Solvent-assisted graphite loading for highly conductive phenolic resin bipolar plates for proton exchange membrane fuel cells

A highly conductive polymer-based bipolar plate is fabricated using phenolic resin and graphite for proton exchange membrane fuel cells (PEMFCs). In order to load graphite fillers up to 90 wt% and minimize the void volume, the wetting properties of the graphite and phenolic resin are key factors for ensuring high electrical conductivity of the bipolar plates through good contact and uniform dispersion of graphite fillers. Since the surface free-energies of the phenolic resin and graphite are significantly different at 107.77 and 43.3 mJ m⁻², respectively, to give a high contact angle of 87.1°, methanol with 19.6 mJ m⁻² of surface energy is incorporated to decrease the contact angle between the matrix and graphite to 11.2°. By adjusting the surface energy of the matrix system, the conductivity of a composite containing 90 wt% of graphite reaches 379 S cm⁻¹. The air permeability of the composite containing 80 wt% of graphite is less than 5 × 10⁻⁶ cm³ cm⁻² s without open pores. The flexural modulus ranges from 6700 to 11000 MPa for graphite loads between 60 and 80 wt%, respectively.