Rapid Room-Temperature Sulfidation of Commercial FeNiCo Alloy for Efficient Oxygen Evolution Reaction

Abstract

Although various highly active transition metal-based electrocatalysts have been identified for the anodic oxygen evolution reaction (OER) for alkaline water electrolysis, the necessity of a binder to coat electrocatalysts onto conductive supports affects the overall durability. Thus, developing a highly active, durable, and binder-free anode is beneficial for advancing alkaline water electrolysis for broader applications. This study presents a new yet effective surface sulfidation method for converting commercial FeNiCo alloy, Kovar, into highly active, stable, and binder-free OER electrodes. This surface sulfidation step leads not only to enhanced electrochemically active surface area but also to surface enrichment of Ni, higher oxidation states of Ni and Fe, and sulfur incorporation into lattice oxygen, which enhances the formation of (oxy)hydroxide and modulates the binding energy of *OH intermediate species. Hence, the surface sulfidized Kovar electrode demonstrated a significant enhancement in OER performance, with an overpotential as low as 261 mV at 10 mA/cm² (compared to 345 mV at 10 mA/cm² for as-received Kovar), a Tafel slope of ∼ 40 mV/dec, and robust stability over 120 hours in 1 M KOH. Thus, our surface sulfidation technique facilitates using commercial alloys as self-sufficient anodes without binders and catalysts for alkaline water electrolysis.