Polymer fuel cells operating above 100 °C (High Temperature Polymer Electrolyte Membrane Fuel Cells, HT-PEMFCs) have gained large interest for their application to automobiles. The HT-PEMFC devices are typically made of membranes with poly(benzimidazoles), although other polymers, such as sulphonated poly(ether ether ketones) and pyridine-based materials have been reported. In this critical review, we address the state-of-the-art of membrane fabrication and their properties. A large number of papers of uneven quality has appeared in the literature during the last few years, so this review is limited to works that are judged as significant. Emphasis is put on proton transport and the physico-chemical mechanisms of proton conductivity.

Photoamidation of electron-poor olefins has been achieved by means of a radical-induced C À H functionalization in amides. Tetrabutylammonium decatungstate was used as photocatalyst of the reaction and allowed the smooth generation of different carbon-centered radicals depending on the amide structure.

Polybenzimidazoles are promising materials to replace Nafion™ as the electrolyte in HT-PEMFCs. One of their problems is striking the proper balance between the H 3 PO 4 doping level, which controls the proton conductivity, and the long-term stability properties of the membrane. Monomer modification is a promising way to maintain high conductivity levels with reduced doping. Here, we reported a novel and facile approach to obtaining an easy modular and reproducible sulfonation degree. Some aryloxy-based polybenzimidazoles were synthesized and sulfonated with different amounts of -SO 3 H. We prepared many electrolyte membranes by doping the pristine polymers in solutions with different H 3 PO 4 concentrations. The sulfonation degree greatly affected both acid uptake and conductivity. In particular, the membranes holding more protogenic groups absorbed less acid than the monosulfonated ones.However, polysulfonation was particularly efficient in improving proton conductivity at low relative humidity and doping level. We performed MEAs tests at 150 C using H 2 and air as the reactant gases, without any external humidification. We obtained power densities higher than 320 mW cm À2 , with fuel cell performances of approximately 580 mV at 0.2 A cm À2 , independent of the number of sulfonic groups. Preliminary durability tests did not show any membrane degradation over a 190 hour period. The reported membranes are therefore suitable for use in HT-PEMFCs.

Polybenzimidazoles (PBIs) are promising materials to replace Nafion as the electrolyte in polymer electrolyte membrane fuel cells (PEMFCs). The challenge with these materials is to achieve a good compromise between the H3PO4 doping level and membrane stability. This can be obtained by a proper monomer design, which can lead to better performing membrane electrode assemblies (MEAs), in terms of durability, acid leaching, and electrode safety. Here the easy and inexpensive synthesis of hexafluoropropylidene oxyPBI (F6‐oxyPBI) and bisulfonated hexafluoropropylidene oxyPBI (F6‐oxyPBI‐2SO3H) is reported. The membranes based on F6‐oxyPBI‐2SO3H are more stable in an oxidative environment and more mechanically resistant than standard PBI and F6‐oxyPBI. Whereas the attainable doping levels are low because of fluorine‐induced hydrophobicity, polysulfonation allows high proton conductivity, and fuel cell performances better than those reported for MEAs with F6PBI‐ or PBI membranes with much higher doping levels. In the case of MEA with a F6‐oxyPBI‐2SO3H membrane, a peak power density of 360 mW cm−2 is measured. Fuel cell performances of 604 mV at 0.2 A cm−2 are maintained for 800 h without membrane degradation. Low H2 permeability is measured, which remains almost unaffected during a 1000 h life‐test.