Polymer electrolytes structures

Both temperature and pressure have a significant influence on cell performance the impact of these parameters will be described later. Present cells operate at 80°C, nominally, 0.285 MPa (30 psig) (5), and a range of 0.10 to 1.0 MPa (10 to 100 psig). Using appropriate current collectors and supporting structure, polymer electrolyte fuel cells and electrolysis cells should be capable of operating at pressures up to 3000 psi and differential pressures up to 500 psi (4). 

Gasa, J. V. Weiss, R. A. Shaw, M. T., Structured polymer electrolyte blends based on suKonated polyetherketoneketone (SPEKK) and poly(ether imide) (PEI),/. Membr. S d.,320,215-223 (2008). 

Figure 7. Structures of dual-phase polymer electrolytes. Reprinted from T. Ichino, M. Matsumoto, Y. Take-shita, J. S. Rutt, S. Nishi, Electrochim. Acta. 40, 2265-2268, Copyright 1995, with kind permission of Elsevier Science Ltd. The Boulevard, Langford Lane, Kindlington 0X5 1GB, UK.

Research and development into polymer electrolyte battery systems continues, yet many unsolved and controversial issues, particularly relating to the inadequate understanding and control of ion dissociation and the relative mobilities of the ions, remain. Modem computational resources now allow the structures of complex systems such as polymer electrolytes to be simulated and evaluated. Computer simu-... 

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. 

Figure 4.1 Schematic of the atomic structure of the active three-phase interface between the metal particle that catalyzes the reaction, the carbon support necessary to conduct electrons, and the polymer electrolyte and solution necessary to conduct protons for electrocatalytic systems.

A variety of organoboron polymer electrolytes were successfully prepared by hydroboration polymerization or dehydrocoupling polymerization. Investigations of the ion conductive properties of these polymers are summarized in Table 7. From this systematic study using defined organoboron polymers, it was clearly demonstrated that incorporation of organoboron anion receptors or lithium borate structures are fruitful approaches to improve the lithium transference number of an ion conductive matrix. 

A new electrofluorescent switch was prepared with an electroactive fluorescent tetrazine blend of polymer electrolyte <06CC3612>. The structure and magnetic properties of the stable oxoverdazyl free radical 6-(4-acetamidophenyl)-1,4,5,6-tetrahydro-2,4-dimethyl-... 

Carbon is unique among chemical elements since it exists in different forms and microtextures transforming it into a very attractive material that is widely used in a broad range of electrochemical applications. Carbon exists in various allotropic forms due to its valency, with the most well-known being carbon black, diamond, fullerenes, graphene and carbon nanotubes. This review is divided into four sections. In the first two sections the structure, electronic and electrochemical properties of carbon are presented along with their applications. The last two sections deal with the use of carbon in polymer electrolyte fuel cells (PEFCs) as catalyst support and oxygen reduction reaction (ORR) electrocatalyst. 

Antoine et al. [28] inveshgated the gradient across the CL and found that the Pt utilization was dependent on the CL porosity. In a nonporous CL, catalyst utilization was increased through the preferential locahon of Pt close to the gas diffusion layer in a porous CL, catalyst utilization efficiency was increased through the preferential location of Pt close to the polymer electrolyte membrane. In PEM fuel cells, fhe CL has a porous structure, and better performance is expected if higher Pf loading is used af preferential locahons close to the membrane/catalyst layer interface. 

Bose, A. B., Shaik, R., and Mawdsley, J. Optimization of the performance of polymer electrolyte fuel cell membrane electrode assemblies Roles of curing parameters on the catalyst and ionomer structures and morphology. Journal of Power Sources 2008 182 61-65. 

Kamarajugadda, S., and Mazumder, S. Numerical investigation of the effect of cathode catalyst layer structure and composition on polymer electrolyte membrane fuel cell performance. Journal of Power Sources 2008 183 629-642. Krishnan, L., Morris, E. A., and Eisman, G. A. Pt black polymer electrolyte-based membrane-based electrode revisited. Journal of the Electrochemical Society 2008 155 B869-B876. 

Passalacqua, E., Lufrano, R, Squadrito, G., Patti, A., and Giorgi, L. Influence of the structure in low-Pt loading electrodes for polymer electrolyte fuel cells. Electrochimica Acta 1998 43 3665-3673. 

Bolwin, K., Giilzow, E., Bevers, D., and Schnurnberger, W. Preparation of porous electrodes and laminated electrode-membrane structures for polymer electrolyte fuel cells (PEFCs). Solid State Ionics 1995 77 324-330. 

Kamarajugadda, S., and Mazumder, S. Numerical investigation of the effect of cathode catalyst layer structure and composition on polymer electrolyte membrane fuel cell performance. Journal of Power Sources 2008 183 629-642. 

Ding, J. F, Chuy, C. and Holdcroft, S. 2002. Solid polymer electrolytes based on ionic graft polymers Effect of graft chain length on nano-structured, ionic networks. Advanced Functional Materials 12 389-394. 

P. Sinha, P. Mukherjee, and C. Y. Wang. Impact of GDL structure and wettability on water management in polymer electrolyte fuel cells. Journal of Materials Chemistry 17 (2007) 3089-3103. 

Schematic depiction of seven-layer structure and basic processes in polymer electrolyte fuel cells under standard operation with hydrogen and oxygen.

Schematic depiction of the structural evolution of polymer electrolyte membranes. The primary chemical structure of the Nafion-type ionomer on the left with hydrophobic backbone, side chains, and acid head groups evolves into polymeric aggregates with complex interfacial structure (middle). Randomly interconnected phases of these aggregates and water-filled voids between them form the heterogeneous membrane morphology at the macroscopic scale (right).

Physical models of fuel cell operation contribute to the development of diagnoshc methods, the rational design of advanced materials, and the systematic ophmization of performance. The grand challenge is to understand relations of primary chemical structure of materials, composition of heterogeneous media, effective material properties, and performance. For polymer electrolyte membranes, the primary chemical structure refers to ionomer molecules, and the composition-dependent phenomena are mainly determined by the uptake and distribuhon of water. 

M. Eikerling, A. A. Kornyshev, and E. Spohr. Proton-conducting polymer electrolyte membranes Water and structure in charge. Advances in Polymer Science 215 (2008) 15-54. 

The structures and charge transport mechanisms for polymer electrolytes differ greatly from those of inorganic solid electrolytes, therefore the purpose of this chapter is to describe the general nature of polymer electrolytes. We shall see that most of the research on new polymer electrolytes has been guided by the principle that ion transport is strongly dependent on local motion of the polymer (segmental motion) in the vicinity of the ion. 

In the broad use of the word polymer, ion-containing polymers are ubiquitous. They include inorganic substances such as silicate and borosilicate glasses discussed in Chapter 4, most biopolymers, solvent-swollen synthetic ion exchangers and some synthetic structural polymers. With few exceptions, these exhibit the characteristic feature of an electrolyte, ion mobility. In this chapter we consider the group of synthetic... 

Poly(ethylene oxide) (usually abbreviated to PEO) has been the most intensively studied host polymer for polymer electrolytes and it serves as a prototype for the structural features in most of the more advanced polymer electrolyte hosts. It consists of —O—CHj—CHj— repeat units and occurs as a semicrystalline solid. The relative orientations of groups... 

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