Promoting Proton Conductivity and Methanol-Resistance of PVdF-Based PEM Membrane by Incorporating Dispersive CNT Dotted With α-Zr(HPO4)2∙H2O

Abstract

To optimize the proton transport performance of polyvinylidene fluoride (PVdF), a proton exchange membrane (PEM) material, carbon nanotube (CNT), and zirconium hydrogen phosphate (ZrP) have been blended into the PVdF matrix. Adopting a hydrothermal synthesis route, the acidic ZrP can be better conjugated with the positively charged CNT functionalized by cetyltrimethylammonium bromide (CTAB). As visualized using electroscopes, ZrP nanocrystallines are intimately dotted and homogeneously distributed on CNT. The ZrP–PVdF interaction can be attributed to hydrogen bonding between hydroxyl and F-terminal groups. By incorporating well CNT/ZrP into PVdF via solution casting, the pore architecture can be regulated; namely, the macro-voids in PVdF are greatly reduced. The composite membranes exhibit tensile stress of 48–52 MPa while sustaining the thermal stability of PVdF. The incorporated CNT/ZrP can suppress void porosity and enhance film hydrophilicity. With improved wettability, the methanol permeability can be reduced to less than 2 × 10⁻⁹ cm²∙s⁻¹, ca. one-sixth that of pure PVdF. The proton conductivity for PVdF-CNT_0.03-ZrP_0.06, with CNT and ZrP mass content respectively 3 and 6 wt% that of PVdF, attains 0.089 S·cm⁻¹ at 100°C, showing upgraded conducting capability. The membrane selectivity can be remarkably enhanced, verifying that CNT/ZrP blending is a facile and profitable approach for PEM optimization.