Preparation and properties and performance study of chopped carbon fiber/polyvinylidene fluoride/expanded graphite composite bipolar plates utilizing surface-coated carbon nanotubes

The bipolar plate is an important part of the proton exchange membrane fuel cell, which has high requirements for mechanical properties and strength. Composite bipolar plates have the advantages of easy processing and corrosion resistance, but there are problems such as difficulty in balancing between mechanical properties and electrical conductivity. In this study, surface-coating modification of chopped carbon fibers was carried out by catalytic chemical vapor deposition, and multi-walled carbon nanotube-coated carbon fiber composites with better interfacial contact properties and improved specific surface area were prepared and added to polyvinylidene fluoride/expanded graphite to synthesize composite bipolar plates. Due to the selective distribution of carbon nanotubes and the synergistic construction of conductive pathways with carbon fibers, the performance of the composite bipolar plate was improved, with a conductivity of 116.01 S/cm, a flexural strength of 50.37 MPa, and both good hydrophobicity and corrosion resistance and a corrosion current density of 0.804 µA cm⁻². The results show that the prepared composite bipolar plates meet the requirements in fuel cell use, and the use of carbon nanotubes coated with carbon fibers to synergistically construct conductive networks has also proven to be a potential performance enhancer for composite bipolar plates.