Iron–Nickel Nitride Nanostructures in Situ Grown on Surface-Redox-Etching Nickel Foam: Efficient and Ultrasustainable Electrocatalysts for Overall Water Splitting

Water splitting is widely considered to be a promising strategy for clean and efficient energy production. In this paper, for the first time we report an in situ growth of iron–nickel nitride nanostructures on surface-redox-etching Ni foam (FeNi3N/NF) as a bifunctional electrocatalyst for overall water splitting. This method does not require a specially added nickel precursor nor an oxidizing agent, but achieves well-dispersed iron–nickel nitride nanostructures that are grown directly on the nickel foam surface. The commercial Ni foam in this work not only acts as a substrate but also serves as a slow-releasing nickel precursor that is induced by redox-etching of Fe3+. FeCl2 is a more preferable iron precursor than FeCl3 for no matter quality of FeNi3N growth or its electrocatalytic behaviors. The obtained FeNi3N/NF exhibits extraordinarily high activities for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with low overpotentials of 202 and 75 mV at 10 mA cm–2, Tafel slopes of 40 and 98 mV dec–1, respectively. In addition, the presented FeNi3N/NF catalyst has an extremely good durability, reflecting in more than 400 h of consistent galvanostatic electrolysis without any visible voltage elevation.