Engineering the Heterostructured Ni9S8–FeOx Nanoarrays for Electrocatalytic (Sea)Water Splitting

Constructing transition metal multiphase composites can improve the electrocatalytic efficiency of (sea)water splitting via interfacial interaction between adjacent active sites. Herein, the self-supporting NimSn-FeOx heterostructure is in situ grown on nickel foam (NF) through a corrosion engineering approach, which displays abundant dendritic array structures, endowing the material with abundant active sites and high electrocatalytic active area. The control of introducing Fe3+ and sulfur precursors can effectively trigger the phase transiting from Ni3S2 to Ni9S8, generating more S vacancies, which could reduce the reaction energy barrier and improve the electrocatalytic performance. Simultaneously, the presence of Fe–S bonding at the sulfide/oxide interface brings a strong electronic interaction, which enables the tuning of the adsorption energy of the reaction intermediates and accelerates the catalytic reaction kinetics. As a result, the Ni9S8–FeOx/NF-Fe8.0 catalyst presents low overpotentials of 159 mV and 190 mV for oxygen evolution reaction at 100 mA cm–2 under 1 M KOH solution and simulated seawater conditions, respectively. The overall water splitting incorporating the Ni9S8–FeOx/NF-Fe8.0 as both anode and cathode provides the potential of 1.707 V in 1 M KOH and 1.794 V in simulated seawater at 100 mA cm–2. This research furnishes an efficient strategy toward the design of advanced transition metal heterogeneous composites with strong interfacial interaction for (sea)water splitting.