Enhancing the performance of aluminum bipolar plates with grain-refined Ni-graphene composite coatings

The application of aluminum (Al) alloy bipolar plates (BPPs) in proton exchange membrane fuel cells (PEMFCs) is hindered by their insufficient corrosion resistance and high interfacial contact resistance (ICR) in harsh acidic environments. To address these challenges, this study developed nickel-graphene nanosheet (Ni-GNS) composite coatings on 6061 aluminum alloy via a facile electrodeposition technique. The microstructure, corrosion behavior, and interfacial conductivity of the composite coatings with varying GNS concentrations (0, 0.01, 0.05, and 0.1 g L -1 ) were systematically investigated. The results confirmed the successful incorporation of GNS, which refined the grain structure and reduced the porosity of composite coating. Electrochemical tests in a simulated PEMFC solution (pH=3 H 2 SO 4 + 0.1 ppm F - , 80°C) demonstrated that the Ni-GNS composite coatings significantly enhanced corrosion resistance compared to a pure Ni coating. The composite coating with 0.05 g L -1 GNS exhibited optimal performance, showing the lowest corrosion current density (1.16 × 10 -6 A cm -2 ) and the largest charge transfer resistance (1.18 × 10 4 Ω cm 2 ). Furthermore, all composite coatings met the DOE 2025 target for ICR (< 10 mΩ cm 2 ), with the composite coating achieving the lowest value of 4.17 mΩ cm 2 . This work demonstrates that Ni-GNS composite coatings are a promising strategy to improve both the interfacial conductivity and corrosion protection of Al-based BPPs.