Partial Sulfidation Strategy to NiFe-LDH@FeNi2S4 Heterostructure Enable High-Performance Water/Seawater Oxidation

The development of a high-performance electrocatalyst for oxygen evolution reaction (OER) is imperative but challenging. Here, a partial sulfidation route to construct Ni2Fe-LDH/FeNi2S4 heterostructure on nickel foam (Ni2Fe-LDH/FeNi2S4/NF) by adjusting the hydrothermal duration is reported. The heterostructures afford abundant hydroxide/sulfide interfaces that offer plentiful active sites, rapid charge and mass transfer, favorable adsorption energy to oxygenated species (OH- and OOH) evidenced by the density functional theory calculations, which synergistically boost the alkaline water oxidation. In the 1.0 m KOH solution, Ni2Fe-LDH/FeNi2S4/NF exhibits an excellent OER catalytic activity with a much smaller overpotential (240 mV) to reach the current density of 100 mA cm(-2) than single-phase Ni2Fe-LDH/NF (279 mV) or FeNi2S4/NF (271 mV). More impressively, 2000 cycles of cyclic voltammetry scan for water oxidation results in the formation of a sulfate layer over the catalyst. The corresponding post-catalyst demonstrates better OER activity and durability than the initial one in the alkaline simulated seawater electrolyte. The post-Ni2Fe-LDH/FeNi2S4/NF delivers smaller overpotential (250 mV) at 100 mA cm(-2) and longer stability time than the original form (260 mV). The post-formed sulfate passivating layer is responsible for the outstanding corrosion resistance of the salty-water oxidation anode since it can effectively repel chloride.