Stainless Steel Activation for Efficient Alkaline Oxygen Evolution in Advanced Electrolyzers

Abstract Designing robust and cost‐effective electrocatalysts for efficient alkaline oxygen evolution reaction (OER) is of great significance in the field of water electrolysis. In this study, we introduce an electrochemical strategy to activate stainless steel (SS) electrodes for efficient OER. By cycling the SS electrode within a potential window that encompasses the Fe(II)↔Fe(III) process, we can greatly enhance its OER activity compared to using a potential window that excludes this redox reaction, decreasing the overpotential at current density of 100 mA cm −2 by 40 mV. Electrochemical characterization, Inductively Coupled Plasma – Optical Emission Spectroscopy and operando Raman measurements demonstrated that the Fe leaching at the SS surface can be accelerated through a Fe → γ‐Fe 2 O 3 → Fe 3 O 4 or FeO → Fe 2+ (aq.) conversion process, leading to the sustained exposure of Cr and Ni species. While Cr leaching occurs during its oxidation process, Ni species display higher resistance to leaching and gradually accumulate on the SS surface in the form of OER‐active Fe‐incorporated NiOOH species. Furthermore, a potential‐pulse strategy was also introduced to regenerate the OER‐activity of 316‐type SS for stable OER, both in the three‐electrode configuration (without performance decay after 300 h at 350 mA cm −2 ) and in an alkaline water electrolyzer (ca. 30 mV cell voltage increase after accelerated stress test‐AST). The AST‐stabilized cell can still reach 1000 mA cm −2 and 4000 mA cm −2 at cell voltages of 1.69 V and 2.1 V, which makes it competitive with state‐of‐the‐art electrolyzers based on ion‐exchange‐membranes using Ir‐based anodes. This article is protected by copyright. All rights reserved