2000 kW Alkaline Water Electrolyzer: Stability Evaluation of Electrodes and Separators After a Seven-Year Long-Term Run

Alkaline water electrolysis (AWE) is the most mature technology for green hydrogen production, but it often suffers from performance degradation during industrial operation, which limits the electrolytic efficiency and service life. This study evaluates the long-term stability of core components in AWE–nickel foam (NF) electrodes and poly(phenylene sulfide) (PPS) separators, from a 2000 kW industrial electrolyzer operated at 220 mA cm–2 for seven years. The deposition of Iron (Fe) species on electrodes enhances their electrocatalytic activity. Compared with fresh NF, the oxygen evolution reaction (OER) overpotential is decreased by 315 mV, and the hydrogen evolution reaction (HER) overpotential is decreased by 44 mV at 100 mA cm–2. X-ray photoelectron spectroscopy (XPS) depth profiling reveals that approximately one-third of the sulfur in PPS has been oxidized to −SO– and −SO2– groups with an oxidation depth of about 7.3 μm. FexOy deposits have accumulated in the depressions of the woven-fabric PPS, especially in the mastoid-compressed regions. At 30 °C, the surface resistance of used PPS increases significantly compared to that of fresh PPS. However, as the temperature rises, the difference in surface resistance gradually diminishes to zero at 80 °C. Due to deformation and oxidation induced by uneven mechanical pressure and electrochemical erosion, the mechanical strength has decreased by approximately 50%, and the gas permeation has doubled. Overall, the catalytic activity of NF electrodes and the ion conductivity of PPS exhibit no significant degradation after seven years of industrial operation. We hope that this work provides insight into the rational design of laboratory and industrial materials and electrolyzers for AWE.