Carbon-coated stainless steel as a bipolar plate material in PEM water electrolyzers

The kinetically sluggish oxygen evolution reaction in proton exchange membrane water electrolyzers (PEMWEs) leads to high potentials of >1.5 V vs RHE at the anode electrode during operation. In contrast, an investigation with an in situ reference electrode indicates a much lower potential at the anode side of the bipolar plate which would allow the use of stainless steel and carbon as the bipolar plate materials. This decoupling is induced by the low conductivity of the circulating deionized water. In single cell electrolyzer tests, we show that carbon-coated 316L (C-316L) stainless steel is suitable as a bipolar plate material in contact with the anode and cathode sides of the PEMWE. The coating remains stable throughout the experiments, i.e., 720 h at the anode and 1000 h at the cathode side. Based on these results we regard carbon-coated stainless steel as a sustainable solution for the large-scale application of PEM water electrolysis since it might replace (Pt-coated) titanium in the bipolar plate.