High performance Nb/NbN coatings fabricated by bias-voltage-controlled magnetron sputtering for water electrolyzer bipolar plates anode anti-corrosion application

The Proton exchange membrane water electrolysis (PEMWE) represent one of the most promising strategies for green hydrogen production. As critical components of PEMWE, bipolar plates endure aggressive corrosive environments. This study developed niobium/niobium nitride (Nb/NbN) coatings on titanium substrates using pulsed direct current magnetron sputtering (PDCMS) with bias voltage optimization. The results indicate that bias voltage adjustments profoundly influence film crystallinity and microstructure. The optimized NbN coating exhibit enhanced surface smoothness, superior corrosion resistance with the low corrosion current density of 3.27 μA/cm²after 2 h potentiostatic polarization and the potentiodynamic parameters (E_corr = 0.23 V vs. RHE, i_corr = 0.204 μA/cm²), along with excellent conductivity exhibiting interfacial contact resistance (ICR) of 3.12 mΩ cm²pre-corrosion and 12.58 mΩ cm²post-corrosion. Therefore, the pulsed direct current magnetron-sputtered Nb/NbN coating is promising as a cost-effective, non-precious metal solution for the fabrication of large-scale bipolar plates.