International audienceThis paper deals with the performance of anhydrous proton-conducting polymers obtained by blending modified Nafion® membranes with proton conducting ionic liquids (PILs). It has been shown that the conductivities depend more on the PIL uptake than on its intrinsic conductivity. Conductivities at 130°C approaching those of current Nafion membranes at 80°C and 98% relative humidity were obtained with the best blends. These data allow considering MEA operating at 120-130°C based on membrane and electrodes incorporating these blends. This is clearly a positive feature for an implementation in hybrid vehicles powered by proton exchange membrane fuel cells (PEMFCs) operating above 100°C. Lastly, preliminary results for a PIL based on a half-neutralized diamine show an improvement in oxidation and, provided that the neutralization is optimized, a neat reinforcement of the Nafion membrane can be expected
The paper deals with proton‐conducting ionic liquids (PCILs) for use, in combination with functional polymers, in membranes operating in high temperature PEMFC. Monoammoniums derived from monoamines and half‐neutralised diamines were investigated in the form of triflates. Promising results were obtained with the half‐neutralised diamine‐based PCIL, its conduction being governed by both Grotthuss‐like and vehicular mechanisms, the respective contributions of which depend on temperature. In addition, their blending with Nafion results in a distinct reinforcement of the membrane.
A new composite proton-conducting material based on the association of an ionic liquid and a porous polymer support was prepared with the aim of applying it as an electrolyte in a proton exchange membrane fuel cell (PEMFC) at elevated temperature (130 °C). The porous support was made from a high glass-transition temperature polymer (Tg) by using the vapor-induced phase separation (VIPS) method in conditions leading to highly interconnected porous films. The ionic liquid tested was obtained by the reaction of a sulfonic acid with a tertiary amine and presents enough high-temperature stability to be used at elevated temperatures. Composite samples were prepared by immersing pieces of porous film in the ionic liquids under test. The porous support was characterized by scanning electron microscopy (SEM), gas permeation, and thermogravimetric analysis (TGA) tests, and the composite samples were characterized by mechanical and proton-conduction measurements. At 130 °C, this new material exhibits proton conductivity (20 mS cm −1 ) below, but very close to, that of the pure ionic liquid (31 mS cm −1 ) and presents, up to at least 150 °C, a storage modulus exceeding 200 MPa. This is very promising considering the PEMFC applications.
An accurate method has been developed to measure, in a single analytical run, δ 34 S in sulfite, sulfate and thio-sulfate in water samples by liquid chromatography combined with multicollector inductively coupled plasma mass spec-trometry (MC-ICPMS). The method is based on the anionic exchange separation of sulfur species prior to their online isotope ratio determination by MC-ICPMS. Mass bias correction was accomplished by a novel approach based on the addition of an internal sulfur-containing standard to the sample. This innovative approach was compared to the sample-standard bracketing procedure. On-column isotopic fractionation was observed and therefore corrected by external calibration. Isotopic ratios were calculated by linear regression slope (LRS), an advantageous method for transient signals, leading to a combined uncertainty of δ 34 S below 0.25‰ and a reproducibility below 0.5‰ for the injection of 1 µg of S. The method was successfully applied to the measurement of δ 34 S in synthetic solutions and environmental water samples. Matrix effects leading to δ 34 S overestimation were observed for sulfate in some samples with high sodium/sulfate mass ratios. The developed analytical procedure simplifies the δ 34 S analysis of liquid environmental samples since preparation steps are no longer required and allows the analysis of several sulfur-containing species in a single run.
The paper deals with the synthesis and characterisation of proton conducting ionic liquids (PCIL) and their polymer electrolytes obtained by blending modified Nafion membranes with different concentrations of PCIL. We studied the impact of the acid nature on the PCILs thermal and electrochemical performances. It has been shown that the membranes conductivities depend more on the PCIL structure than on its intrinsic conductivity. Conductivities approaching at 130°C those of current Nafion membranes at 80°C and 98% relative humidity were obtained with the best blends.
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