Perfluorosulfonic acid modified

Harrison et al. (1988) have shown that GOD-modified platinum electrodes can be effectively protected from electrode fouling by dip-coating with a perfluorosulfonic acid polymer. The dip-coating formed a polymer layer of 2 pm thickness on the electrode. After 6 days of continuous in vitro measurement in whole blood at 37°C the sensitivity was decreased by only 6%. Interferences from electroactive anions were reduced due to the Donnan exclusion of these species. Nevertheless, differential measurements were necessary for complete elimination of interferents. 

Measurements of the 120, 214 and 295 duPont Nafion films and also fully converted ethylene diamine films are considered to be typical. The 120 polymer is a homogeneous film 10 mils thick of 1200 equivalent weight, (ew), perfluorosulfonic acid resin. The 214 and 295 films are each of 7 mils thick resin of 1150 ew having one surface facing the cathode that has been chemically modified to 1.5 mils depth, and having T-24 backing. The 295 films are the same as the 214 except that they are modified to a 1.5 mil depth and have T-900 backing (17) (18). 

Harmer, MA Sun, Q Michalczyk, MJ Yang, Z Unique silane modified perfluorosulfonic acids as versatile reagents for new solid-acid catalysts. Chem. Commun. 1997, 1803-1804. 

E.J. Hora and D.E. Maloney, Chemically Modified Nafion Perfluorosulfonic Acid Membranes as Separators in Chlor-Alkali CeXli, Abstract 441, Electrochemical Society Meeting, Atlanta, GA (1977). 

High-temperature proton exchange membrane fuel cells (HT-PEM fuel cells), which use modified perfluorosulfonic acid (PFSA) polymers [1—3] or acid-base polymers as membranes [4—8], usually operate at temperatures from 90 to 200 °C with low or no humidity. The development of HT-PEM fuel cells has been pursued worldwide to solve some of the problems associated with current low-temperature PEM fuel cells (LT-PEM fuel cells, usually operated at <90 °C) these include sluggish electrode kinetics, low tolerance for contaminants (e.g. carbon monoxide (CO)), and complicated water and heat management [4,5]. However, operating a PEM fuel cell at >90 °C also accelerates degradation of the fuel cell components, especially the membranes and electrocatalysts [8]. 

Abstract There have been numerous studies on modifying DuPont s Nafion (a perfluorosulfonic acid polymer) in order to improve the performance of this membrane material in a direct methanol fuel cell. Modifications focused on making Nafion a better methanol barrier, without sacrificing proton conductivity, so that methanol crossover during fuel cell operation is minimized. In this chapter, a brief literature survey of such modifications is presented, along with recent experimental results (membrane properties and fuel cell performance curves) for (1) thick Nafion films, (2) Nafion blended with Teflon-FEP or Teflon-PFA, and (3) Nafion doped with polybenzimidazole. 

A number of companies have produced commercial perfluorosulfonic acid membranes, with trade names including Nafion, Flemion, Aciplex, Aquivion, and Fumion [8]. However, since methanol readily transports across these membranes, the efficiency of DMFCs operating with these membranes is rather low, as the methanol reacts at the cathode to produce carbon dioxide and water (reducing the coulombic efficiency of the cell). It is, therefore, important to modify the properties of these membranes to suppress as much as possible the methanol crossover. 

This chapter reviews characteristics and performance of modified sulfonic acid-based membranes, particularly composite membranes including inorganic fillers and short-side chain perfluorosulfonic membranes for intermediate temperature applications. The characteristics of these systems for operation in direct alcohol fuel cells, in polymer membrane (PEM) electrolyser and automotive PEM fuel cells are analyzed. 

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