Engineering the Heterostructured Ni₉S₈–FeO_x 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 Ni m S n -FeO x 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 Fe 3+ and sulfur precursors can effectively trigger the phase transiting from Ni 3 S 2 to Ni 9 S 8, 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 Ni 9 S 8 –FeO x /NF-Fe 8.0 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 Ni 9 S 8 –FeO x /NF-Fe 8.0 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.