Mechanochemically Synthesized Transition Metal Carbide Fillers for Coating Metallic Bipolar Plates in Proton Exchange Membrane Fuel Cells

Metal bipolar plates, especially stainless steel 316 L bipolar plates, are of commercial interest due to their mechanical stability and low manufacturing cost, but they require a protective coating on their surface to improve their electrical conductivity as well as their corrosion performance. Herein, transition metal carbides (TiC, Cr 3 C 2 , NbC, VC, Mo 2 C, and TaC) are synthesized by a mechanochemical synthesis route, incorporated as electrically conductive fillers into a polyurethane‐based binder matrix, and are applied to stainless steel plates by the wet paint technique. For comparison, a commercially available graphite, the standard filler for coated metal bipolar plates, and a commercially available Cr 3 C 2 are used as fillers in coatings. All protective films show good adhesion to the metal substrate and a homogeneous filler‐binder distribution. Contact resistance measurements indicate that, among all the coatings, those with mechanochemically synthesized Cr 3 C 2 and Mo 2 C have the best conductivity performance, well below 10 mOhm cm 2 . From potentiodynamic and potentiostatic polarization tests, the Cr 3 C 2 ‐ containing coating has superior corrosion behavior, while the Mo 2 C coating is unable to protect the metal from corrosion. Based on these results, Cr 3 C 2 ‐coated stainless steel is an attractive candidate for bipolar plates in proton exchange membrane fuel cells.