Highly conductive and corrosion-resistant NbN coatings on Ti bipolar plate for proton exchange membrane water electrolysis

Proton exchange membrane water electrolysis (PEMWE) is one of the most promising strategies to produce green hydrogen energy, and it is crucial to exploit highly conductive and good corrosion-resistant coatings on bipolar plates (BPs), one of the core components in PEMWE cells. In this work, NbN coatings are deposited on Ti BPs by magnetron sputtering to improve the corrosion resistance and conductivity, for which the critical process parameters, such as the working pressure, partial nitrogen pressure and deposition temperature are well optimized. It is found that the compact microstructure, highly conductive δ-NbN and uniform nanoparticles play a dominant role in the synergistic improvement of the corrosion resistance and electrical conductivity of NbN coatings. The optimized NbN coatings exhibit excellent corrosion resistance with the low corrosion current density of 1.1 × 10⁻⁸ A cm⁻², a high potential value of -0.005 V vs. SCE and a low ICR value of 15.8 mΩ cm² @ 1.5 MPa. Accordingly, NbN coatings can be a promising candidate for the development of the low-cost and high-anti-corrosion Ti BPs of PEMWE.