Jacques Rozière

Recent advances in the functionalisation of polybenzimidazole and polyetherketone for fuel cell applications

Abstract This article reviews progress made over the past years in the functionalisation of polybenzimidazole and polyetherketones with a view to increasing their proton conduction properties without detriment to their thermohydrolytic and chemical stability such that corresponding membranes may be employed in hydrogen oxygen (air) or direct methanol fuel cells. The approaches include complexation of polybenzimidazole with acids, grafting of groups containing sulfonic acid moieties on to polybenzimidazole by N-substitution, and direct sulfonation of polyetherketones. A further approach concerns the incorporation of inorganic proton conducting particles in the polymer matrix, and this is developed in detail for the case of hybrid sulfonated polyetheretherketone–metal(IV) phosphate membranes.

Textural and structural properties and surface acidity characterization of mesoporous silica-zirconia molecular sieves

Homogeneous mesoporous zirconium-containing MCM-41 type silica were prepared by supramolecular templating and their textural and structural properties were studied using powder X-ray diffraction, N2 porosimetry, atomic force microscopy, EXAFS, XPS, and UV–VIS–NIR diffuse reflectance spectroscopy. Their acid properties were also studied by using IR spectroscopy and by the use of catalytic tests such as the decomposition of isopropanol and the isomerization of 1-butene. The materials prepared show a good degree of crystallinity with a regular ordering of the pores into a hexagonal arrangement and high thermal stability. The specific surface area of the prepared materials decreases as the zirconium content rises. Zirconium atoms are in coordination 7 to 8 and located at the surface of the pores such that a high proportion of the oxygen atoms bonded to zirconium corresponds to surface non-condensed oxygen atoms. Both facts are responsible for the acid properties of the solids that show weak Bronsted and medium strong Lewis acidity.

Surfactant‐Assisted Synthesis of a Mesoporous Form of Zirconium Phosphate with Acidic Properties

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Advances in the Development of Inorganic–Organic Membranes for Fuel Cell Applications

Inorganic–organic membranes are characterised by the presence of a certain amount of inorganic solid within an organic polymer that serves as the matrix component. From its origins some 15 years ago as a means of conferring proton conduction properties to an insulating polymer matrix by addition of a powdered inorganic proton conductor, the methods of preparation have developed and currently include a range of approaches that allow control over the localisation of the inorganic component preferentially in the hydrophilic or hydrophobic regions of an ionomer, and incite development of morphologies ranging from nanoparticulate to extended network forms. The presence of an inorganic phase is effective in enhancing interaction between components, in limiting dimensional change and in improving fuel cell performance under high temperature, low relative humidity conditions. These approaches have enabled the field to develop from the stage of different concepts of inorganic–organic fuel cell membranes to their implementation in fuel cell stacks. Novel approaches make use of further degrees of organisation of the organic and inorganic components, for example by use of nanoporogens or bimodal/spinodal transformations.

A study of the surface acidity of acid-treated montmorillonite clay catalysts

The surface acidity of a series of commercial Sud Chemie acid-treated montmorillonite clays (K-catalysts) has been evaluated by a wide range of complementary experimental techniques. The different methods applied allow a rather complete characterisation of the surface acidity providing a complete picture of the Lewis/Bronsted acid strength/density of the surface sites. IR data show that the Bronsted sites on these catalysts are relatively weak and provide evidence for a slight increase of the strength and the density of Bronsted sites in the order K5 < K10 K20 < K30 in full agreement with the trend in iso-butene conversion, which is a measure of the strength and/or the abundancy of Bronsted sites. The apparent contradiction of these data with those obtained from the ammonia adsorption and iso-propanol conversion experiments can be explained by the structural and chemical modification of the clays upon acid treatment.

