable line broadening of the NMR signal. Thus, a lot of valuable information pertaining to the structure of polymer electrolytes is not accessible. However, an analysis of the linewidths and the spin lattice relaxation times of the nuclei affords considerable information on the nature of the ions present in a polymer electrolyte. 

Polu, A.R., Kumar, R. Impedence spectroscopy and ETIR studies of PEG based polymer electrolytes. E- J. Chem. 2011, 8 (1), 347-353. 

Polymer electrolyte membrane Polymer electrolyte membrane fuel cell Pulse field gradient NMR spectroscopy Perfluorosulfonic acid ionomer... 

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