Electrochemical surface modification of stainless steel type-304 as an effective electrode for water splitting application

초록

Stainless steel type-304 (SS304) is a material that contains Fe, Cr, and Ni with a weight ratio of 7:2:1, in which Fe and Ni are distinguished as efficient electrocatalytic elements for water splitting application. However, for practical use in industrial field, additional electrochemical surface modification of SS304 should be carried out not only to obtain micro-/nanostructures with large surface area for electrocatalytic reactions but also to prevent electrochemical passivation caused by Cr. In this regard, herein, we have investigated several electrochemical surface modification approaches of SS304 for improved electrocatalytic performance in water splitting application. First, electrochemical oxidation of SS304 under harsh condition affects the increasing surface composition of Ni content due to the combination of electromigration and drag force, therefore, electrocatalytic performance for HER is improved with an overpotential of 466 mV at 10 mA cm-2. Second, stainless steel-based nanoporous electrocatalysts have been prepared by anodization using non-aqueous electrolyte followed by annealing treatment in Ar/H2. The obtained electrode exhibits high electrocatalytic activity for HER with an overpotential of 370 mV after at 10 mA cm-2 due to large surface area and oxygen vacancies. Finally, trace amount of Ru-doped stainless steel-based electrocatalysts with high flexibility and durability have been obtained by single-step anodization. Due to the unique structure of electrode facilitating the mass transfer and high electron density provided by doped Ru species, the of Ru-doped stainless steel-based electrode shows an enhanced bifunctional electrocatalytic characteristics with an overpotential of 331 and 310 mV for HER and OER, respectively, at 10 mA cm-2.