Role of post-sulfonation thermal treatment in conducting and thermal properties of sulfuric acid sulfonated poly(benzimidazole) membranes

Post-sulfonation thermal treatment (psTT) has been suggested in U.S. patent 4,634,530 for attaching a sulfonate group to the aromatic ring of polybenzimidazoles (PBI), which were shown to improve separatory capabilities of PBI membranes (PBIm). In this article, the influence of a psTT on conducting and thermal properties of sulfonated PBI (sPBI) membrane and the stability of these properties after a severe water-washing process were investigated. The nature of the interaction between sulfuric acid and PBI was also studied. Results have shown that most of the sulfuric acid molecules are ionically bonded to the imide ring and that the thermal-treated sPBI membranes retain more acid molecules after the washing process than the nonheating ones. Thermal stability of PBIm decreases with sulfonation, but it is high enough for their application in medium-temperature fuel cells. However, the psTT does not increase significantly the proton conductivity of sPBI membranes, although it improves the stability of conducting properties after the washing process, when the amount of sPBI units is less than 25%.

Proton insertion and lithium-proton exchange in spinel lithium manganates

Abstract The protonic species formed in spinel λ-MnO 2 by proton exchange for lithium ions in Li 1+ x Mn 2− x O 4 precursors have been characterised by infrared and inelastic neutron scattering spectroscopies. Proton diffusion into the lattice appears to depend on the presence of octahedral manganese vacancies, with formation of lattice hydroxyl co-existing with water. Mechanisms of proton transfer are considered in relation to lithium-proton exchange during reinsertion of lithium into the materials, and for insertion of additional protons by chemical reduction.

Periodic large mesoporous organosilicas from lyotropic liquid crystal polymer templatesElectronic supplementary information (ESI) available: TEM image, MAS NMR and FT-IR spectra, and BJH pore size distribution for PMO materials. See http://www.rsc.org/suppdata/cc/b1/b106938c/

Periodic large mesopore organosilicas have been obtained for the first time using bridged silsesquioxane (RO)3SiCH2CH2Si(OR)3 precursors and triblock copolymers as structure-directing species in acid media.

On the doping of sulfonated polybenzimidazole with strong bases

Abstract Grafting of (4-bromomethyl)benzenesulfonate onto polybenzimidazole (PBI) leads to a proton exchange polymer of variable degree of sulfonation. At high degrees of sulfonation, the membranes display a phenomenon of dehydration and contraction, which is shown to be due to the presence of a chain cross-linking strong hydrogen bond network. Immersion of proton form benzylsulfonate-grafted membranes in aqueous organic or inorganic base is sufficient to disrupt this network, and lead to rehydration and return to a swollen and flexible state, and base-doped N -benzylsulfonate-grafted PBI (PBI–BzSH) have a conductivity of 2×10 −2 S cm −1 at 25°C and 100% relative humidity. Exchange of sodium form N -benzylsulfonate-grafted PBI with H + takes place with three points of neutralisation, and in the pH range 5.5–12.4, this polymer exists predominantly in a zwitterionic form.

Mesoporous Nanostructured Nb-Doped Titanium Dioxide Microsphere Catalyst Supports for PEM Fuel Cell Electrodes

Crystalline microspheres of Nb-doped TiO(2) with a high specific surface area were synthesized using a templating method exploiting ionic interactions between nascent inorganic components and an ionomer template. The microspheres exhibit a porosity gradient, with a meso-macroporous kernel, and a mesoporous shell. The material has been investigated as cathode electrocatalyst support for polymer electrolyte membrane (PEM) fuel cells. A uniform dispersion of Pt particles on the Nb-doped TiO(2) support was obtained using a microwave method, and the electrochemical properties assessed by cyclic voltammetry. Nb-TiO(2) supported Pt demonstrated very high stability, as after 1000 voltammetric cycles, 85% of the electroactive Pt area remained compared to 47% in the case of commercial Pt on carbon. For the oxygen reduction reaction (ORR), which takes place at the cathode, the highest stability was again obtained with the Nb-doped titania-based material even though the mass activity calculated at 0.9 V vs RHE was slightly lower. The microspherical structured and mesoporous Nb-doped TiO(2) is an alternative support to carbon for PEM fuel cells.