Activation of low-cost stainless-steel electrodes for efficient and stable anion-exchange membrane water electrolysis

Abstract

Commercial stainless steel is gaining interest as a promising, low-cost electrode material for green hydrogen production through water electrolysis in an alkaline environment. Herein, the electrocatalytic performance of 304-type stainless steel mesh in anion-exchange membrane (AEM) cells was enhanced through a simple two-step activation process, i.e., chemical etching followed by electrochemical activation. The modified electrodes exhibited comparable hydrogen and oxygen evolution reaction properties to noble metal-based electrodes, requiring >300 mV lower cell voltage than the unmodified stainless steel-based cells to sustain a constant current of 5.0 A (1.0 A cm⁻²). Electrochemical impedance spectroscopy studies and investigation of wettability and bubble dynamics demonstrated a significant decrease in interfacial contact, charge transfer, and mass transport resistances. Characterization by X-ray photoelectron spectroscopy and transmission electron microscopy of the modified stainless-steel surface revealed the presence of nanocrystalline Fe–NiCr LDH and Ni(OH)₂/Fe(OH)₂ species when used in hydrogen and oxygen evolution sides, respectively, which may explain the significantly higher performance. Moreover, the long-term durability of the modified electrodes was assessed in a continuous flow electrolyzer where exceptional stability was observed at a constant current of 5.0 A (1.0 A cm⁻²) for 250 h. Due to its simplicity and cost-effectiveness, the proposed modification of stainless-steel electrodes has the potential for upscaling and deployment in the next-generation, low-cost AEM systems.