Nanostructured Fe-Doped\nNi<sub>3</sub>S<sub>2</sub> Electrocatalyst for the Oxygen Evolution\nReaction with High Stability\nat an Industrially-Relevant Current Density

A novel oxygen evolution reaction (OER) electrocatalyst\nwas prepared\nby a synthesis strategy consisting of the solvothermal growth of Ni<sub>3</sub>S<sub>2</sub> nanostructures on Ni foam, followed by hydrothermal\nincorporation of Fe species (Fe–Ni<sub>3</sub>S<sub>2</sub>/Ni foam). This electrocatalyst displayed a low OER overpotential\nof 230 mV at 100 mA·cm<sup>–2</sup>, a low Tafel slope\nof 43 mV·dec<sup>–1</sup>, and constant performance at\nan industrially relevant current density (500 mA·cm<sup>–2</sup>) over 100 h in a 1.0 M KOH electrolyte, despite a minor loss of\nFe in the process. Based on a detailed characterization by (in situ)\nRaman spectroscopy, (quasi-in situ) XPS, SEM, TEM, XRD, ICP-AES, EIS,\nand <i>C</i><sub>dl</sub> analysis, the high OER activity\nand stability of Fe–Ni<sub>3</sub>S<sub>2</sub>/Ni foam were\nattributed to the nanostructuring of the surface in the form of stable\nnanosheets and to the combination of Ni<sub>3</sub>S<sub>2</sub> granting\nsuitable electrical conductivity with newly formed NiFe-based (oxy)hydroxides\nat the surface of the material providing the active sites for OER.