An effective alkaline solid electrolyte with magnetic field-aligned Fe3O4–GO nanofillers in a polybenzimidazole membrane for methanol fuel cells

In this work, alkaline-doped polybenzimidazole/magnetite–graphene oxide (PBI/Fe3O4–GO) nanocomposite membranes are successfully synthesized for enhanced ion conduction and suppressed alcohol permeation for use in direct methanol alkaline fuel cells (DMAFCs). The structural, morphological, and magnetic properties of Fe3O4–GO nanofillers are thoroughly investigated. During the membrane drying step, the Fe3O4–GO nanofillers are aligned in a polymeric PBI matrix using an applied magnetic field (MF). Without an MF, the nanofillers are randomly distributed in the PBI matrix. The composite membrane with the MF demonstrates a 2- to 3-fold increase in hydroxide conductivity (7.6 × 10−2 S cm−1) and a one-order of magnitude reduction in fuel permeability (9.96×10−7 cm2 s−1) compared to the other samples. The potassium hydroxide (KOH)-doped PBI/Fe3O4–GO composite with MF achieves a higher maximum power density (Pmax) of 226 mW cm−2 at 80 °C than the other samples. The composite membrane with an MF demonstrates good long-term durability of 107 h with low voltage decay (6.5 × 10−4 V h−1) at high alkaline concentrations (6 M KOH). The results indicate that a small amount (0.5 wt%) of Fe3O4–GO nanofillers has an extensive effect on membrane properties in DMAFCs. [Display omitted] •PBI/Fe3O4–GO composite electrolyte for direct alkaline methanol fuel cells.•Fe3O4–GO nanofillers are aligned in PBI matrix using magnetic field.•Three-fold increase in conductivity and one-order magnitude suppress in permeability.•PBI/Fe3O4–GO membrane with MF exhibits a Pmax value of 226 mW cm−2 at 80 °C.•PBI/Fe3O4–GO membrane with MF demonstrates stable long-term discharge voltage.