Graciela C. Abuin

The search of novel materials for anion exchange membranes (AEMs) is a key factor in addressing challenges of electrochemical energy conversion and storage devices in terms of cost, durability, efficiency, and up‐scalability; and composite materials based in electrospun nanofibers have a great potential in this regard. We report a facile preparation method of an AEM composed by polyvinyl alcohol (PVA) nanofibers crosslinked with glutaraldehyde (GA) and reinforced with poly[2‐2′‐(m‐phenylene)‐5‐5′‐bibenzimidazole] (ABPBI) polymer, characterizing it as an AEM in a liquid alkaline water electrolyzer (LAWE) device. Homogeneous and flexible membranes were obtained, with a good chemical stability in the doping solution (15 wt.% KOH), and better swelling resistance than pure ABPBI membranes. The membranes also showed a specific ionic conductivity of 36 mS·cm⁻¹ at 60°C and 41 mS·cm⁻¹ at 80°C, with an activation energy value of 3.5 kJ·mol⁻¹. Regarding LAWE performances, it attained current densities of 236 and 271 mA·cm⁻² for a 2 V cell voltage when operated at 50°C and 70°C, respectively. During chronopotentiometric test, neither potential drop nor change in material integrity were observed. These results provide a facile and scalable method for low cost AEMs preparation, contributing as an alternative material for its use in electrolyzers.

Crosslinked membranes have been synthesized by a casting process using polybenzimidazole (PBI) and poly(vinyl benzyl chloride) (PVBC). The membranes were quaternized with 1,4-diazabicyclo[2.2.2]octane (DABCO) to obtain fixed positive quaternary ammonium groups. XPS analysis has showed insights into the changes from crosslinked to quaternized membranes, demonstrating that the crosslinking reaction and the incorporation of DABCO have occurred, while the ¹³C-NMR corroborates the reaction of DABCO with PVBC only by one nitrogen atom. Mechanical properties were evaluated, obtaining maximum stress values around 72 MPa and 40 MPa for crosslinked and quaternized membranes, respectively. Resistance to oxidative media was also satisfactory and the membranes were evaluated in single direct ethanol fuel cell. PBI-c-PVBC/OH 1:2 membrane obtained 66 mW cm⁻² peak power density, 25% higher than commercial PBI membranes, using 0.5 bar backpressure of pure O₂ in the cathode and 1 mL min⁻¹ KOH 2M EtOH 2 M aqueous solution in the anode. When the pressure was increased, the best performance was obtained by the same membrane, reaching 70 mW cm⁻² peak power density at 2 bar O₂ backpressure. Based on the characterization and single cell performance, PBI-c-PVBC/OH membranes are considered promising candidates as anion exchange electrolytes for direct ethanol fuel cells.