Investigation of Metal-Graphite Coatings for PEMFC Bipolar Plate Using Atmospheric Plasma Thermal Spraying

To realize the commercial application of metal bipolar plates in proton exchange membrane fuel cells (PEMFCs), it is important to develop coatings that are both durable and have low interfacial contact resistance (ICR). In this study, atmospheric plasma spraying (APS) was utilized to prepare nickel–graphite (Ni–G) and copper–graphite (Cu–G) coatings on titanium bipolar plates. This study investigates the effect of different graphite contents on the phase composition, microstructure, corrosion resistance, and electrical conductivity of the coatings. The results show that higher graphite content leads to better performance. The potentiostatic corrosion current densities of the Ni–G and Cu–G coated bipolar plates are 1.05 × 10−4 A·cm−2 and 0.91 × 10−4 A·cm−2, respectively. Similarly, the ICR values of the coated bipolar plates are 25.2 mΩ·cm−2 and 38.9 mΩ·cm−2 before and after cathodic polarization for Ni–G, and 17.4 mΩ·cm−2 and 21.2 mΩ·cm−2 for Cu–G. These results suggest that metal–graphite coatings deposited by APS represent a viable strategy for titanium bipolar plates.