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

TL;DR

This paper presents the development of corrosion-resistant, conductive Ti-Nb-O coatings for PEM electrolyzer components, enabling ultra-low platinum loading while maintaining performance and durability.

Contribution

It introduces a novel reactive HiPIMS process to tailor Ti-Nb-O coatings with optimized composition for enhanced corrosion resistance and electrical conductivity in PEM electrolyzers.

Findings

Coatings achieve resistivity around 10^-4 Ohmcm.

Extremely low corrosion current densities (J_corr = 0.01-0.08 uA/cm^2).

Pt loading reduced by up to two orders of magnitude.

Abstract

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 10^-4 Ohmcm and extremely low corrosion current densities (J_corr = 0.01-0.08 uA/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.