Carbon Bipolar Plates in PEM Water Electrolysis: Bust or Must?

Abstract Reducing the cost of PEM water electrolyzers is crucial for making green hydrogen economically viable achievable by cheaper catalysts as well as bipolar plates. This study demonstrates for the first time the use of uncoated carbon bipolar plates (C‐BPs) as an alternative to titanium bipolar plates (Ti‐BPs). The corrosion phenomena of C‐BPs versus Ti‐BPs are investigated through ex situ and in situ accelerated stress tests. The findings show that pH values, especially between 1 and 0, exponentially influence the corrosion current density of bipolar plates. Ex situ tests revealed significantly higher corrosion current densities for C‐BPs compared to Ti‐BPs (e.g., 170 times higher at pH 1 and 80 °C). Yet, tests applying C‐BPs in a Proton Exchange Membrane Electrolyzer operated for at least 567 h at alternating current densities of 1 and 3 A cm⁻ 2 with low degradation rates (16.41 µV h⁻¹ at 1 A cm⁻ 2 and 31.92 µV h⁻¹ at 3 A cm⁻ 2 ), comparable to Ti‐BPs. Contrary to general perceptions, C‐BPs are stable under application‐ready conditions and do not corrode as previously expected. This study highlights the potential of C‐BPs in electrolyzers, showcasing the potential to reduce the costs of the electrolyzers.