Graphene-Dominated Hybrid Coatings with Highly Compacted Structure on Stainless Steel Bipolar Plates

Highly conductive corrosion protection coatings are necessary for metallic bipolar plates (BPs) of the proton-exchange membrane fuel cell. Graphene coatings have the potential of protecting metal substrates from corrosion without obscuring their excellent electrical conductivity. The electron transfer in the coatings facilitates the formation of galvanic cells, so the challenge is to block the mass transfer of the corrosion process. Here, we constructed highly compacted hybrid coatings with aligned water-dispersible graphene layers. The water-dispersible graphene (SG) held an electrical conductivity of >270 S cm^-1 while providing an unprecedented dispersibility, which can be redispersed from filter cake with a concentration of 120 mg mL^-1 or even dry state. The cohesion of the hybrid coatings was attributed to the interaction between highly aligned SG layers and the heterointerface between SG and polydopamine (PDA), as proven by the molecular dynamics simulations. The hybrid coatings presented a corrosion current density of 0.023 μA cm^-2 and an interfacial contact resistance of 9.94 mΩ cm², which meets the requirements of corrosion protection and electron transfer for the coatings on metallic BPs. The water-based fabrication method of the graphene-dominated hybrid coatings was a promising alternative of the vacuum-based deposition method for industrial production.