Synthesis and characterization of new proton‐exchange membranes based on poly‐1‐vinyl‐1,2,4‐triazole doped with phenol‐2,4‐disulfonic acid

Poly‐1‐vinyl‐1,2,4‐triazole (PVT) was synthesized in isolated yield by free radical polymerization of 1‐vinyl‐1,2,4‐triazole. The number average molecular weight and weight average molecular weight of the synthesized PVT, determined by gel permeation chromatography, was 88 567 and 153 309 Da, respectively. PVT had a unimodal molecular weight distribution with a polydispersity coefficient of 1.7. Mixing PVT with phenol‐2,4‐disulfonic acid (PDSA) in the presence of a polyvinyl alcohol cross‐linked with oxalic acid produces proton exchange membranes having different PVT:PDSA ratios. The composition and structure of the membranes were established by elemental analysis, energy‐dispersive X‐ray spectroscopy (EDS), scanning electron microscope (SEM), Fourier‐transform infrared spectroscopy (FT‐IR), and nuclear magnetic resonance spectroscopy (NMR). FT‐IR and 15N NMR studies have shown that the interaction of PVT with PDSA was accompanied by the formation of acid‐base complexes due to proton transfer from PDSA to the triazole rings of PVT. Formation of acid‐base complexes PVT‐PDSA additionally stabilizes membranes and increases their thermal stability. The SEM study showed that the membrane surface was homogeneous. The properties of membranes, such as thermal and oxidative stability, ion‐exchange capacity, proton conductivity, water uptake, and their mechanical properties, have been studied. The commercial membrane Nafion 212 was used as a comparison. The proton conductivity of membranes increases with an increase in the content of PDSA in their composition and for membranes 1‐3 was 59.80, 7.30, 6.23 mS/cm, respectively. The activation energies for proton transfer across the membranes were 19.5, 21.6, and 38.2 kJ/mol for the membranes 1‐3, respectively. Water uptake, ion‐exchange capacity, and proton conductivity depend on the content of PDSA in the membrane. The membranes obtained were tested in a test cell of an ElectroChem hydrogen fuel cell (USA) at a temperature of 25°C with the supply of humidified hydrogen and air.