Supramolecular complexation of metal oxide clusters in PVDF-PVP blends for large scale fabrication of proton exchange membranes for fuel cells

Abstract

The perfluorosulfonic acid (PFSA) polymers have achieved great success as proton exchange membranes (PEMs) in various energy storage and conversion devices; nevertheless, the improvements regarding PEMs' synthetic cost, mechanical properties, stability and processability are still urgently required. Herein, 1 nm super acidic metal oxide cluster, H3PW12O40 (PW12), is complexed with the blends of polyvinylpyrrolidone (PVP) and polyvinylidene fluoride (PVDF) to afford nanocomposite PEMs that enables the stable and effective operation of hydrogen fuel cell devices. As the polymer matrix, the PVDF is blended with PVP via inter-chain hydrogen bonding to provide mechanical support for the nanocomposite PEMs. The further introduced PW12 clusters can interact strongly with PVP via electrostatic attraction to enhance the PEMs' mechanical strength (E = 231 MPa) and prevent the leaching of PW12 for long-term stability. Meanwhile, the incorporation of the super acidic PW12 can facilitate the fast proton transportation and therefore, lead to the significant increasement of proton conductivity to 9.8 × 10−3 S cm−1 at 70 °C and 100% RH. Due to the excellent mechanical properties and the supramolecular interaction among the components, the PEMs’ thickness can be controlled to be challenging ∼10μm for feasible large-scale continuous processing. Finally, the molecular design enables the successful fabrication of the nanocomposite PEMs into fuel cell devices with the power density as 342.8 mW cm−2. The studies not only shed light on the structure-properties of polymer nanocomposites, but also pave avenues to the design of robust composite PEMs for fuel cell appliacations.