Polymeric electrolyte membrane

In recent years the concept of a fuel cell propulsion system has gained in attention as a result of the need to reduce the fossil fuel consumption and greenhouse gas emissions. Since the fuel cells suitable for vehicle application (polymeric electrolyte membrane fuel cells) are fuelled by hydrogen, and deliver power as long as fuel and air are supplied, they potentially can provide the range capabilities of an internal combustion engine when used in a power system, but with clean and quiet operation. Therefore, the fundamental benefit of this type of propulsion consists in the possibility to adopt pollution-free electric drive-trains, without the drive range limitations typical of traditional electric vehicles. 

C. Manea and M. Mulder, New polymeric electrolyte membranes based on proton donor-proton acceptor properties for direct methanol fuel cells. Desalination 147, 179-182 (2002). 

PBI membranes have been the critical components in high temperature polymeric electrolyte membrane fuel cells. PBI fuel cells tolerate much more impurities in the Hj fuel compared to low temperature fuel cells. Therefore, they are preferred in fuel cell systems where the Hj supplies are from reformers converting other fuels to Hj. PBI fuel cells are also suitable for combined heat and power fuel cell systems. In other applications, PBI membranes have been successfully demonstrated to purify Hj while pumping it against a high pressure. The technology can be applied... 

Boroxine ring-containing polymers have found extensive use in the development of polymeric electrolyte materials used in ion-selective transport membranes. Matsumi and Ohno cover this area in Chapter 6 of this book. 

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).

Some of the most useful polyphosphazenes are fluoroalkoxy derivatives and amorphous copolymers (11.27) that are practicable as flame-retardant, hydrocarbon solvent- and oil-resistant elastomers, which have found aerospace and automotive applications. Polymers such as the amorphous comb polymer poly[bis(methoxyethoxyethoxy)phosphazene] (11.28) weakly coordinate Li " ions and are of substantial interest as components of polymeric electrolytes in battery technology. Polyphosphazenes are also of interest as biomedical materials and bioinert, bioactive, membrane-forming and bioerodable materials and hydrogels have been prepared. 

The development of transparent polymer electrolyte membrane from the bi-continuous-microemulsion polymerization of 4-vinylbenzene sulfonic acid Hthium salt (VBSIi), acrylonitrile and a polymerizable non-ionic surfactant, co-methoxypoly(ethylene oxide)4o-undecyl-a-methacrylate (Ci-PEO-Cn-MA-40) was reported in 1999 [94,95]. The ionic conductivities of the polymer electro-... 

Many different kinds of fuel cells are presently known, most of them suitable for high-temperature applications— for details see Ref. [101]. The polymeric proton-conducting membranes (polymer electrolyte membranes PEM) are however suitable for low temperamre operations (<100°C) and have the advantage of low weight. 

Figure 42.2 shows a hypothetical polymeric NF membrane with carboxylic groups attached to the surface of the membrane, which is brought in contact with an aqueous solution of electrolytes. The presence of dissociated carboxylic groups on the membrane surface causes the occurrence of membrane charge. 

The lonomeric Membrane of the Polymeric Electrolyte Fuel Cell Summary. 270... 

The development of new polymeric materials for polymer electrolyte fuel cell is one of the most active research areas, aiming at the new energy sources for electric cars and other devices. The mainstream of the material research for fuel cell is perfluoroalkyl sulfonic acid membranes such as Nafion, Acipex, and Flemion. The most well-known one is Nafion of Du Pont, which is derived from copolymers of tetrafluoro-ethylene and perfluorovinyl ether terminated by a sulfonic acid group.Protons, when dissociated from the sulfonic acid groups in aqueous environment, become mobile and the membrane becomes a proton conducting electrolyte membrane. 

The proton exchange membrane - also known as polymer electrolyte membrane (PEM) - fuel cell uses a polymeric electrolyte. The protonconducting polymer forms the heart of each cell electrodes, usually made of porous carbon with catalytic platinum incorporated into them, are bonded to either side of the electrolyte to form a one-piece membrane-electrode assembly (MEA). The following are some key advantages that make PEMs such a promising technology for the automotive market ... 

---