Preparation of Ta-based layer on SS316N as bipolar plate of high temperature proton exchange membrane fuel cells by molten salts disproportionation reaction

In this study, a dense Ta-based layer with a thickness of 400 nm was fabricated on SS316N bipolar plates (Ta-SS316N) by using a disproportionation reaction of Ta in a K 2 TaF 7 -Ta(powders)-KCl-NaCl molten salt system at 900 °C for 6 h. According to XRD analysis , the Ta-based layer was mainly composed of metallic Ta as well as Ta 2 N 0.86 . In the simulated HT-PEMFC cathode environment, the corrosion current density of Ta-SS316N obtained from the potentiodynamicl polarization curves was 0.96 μA/cm 2 , which meets the 2025 U S. DOE standard. Compared to the SS316N substrate, Ta-SS316N showed two orders of magnitude higher corrosion resistance and nearly 1 V higher self-corrosion potential, with an interfacial contact resistance of 27.5 mΩ∙cm 2 , accounting for about one-quarter that of SS316N substrate. This provides a low-cost, easy-to-operate method to prepare Ta-based layer on stainless steel bipolar plates used for HT-PEMFC.