Proton transport for fuel cells

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A Comprehensive Study of an Acid-Based Reversible H2-Br2 Fuel Cell System

The regenerative H2-Br2 fuel cell has been a subject of notable interest and is considered as one of the suitable candidates for large scale electrical energy storage. In this study, the preliminary performance of a H2-Br2 fuel cell using both conventional as well as novel materials (Nafion and electrospun composite membranes along with Pt and RhxSy electrocatalysts) is discussed. The performance of the H2-Br2 fuel cell obtained with a conventional Nafion membrane and Pt electrocatalyst was enhanced upon employing a double-layer Br2 electrode while raising the cell temperature to 45°C. The active area and wetting characteristics of Br2 electrodes were improved upon by either pre-treating with HBr or boiling them in de-ionized water. On the other hand, similar or better performances were obtained using dual fiber electrospun composite membranes (PFSA/PPSU) versus using Nafion membranes. The RhxSy electrocatalyst proved to be more stable in the presence of HBr/Br2 than pure Pt. However, the H2 oxidation activity on RhxSy is quite low compared to that of Pt. In conclusion, a stable H2 electrocatalyst that can match the hydrogen oxidation activity obtained with Pt and a membrane with low Br2/Br− permeability are essential to prolong the lifetime of a H2-Br2 fuel cell

Insight into the multiscale structure of pre-stretched recast Nafion (R) membranes: Focus on the crystallinity features

International audienceThe structure of solution cast Nafion (R) membranes that were uniaxially stretched, and then thermally annealed was studied over an extended observation window, from a few angstroms to several hundreds of angstroms, using both Small-Angle X-Ray Scattering (SAXS) and Wide-Angle X-Ray Diffraction (WAXD). This Nafion (R) membrane preparation allowed highlighting new structural features, never reported previously. Indeed, while SAXS data evidenced moderate effect of stretching with different behaviors of the matrix and ionomer peaks, WAXD spectra showed a strong stretching induced anisotropy of the crystalline phase. These results defy the Nafion (R) structural models and call for further theoretical and experimental developments taking into account these new data. (C) 2015 Elsevier Ltd. All rights reserved