Long-term operation of Nb-coated stainless steel bipolar plates for proton exchange membrane water electrolyzers

Proton exchange membrane water electrolysis (PEMWE) is the most promising technology for green hydrogen production using renewable electricity, but it is expensive due to the Ti bipolar plates (BPPs). Herein, a PEMWE stack with coated stainless steel (ss) BPPs (Nb/Ti/ss-BPP and Nb/ss-BPP) is reported, which operates for about 14 000 h at 1.63 ± 0.12 A cm${}^{-2}$ and 65 °C. The average degradation rate is as low as 1.2% or 5.5 µV h${}^{-1}$. Scanning electrode microcopy reveals no signs of corrosion of the ss beneath the coatings. The interfacial contact resistance increases due to the formation of poorly conductive amorphous Nb oxides, as shown by atomic force microscopy and X-Ray photoelectron spectroscopy, although it does not affect the cell performance. The results prove that Ti is not needed anymore as base material for manufacturing the BPPs, thus the cost of PEMWE can be significantly reduced. (© 2022 The Authors. Advanced Energy and Sustainability Research published by Wiley‐VCH GmbH)