Corrosion-resistant and conductive Ti–Nb–O coatings tailored for ultra-low Pt-loaded BPPs and PTLs in PEM electrolyzers

We develop highly corrosion-resistant and conductive Ti–Nb–O coatings for metallic components — bipolar plates (BPPs) and porous transport layers (PTLs) — in PEM water electrolyzers. Using reactive high-power impulse magnetron sputtering (HiPIMS), we deposit compact 200 nm bilayer coatings onto SS316L substrates, systematically tailoring their composition. By precisely controlling oxygen partial pressure and Nb/Ti ratio, we adjust stoichiometry and structure, directly affecting electrical resistivity and corrosion resistance. We examine interfacial contact resistance (ICR) and electrochemical parameters before and after accelerated corrosion testing. Optimized coatings exhibit resistivity on the order of 1 0 − 4 Ω ⋅ cm and extremely low corrosion current densities ( J corr = 0 . 01 – 0 . 08 μ A / cm 2 ), well below the U.S. DOE 2026 target. Most importantly, these coatings enable the ICR target after accelerated corrosion testing with a Pt overlayer as thin as 5 nm, reducing Pt loading by up to two orders of magnitude compared to conventional approaches. • 200 nm Ti–Nb–O bilayer coatings for BPPs and PTLs made by HiPIMS. • Tailored composition and structure yield compact, conductive coatings. • DOE ICR target met after accelerated corrosion test with 5 nm Pt overlayer. • Pt loading reduced by up to two orders of magnitude versus conventional coatings. • Coatings enable durable PEM electrolyzers with less reliance on precious metals.