Stainless steel-derived nano-porous oxide: a cost-efficient, stable, and corrosion-resistant hydrogen evolution catalyst†

Abstract

Stainless steel (SS)-based electrocatalysts have attracted considerable attention in renewable energy research, emerging as viable replacements for precious noble metal-based catalysts owing to their cost-effectiveness and widespread availability. Further, SS's ability to function as an electrode material in alkaline water electrolyzers and its inherent corrosion resistance make it a key component of sustainable energy solutions. This study focuses on the fabrication of a self-ordered nanoporous oxide layer on SS through an anodization method, followed by an investigation into the electrocatalytic activity of the resulting films for hydrogen evolution reaction (HER) and corrosion properties. Anodization creates a highly organized nano-porous metal oxide structure featuring extensive surface areas that offer abundant active sites for electrochemical reactions via the oxide formation-dissolution mechanism. The nano-porous oxide film produced demonstrates exceptional HER activity, reaching a cathodic current density of 10 mA cm⁻² with a minimal overpotential of 343 mV (versus the reversible hydrogen electrode (RHE)) in a strong alkaline medium. Moreover, the stability of the derived nano-porous oxide film remains unaffected during 50 hours of uninterrupted electrolysis, demonstrating remarkable operational resilience. Conversely, potentiodynamic polarization measurements reveal that the resulting films exhibit superior corrosion resistance in both NaCl and KOH electrolytes compared to bare SS. This enhanced resistance is attributed to the self-ordered nano-porous structure, which fosters the construction of a more uniform film with a more robust passive layer. The straightforwardness of the procedure and the widespread availability of the initial material make this an unexpectedly effective endeavour. The research demonstrated that anodized SS can achieve both corrosion resistance and catalytic activity for the HER, making this material system a viable candidate for alkaline water electrolyzer systems.