Nafion/mordenite hybrid membrane for high-temperature operation of polymer electrolyte membrane fuel cell

Nafion/mordenite hybrid membranes for the operation of polymer electrolyte membrane fuel cells (PEMFCs) above 100 °C were prepared by mixing of H⁺-form mordenite powder and perfluorosulfonylfluoride copolymer resin. PEMFC operation above 100 °C reduces CO poisoning as well as passivation of the Pt anode electrocatalyst by other condensable species. The physico-chemical properties of hybrid membranes were investigated by tensile strength and proton conductivity measurements. As the mordenite content increases at the high temperature region, the proton conductivity of hybrid membranes increased due to the late dehydration rate of existent water in the mordenite. Also, from the results of current–voltage relationship for single cells under 130 °C of operation condition, the hybrid membrane cell with 10 wt.% mordenite showed better performance than that of the others over the entire current density range. This result indicated that the existent water in the hybrid membrane containing 10 wt.% mordenite was higher than that with the others, thereby maintaining its conductivity. The Nafion/mordenite hybrid membrane prepared by this present method is thought to be a satisfactory polymer electrolyte membrane for PEMFC operation above 100 °C.     

Directly copolymerized poly(arylene sulfide sulfone) disulfonated copolymers for PEM‐based fuel cell systems. I. Synthesis and characterization

Direct aromatic nucleophilic substitution polycondensations of disodium 3,3′‐disulfonate‐4,4′‐difluorodiphenylsulfone (SDFDPS), 4,4′‐difluorodiphenylsulfone (DFDPS) (or their chlorinated analogs), and 4,4′‐thiobisbenzenethiol in the presence of potassium carbonate were investigated. Electrophilic aromatic substitution was employed to synthesize the SDFDPS comonomer in high yields and purity. High molecular weight disulfonated copolymers were easily obtained using the SDFDPS monomers, but in general, slower rates and a lower molecular weight copolymer were obtained using the analogous chlorinated monomers. Tough and ductile membranes were solution cast from N,N‐dimethylacetamide for both series of copolymers. The degrees of disulfonation (20–50%) were controlled by varying the ratio of disulfonated to unsulfonated comonomers. Precise control of the ionic concentration, well‐defined ionic locations, and enhanced stability due to the deactivated position of the –SO₃H group are some of the suggested advantages of direct copolymerization of sulfonated monomers. Further publications will discuss additional characteristics of these copolymers that have the same repeat unit, but different molecular weights, using methanol permeability, water uptake, protonic conductivity, and dynamic mechanical analysis. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2964‐2976, 2005     

Convenient One‐Pot Protocol for an Exclusive Synthesis of 4‐Cyano/ethoxycarbonyl‐2,2‐dimethyl‐2H‐chromene and/or 3‐Cyano/ethoxycarbonyl‐2‐isopropyl‐benzo[b]furan from a Single Oxo‐ylide

[{2‐(Fluoroaryloxy)‐2‐methyl‐propanoyl}‐(cyano/ethoxycarbonyl) methylene]triphenylphosphoranes underwent microwave‐assisted tandem intramolecular Wittig and Claisen rearrangement and internal cyclization reactions to afford fluoro‐substituted 2,2‐dimethyl‐2H‐chromenes and/or 2‐isopropyl‐benzo[b]furans in good yield. Upon controlled microwave irradiation in the presence of Nafion H catalyst in xylene, the oxo‐ylides selectively formed 4‐cyano/ethoxycarbonyl‐2,2‐dimethyl‐2H‐chromenes. Microwave irradiation of the same oxo‐ylide in the presence of K₂CO₃ as catalyst or in a polar solvent–like sulfolane resulted in the exclusive formation of the corresponding fluoro‐substituted 3‐cyano/ethoxycarbonyl‐2‐isopropyl‐benzo[b]furans.     

Electrocatalytic oxidation of formic acid on a glassy-carbon-Nafion-polyaniline-palladium nanoparticle electrode: Effect of the polymer matrix state

The rate of decomposition of formic acid on a glassy-carbon-Nafion-polyaniline-palladium nanoparticle composite as a function of the state and amount of polyaniline in the composite is studied.     

Electrochemical behavior of single-carbon organic compounds on a composite nafion-polyaniline-palladium particle electrode in acid solutions

Electrooxidation and adsorption of formic acid, methanol, and formaldehyde at a composite electrode and the influence of the composite formation conditions on these processes are studied.     

The effects of the potential and polarization time on the performance of ionic polymer metal composite actuators: a control of forward and reverse displacements

This paper focuses on the dependence of various waveforms of the potential on the displacement of Nafion‐platinum based IPMC actuators at 40 and 90% relative humidity (RH). In comparison with simpler square waveforms, a waveform that is being composed by inclusion of a rest potential of 0 V has given a longer displacement. This benefit was effective at lower humidity conditions. By a polarization, the actuators show three major displacement processes of maximum forward displacement, steady forward displacement, and maximum reverse displacement. Here, the dependence of the potential and polarization time on these displacements has been carefully examined. An increase in the forward displacement by the potential does not strongly affect a slower reverse relaxation. To give a suitable relaxation period before a polarity switching of the potential seems effective to release the internal stress of the actuator. An elevated drive potential has decreased in the bending speed apparently. Finally, it has been noted that the ‘recovery’ of the maximum displacement is possible if a suitable waveform is applied to the actuator. This recovery effect is more remarkable at higher dive potential. Copyright © 2007 John Wiley & Sons, Ltd.     

Electrocatalytic Oxidation of NADH Based on Self-assembled Colloidal Gold and Nafion Matrixes and Co Complex Mediator

Nicotinamide adenine dinucleotide (NAD ) and its reduced form NADH used as coenzymes by over 300 dehydrogenases have been the subjects of numerous studies. Direct oxidation of NADH at a bare electrode only proceeds at high overpotentials, which finally le…     

Pt/SiO2 as addition to multilayer SPSU/PTFE composite membrane for fuel cells

A multilayer composite membrane was prepared by reinforcing sulfonated polysulfone (SPSU) with porous polytetrafluoroethylene (PTFE), and adding Pt/SiO₂–Nafion® membranes on both sides of the SPSU/PTFE membrane to self‐humidify and protect the inside membrane. The ex situ Fenton test and open circuit voltage (OCV) accelerated test show that the composite membrane has better stability than the initial membrane because of the protection of the outside Pt/SiO₂–Nafion layers. The composite membrane has similar performance to that of NRE‐212 under the fully humidified condition and better performance than NRE‐212 without humidifying. The self‐humidifying membrane shows great potential for use in low humidifying conditions. Copyright © 2008 John Wiley & Sons, Ltd.