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.