New triazinephosphonate dopants for Nafion proton exchange membranes (PEM)

A new paradigm for energy is underway demanding decarbonized energy systems. Some of them rely on emerging electrochemical devices, crucial in hydrogen technologies, including fuel cells, CO2 and water electrolysers, whose applications and performances depend on key components such as their separators/ion-exchange membranes. The most studied and already commercialized Nafion membrane shows great chemical stability, but its water content limits its high proton conduction to a limited range of operating temperatures. Here, we report the synthesis of a new series of triazinephosphonate derivatives and their use as dopants in the preparation of new modified Nafion membranes. The triazinephosphonate derivatives were prepared by substitution of chlorine atoms in cyanuric chloride. Diverse conditions were used to obtain the trisubstituted (4-hydroxyphenyl)triazinephosphonate derivatives and the (4-aminophenyl)triazinephosphonate derivatives, but with these amino counterparts, only the disubstituted compounds were obtained. The new modified Nafion membranes were prepared by casting incorporation of the synthesized 1,3,5-triazinephosphonate (TPs) derivatives. The evaluation of the proton conduction properties of the new membranes and relative humidity (RH) conditions and at 60 °C, showed that they present higher proton conductivities than the prepared Nafion membrane and similar or better proton conductivities than commercial Nafion N115, in the same experimental conditions. The Nafion-doped membrane with compound TP2 with a 1.0 wt % loading showed the highest proton conductivity with 84 mS·cm-1.

Hollow and Solid Spheres Assembled from Functionalized Macrocycles Containing Adamantane

An adamantane-based macrocycle possessing eight hydroxyl groups (1) was synthesized, in which the macrocyclic framework comprises two disubstituted adamantane molecules bearing phenyl derivatives connected to two biphenylene spacers by oxygen atoms. Furthermore, functionalized macrocycles containing methyl (2) and methoxycarbonylmethyl (3) groups were prepared. From the X-ray crystallographic analysis, the backbone of the macrocycles in all crystals had a nearly hexagonal shape with a cavity and these macrocycles could be arranged into different tubular structures dependent on the substituents. In acetone, macrocycle (1) formed stable hollow spherical aggregates with multilayer membranes. In contrast, macrocycle (3) exhibited no production of self-assembled materials in chloroform. The addition of hexane into the solution caused the generation of solid spheres and their fused network aggregates, which were finally transformed into crystals owing to the solvent effects.