Chemical Leaching of Inactive Cr and Subsequent Electrochemical Resurfacing of Catalytically Active Sites in Stainless Steel for High-Rate Alkaline Hydrogen Evolution Reaction

In this study, we show a simple two-step surface engineering method that uses chemical oxidation (using KOH and NaClO in 1:2 M ratio)-assisted leaching of metals (Cr, Mn, and Ni) from the surface and an electrochemical potentiostatic activation enabled resurfacing of only catalytically active Ni and Mn of the alloy. Such surface-engineered stainless steel 304 (SS-304-Ox-ECA) foils rich in Ni(OH)2 and multivalent Mn oxides were found to have a coarse texture with uniform nanostructures. As a result of leached Cr, resurfaced catalytically active sites improved roughness with nanotexturing and enhanced the charge-transfer ability. The SS-304-Ox-ECA foil has become a high-performance HER electrocatalyst that delivered 400 mA cm-2 higher current density at -0.8 V versus RHE and demanded 210 mV lower overpotential for a current density of 100 mA cm-2 than pristine SS-304 foils in 1.0 M KOH. A smaller Tafel slope (90 mV dec-1) and a higher double-layer capacitance (2Cdl = 0.784 μF cm-2) further justified that the activity enhancement is also due to the improved HER kinetics and increased electrochemical surface area. This catalytic electrode of high abundance and low cost is a promising candidate for cost-efficient hydrogen production from water.