Electrochemical durability benchmarking of unmodified 316L stainless steel electrodes for alkaline water electrolysis: 1000-h validation
摘要
Establishing durability benchmarks for unmodified electrode materials is essential for the rational design and cost optimization of alkaline water electrolyzers, yet systematic validations beyond a few hundred hours remain scarce. This study presents a comprehensive electrochemical characterization of unmodified 316L stainless steel electrodes during 1000 h of continuous galvanostatic operation at 70 °C and 50 mA cm−2 in 30 wt% KOH — the longest reported test for this electrode material. The system exhibited 2.4% voltage drift (46 mV) while maintaining 97.2 ± 1.8% Faraday efficiency. Electrochemical impedance spectroscopy tracked interfacial evolution, revealing charge transfer resistance increase from 2.77 to 3.10 Ω cm2 (12%) over the full test duration (chi-squared < 1 × 10−3). Performance characterization across 25–200 mA cm−2 demonstrated optimal specific energy consumption of 28.1 kWh Nm−3 at 100 mA cm−2. Temperature-dependent studies (25–70 °C) yielded activation energies of 28 kJ mol−1 for hydrogen evolution and 42 kJ mol−1 for oxygen evolution. Complementary gravimetric (0.0047 mm year−1) and electrochemical (0.0089 mm year−1) corrosion assessment projected operational lifetimes exceeding 200 years. X-ray photoelectron spectroscopy revealed protective chromium-rich passive layer formation with Cr/Fe ratio increasing from 0.35 to 1.10. Although the electrochemical performance of unmodified 316L stainless steel is inferior to that of catalyst-modified electrodes, these results establish essential baseline durability benchmarks against which surface-modified approaches can be meaningfully compared, and demonstrate the viability of earth-abundant, cost-effective electrode materials for long-duration alkaline electrolysis applications.
Graphical abstract