Water based proton conductors

Boldly stated, the objectives in the design of excellent water-based proton conductors are to (1) charge them up with extra protons as much as possible (2) ensure... 

Chapter 2 dwells on all aspects of the structure and functioning of polymer electrolyte membranes. The detailed treatment is limited to water-based proton conductors, as, arguably, water is nature s favorite medium for the purpose. A central concept in this chapter is the spontaneous formation of ionomer bundles. It is a linchpin between polymer physics, macromolecular self-assembly, phase separation, elasticity of ionomer walls, water sorption behavior, proton density distribution, coupled transport of protons and water, and membrane performance. 

Bhide, S.V. and Virkar, A.V., Stability of BaCeOj-based proton conductors in water-containing atmospheres, / Electrochem. Soc., 146, 2038-2044 (1999). 

The success of widening the operating temperature for water-based proton conduction system has so far not been matched in the field of intrinsically dry proton conductors. Although interesting developments were reported in the field of polymers having tethered imidazole groups [31-34], these and other approaches based on phosphonated polymers, either in their pure form or as acid-base copolymers or blends, show conductivity values, which are at least an order of magnitude too low [34—36]. 

Polyvinyl fluoride (PVF) has been sulfonated by treatment of PVF films with chlorosulfonic acid. These materials provide new types of polymer-based proton conductors and the state of water in sulfonated PVF membranes has been studied by FTIR spectroscopy. ... 

A second commercially available electrolyzer technology is the solid polymer electrolyte membrane (PEM). PEM electrolysis (PEME) is also referred to as solid polymer electrolyte (SPE) or polymer electrolyte membrane (also, PEM), but all represent a system that incorporates a solid proton-conducting membrane which is not electrically conductive. The membrane serves a dual purpose, as the gas separation device and ion (proton) conductor. High-purity deionized (DI) water is required in PEM-based electrolysis, and PEM electrolyzer manufacturer regularly recommend a minimum of 1 MQ-cm resistive water to extend stack life. 

In the presence of water this polyelectrolyte is an excellent protonic conductor, although it suffers some degradation in a working fuel cell. Probably the most successful polyelectrolytes developed so far are based on perfluorinated polymers, the first of which was Nafion , with the structure ... 

Since the 1980 s, a new type of humidity sensor, based on a solid electrolyte, has been under development. The sensor uses a protonic conductor as a base component and makes a galvanic cell of a water vapor gas concentration type. When the characteristics of this new type of sensor are compared with conventional humidity sensors, two representative advantages of this sensor are seen. The sensor output is an EMF change, and is suitable for continuous operation with a fast response. The sensor can operate at higher temperatures, because the solid electrolyte is stable even at elevated temperatures. These features are expected to accelerate the development of this type of sensor. The base material is a perovskite-type strontium cerate SrCeOa. The pure cerate is not a protonic conductor. 

In a humidity sensor, ytterbium doping into the rare-earth cerium base material is the key point to obtaining a suitable solid electrolyte for humidity detection. Cerium site substitution of the ytterbium trivalent cation produces holes in the cerate and it becomes an excellent protonic conductor in the presence of hydrogen or water vapor. Rare-earth doping in the cerate is essential to obtain a solid electrolyte for the humidity sensor. 

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