In Situ Formed Edge-Rich Ni₃S₂-NiOOH Heterojunctions for Oxygen Evolution Reaction

Developing highly active, earth-abundant, and durable electrocatalysts is desired but challenging for oxygen evolution reaction (OER). In this work, we design an electrocatalyst of the edge-rich nickel sulfide arrays on the nickel foam (Ni3S2 NSs-NF) by a facile yet efficient wet-chemical method. Benefiting from the three-dimensional nanostructure with numerous active edges, the prepared Ni3S2 NSs-NF exhibits superior OER performance in alkaline conditions. An in-depth study reveals that the real active sites toward OER are the in situ formed heterogenous Ni3S2-NiOOH. Density functional theory (DFT) calculations indicate the density of state (DOS) of the Ni3S2-NiOOH heterojunction near the Fermi level is enhanced, contributing to higher electronic conductivity. As a result, the Ni3S2 NSs-NF with abundant Ni3S2-NiOOH heterojunctions exhibits an efficient electrochemical activity toward OER in alkaline conditions. The Ni3S2 NSs-NF electrode shows an overpotential of 244 mV at 10 mA cm-2 with a Tafel slope of 75 mV dec-1 and possesses ultrastable performance even at 100 mA cm-2.