Titanium-Based Binary (TiN/316L) and Ternary Nitride (TiAL(x:y)N/316L) Coatings Systems for Proton Exchange Membrane Fuel Cell Metallic Bipolar Plates

The sustainable development of the world requires a cheap and sustainable source of continuous energy supply. Hydrogen fuel cells can be an effective solution, with proton exchange membrane fuel cells as a potential candidate for portable devices and electric vehicles. The bipolar plate is a critical component of proton exchange membrane fuel cells, with a large proportion of cost and weight associated with it. Binary and ternary metal nitride coatings can be applied on 316L for bipolar plate application to achieve better corrosion resistance, protection efficiency, interfacial characteristics, high power density and low-cost manufacturability. In this research work, alloy target-based novel ternary metal nitride coatings, i.e., TiAl(80:20)N, TiAl(70:30)N and TiAl(50:50)N, on 316 L substrate and a binary metal nitride coating, i.e., TiN, on 316L substrate are compared with bare 316L for bipolar plate material. Cathodic arc physical vapor deposition is used for the coating process, and the applied coatings are characterized by XRD, SEM and EDAX. The hydrophobic nature for coating water management ability is evaluated using a water droplet test. Open-circuit potential, potentiodynamic testing and electrochemical impedance spectroscopy are used for electrochemical corrosion characterization of the applied coatings. The maximum open-circuit potential is obtained for TiAl(80:20)N-coated 316L, which is ~27.4% higher than the second-highest TiAl(70:30)N-coated 316L. However, the Tafel extrapolation method indicates that the protection efficiency of TiAl(70:30)N-coated 316L is 15.76% higher compared to TiAl(80:20)N-coated 316L. For the application of bipolar plates, the ternary metal nitride coatings demonstrated superior performance under the tested conditions compared to both the binary metal nitride coating and bare 316L stainless steel.