High-performance polymer-carbon composites for PEMFC bipolar plates reinforced with waste-derived synthetic graphite

Abstract Lightweight polymer–carbon composite bipolar plates for proton exchange membrane fuel cells (PEMFCs) were fabricated using synthetic graphite (SG) derived from waste coal tar pitch as the primary conductive filler, phenolic resin as the matrix, and short carbon fibres as secondary reinforcement. Compression moulding was employed to produce composites at a fixed bulk density of 1.6 g cm −3 , enabling reduced material loading while maintaining structural integrity. In SG–phenolic resin composites, an optimized composition of SG80-PR20resin established a continuous graphite network, resulting in an in-plane electrical conductivity of ~35 S cm −1 and a through-plane conductivity of ~57 S cm −1 without applied pressure. The introduction of carbon fibres produced a hybrid conductive architecture, with an optimum at ~3 wt% fibre loading, where in-plane and through-plane conductivities increased to ~54 S cm −1 and ~55 S cm −1 under compression, respectively. The same composition exhibited enhanced mechanical performance, with flexural strength of ~55–58 MPa and flexural modulus of ~13 GPa. Thermogravimetric and calorimetric analyses indicated high thermal stability of the composite system and reduced resin degradation upon fibre incorporation. Comparative evaluation with natural graphite–based composites prepared under identical conditions demonstrated the role of synthetic graphite in promoting more efficient conductive pathways and mechanically robust composite structures suitable for lightweight PEMFC bipolar plate applications.