Polymer electrolytes types

M. Tamura, K. Sanekata, Y. Higuchi and H. Miyake, Polymer electrolyte type fuel cell, Jpn. Pat. No. 3342726 I. Terada, Trend in development of ion exchange membrane for fuel cell, Kagaku Keizai (Chem. Econ.), 2001, 48(9), 78-83. 

M. Katoh, Y. Nishiki and S. Nakamatsu, Polym. electrolyte-type electrochemical ozone generator with oxygen cathode, J. Appl. Electrochem., 1994, 24, 489-494 ... 

The materials and stmcture of an RFC depend on the operating temperature (polymer electrolyte type or sohd oxide type), cell design (unitized or separate fuel ceU/electrolyzer units), and reactants (H2/O2, H2/CI2, etc.). 

Fuel Cell Stack Fuel cell Polymer electrolyte type... 

Depending on the materials used for the separation membrane, the ionic conductivity is different as is the temperature at which the desirable ionic conductivity is obtained. Fuel cells can be classified as alkaline, phosphate, molten carbonate, solid oxides, and polymer electrolyte types. These all exhibit different characteristics, and research and development have been focusing on these differences. Readers interested in these aspects of fuel cells are referred to the works by Fueki and Takahashi [1], and Takahashi [2]. Discharge characteristics of various fuel cells are shown in Fig. 2. [3]... 

To benefit from these advantages, it is now becoming clear that pure ionomer membranes are not suitable, and new types of proton-conducting membranes that work at temperatures higher than 100 °C have to be developed. There are currently three principal polymer electrolyte types proposed for high temperature PEMFCs ... 

Three types of electrochemical water-spHtting processes have been employed (/) an aqueous alkaline system (2) a soHd polymer electrolyte (SPE) and (J) high (700—1000°C) temperature steam electrolysis. The first two systems are used commercially the last is under development. 

Polymer electrolytes (Sec. 8), especially those which have been developed recently, combine several advantages of both types of electrolytes. They share sev-... 

Polymer lifetime, mapped for n-type silicon in contact with the polymer electrolyte, 497... 

The electrocatalytic oxidation of methanol has been widely investigated for exploitation in the so-called direct methanol fuel cell (DMFC). The most likely type of DMFC to be commercialized in the near future seems to be the polymer electrolyte membrane DMFC using proton exchange membrane, a special form of low-temperature fuel cell based on PEM technology. In this cell, methanol (a liquid fuel available at low cost, easily handled, stored, and transported) is dissolved in an acid electrolyte and burned directly by air to carbon dioxide. The prominence of the DMFCs with respect to safety, simple device fabrication, and low cost has rendered them promising candidates for applications ranging from portable power sources to secondary cells for prospective electric vehicles. Notwithstanding, DMFCs were... 

Furan was dimethoxylated to give 2,5-dihydro-2,5-dimethoxyfuran, using electrogenerated bromine molecules generated from bromide salts in electrolyte solutions [71]. This reaction was characterized in classical electrochemical reactors such as pump cells, packed bipolar cells and solid polymer electrolyte cells. In the last type of reactor, no bromide salt or electrolyte was used rather, the furan was oxidized directly at the anode. H owever, high consumption of the order of 5-9 kWh kg (at 8-20 V cell voltage) was needed to reach a current efficiency of 75%. 

Membrane-type fuel cells. The electrolyte is a polymeric ion-exchange membrane the working temperatures are 60 to 100°C. Such systems were first used in Gemini spaceships. These fuel cells subsequently saw a rather broad development and are known as (solid) polymer electrolyte or proton-exchange membrane fuel cells (PEMFCs). 

Incorporation into a Polymer Layer In recent years a new electrode type is investigated which represents a layer of conducting polymer (such as polyaniline) into which a metal catalyst is incorporated by chemical or electrochemical deposition. In some cases the specific catalytic activity of the platinum crystallites incorporated into the polymer layer was found to be higher than that of ordinary dispersed platinum, probably because of special structural features of the platinum crystallites produced within the polymer matrix. A variant of this approach is that of incorporating the disperse catalyst directly into the surface layer of a solid polymer electrolyte. 

Another factor also contributed to the appearance of new concepts in electrochemistry in the second half of the twentieth century The development and broad apphca-tion of hthium batteries was a stimulus for numerous investigations of dilferent types of nonaqueous electrolytes (in particular, of sohd polymer electrolytes). These batteries also initiated investigations in the held of electrochemical intercalation processes. 

II. Anion-Trapping-Type Organoboron Polymer Electrolytes via... 

Ion-conductive properties of anion-trapping-type organoboron polymer electrolytes was evaluated after adding lithium salts (Fig. 3). In these systems, ionic conductivity of 3.05 X 10 s 5.22 X 10 6Scm 1 was observed at 50°C. This indicates... 

A nion- Trapping- Type Organoboron Polymer Electrolytes 179... 

The lithium transference number (l,) of these organoboron polymer electrolytes was evaluated by combination of dc polarization and ac impedance methods, as reported by Evans et al44 (Table 1). The observed t+ at 30°C was 0.50-0.35, indicating that anions were significantly trapped in these systems. Owing to the stronger Lewis acidity of the alkylborane unit, alkylborane-type polymers showed relatively higher t+. 

Interestingly, the nonpolyether-type polymer electrolyte 7 showed a relatively high lithium transference number of 0.47 in the presence of LiTFSI. This is possibly due to the absence of strong binding of ether oxygen to the lithium cation. Moreover, anion trapping of the boron atom is not retarded by coordination of oxygen to the... 

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