Crosslinked sulfonated poly(vinyl alcohol)/sulfonated multi-walled carbon nanotubes nanocomposite membranes for direct methanol fuel cells

► We synthesized sulfonated PVA/sulfonated MWNTs nanocomposite membranes. ► The methanol permeability of the this membranes were remarkably lower than Nafion. ► These membranes showed higher proton conductivity from 0.032 to 0.075 S/cm. Organic/inorganic membranes based on sulfonated poly(vinyl alcohol) (s-PVA) and sulfonated multi-walled carbon nanotubes (s-MWNTs) nanocomposite membranes (SPVA) with various compositions were prepared for use as proton exchange membranes in direct membrane fuel cells (DMFCs). The SPVA membranes were cross-linked with both glutaraldehyde and s-MWNTs to reduce the level of water (methanol) uptake. The unreacted carboxylic acid and sulfonic acid of the s-MWNTs were also cross-linked with the hydroxyl groups of the PVA matrix. The ion exchange capacity (IEC) and proton conductivity of the membranes initially increased with increasing amount of s-MWNTs, because the s-MWNTs have abundant sulfonic acid groups. The composite membranes exhibited excellent proton conductivity ranging from 0.032 to 0.075 S/cm as well as low methanol permeability ranging from 1.12 × 10 −8 to 3.32 × 10 −9 cm 2 s −1 at 60.