In this report, the electrical performance at T > 100 degrees C and low relative humidity of proton-conducting Nafion-based membranes was improved by preparing new materials based on Nafion 117 (N117) neutralized with triethylammonium (TEA(+)) and doped with the ionic liquid (IL) trifluoromethanesulfonate of triethylammonium (TEA-TF). In particular, a new two-step protocol for the preparation of [N117(x-)(TEA(+))(x)/(TEA-TF)(y)] is proposed. [N117(x-)(TEA(+))(x)/(TEA-TF)(y)] membrane is composed of ca. 30 wt % of TEA-TF. The structure of the different nanophases composing the materials and their interactions were investigated by FT-IR ATR and micro-Raman spectroscopy. The thermal stability, water uptake, and mechanical properties of the membranes were studied by thermogravimetric analysis and dynamic mechanical analysis measurements. With respect to pristine N117, the thermal and mechanical properties of the proposed materials were improved. The electric response of [N117(x-)(TEA(+))(x)/(TEA-TF)(y)] was studied by broad band dielectric spectroscopy in the frequency range from 10(-2) Hz to 10 MHz and for temperatures between 5 and 155 degrees C. In comparison to the N117 reference, the following was observed: (a) the stability range of conductivity (SRC) of the [N117(x-)(TEA(+))(x)] membrane increases up to 155 degrees C, while its sigma(DC) at T = 100 degrees C is lowered by ca. 2 orders of magnitude; (b) the SRC of [N117(x-)(TEA(+))(x)/(TEA-TF)(y)] is similar to that of [N117(x-)(TEA(+))(x)], while the sigma(DC) at 145 degrees C decreases in the order 7.3 x 10(-3) > 6.1 x 10(-3) > 9.7 x 10(-4) S x cm(-1) for [N117(x-)(TEA(+))(x)/(TEA-TF)(y)], N117, and [N117(x-)(TEA(+))(x)] membranes, respectively. In conclusion, the lower water uptake, the improved thermal and mechanical stability, and the good conductivity make [N117(x-)(TEA(+))(x)/(TEA-TF)(y)] a promising membrane to improve for application in proton exchange membrane fuel cells operating under anhydrous conditions at T > 100 degrees C.

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.

We report the design of a H2/O2 (fuel) cell for in situ μ‐Raman spectroscopic measurements. The horizontal orientation of the cell is conceived to allow the penetration of the laser beam along the z‐axis from one electrode to the other. We show that during in‐depth analyses the Raman signal is not significantly lost and the axial resolution is sufficiently good to allow quantitative and qualitative spectral interpretation. We report “proof of principle” tests performed on Nafion membranes swelled with protic ionic liquids to demonstrate the validity of the design and the potentiality of the method. Our results confirm that this experimental setup can efficiently be used to follow structural changes and concentration gradients in the electrolyte of a fuel cell operando. In particular, we have been able to resolve both in time and in space the hydration state of the membrane as well as spatial variations for the $ {\rm SO}_3^- $ coordination shell during a compositional transient state.

International audienceIn this paper, we studied the durability of PEMFC MEAs after on-site operation in stationary conditions. Harsh anode and cathode active layer degradation was monitored for Pt, C, F elements by chemical (EDS, XPS) and physical (SEM, TEM) techniques. At the cathode, Pt corrodes into Ptz⁺ species yielding severe redistribution within the MEA. Ptz⁺ dissolution and transport is favoured by activators/ligands (F or S-containing species resulting from the MEA polymers ageing, especially at the anode), which possibly act as counter ions. The presence of Ptz⁺ ions in the membrane favours chain-cutting and induces physical cross-links which modifies its thermo-mechanical, water uptake and conductivity properties. As a result, the risk of pinhole formation is greatly increased

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