Heterogeneous Ni3S2@FeNi2S4@NF nanosheet arrays directly used as high efficiency bifunctional electrocatalyst for water decomposition

Developing and designing bifunctional electrocatalysts are very important for the production of hydrogen from water electrolysis. The reasonable interface modulation can effectively lead to the optimization of electronic configuration through the interface electron transfer in the heterostructures and thus resulting in the enhanced efficiency. In this work, self-supported and heterogeneous interface-rich Ni3S2@FeNi2S4@NF electrocatalyst for overall water splitting was designed and prepared through a controllable step-wise hydrothermal process. Density functional theory calculations suggest that heterogeneous interface formed between Ni3S2 and FeNi2S4 can optimize the Gibbs free energy for H* adsorption (ΔGH*). Benefiting from the open structure of the nanosheet arrays, the abundant heterogeneous interfaces in Ni3S2@FeNi2S4@NF composite, the positive synergistic effect between Ni3S2 and FeNi2S4, and the good conductivity of foamed nickel (NF) substrate, the optimized Ni3S2@FeNi2S4@NF nanoarray catalyst displayed excellent electrocatalytic activities, the overpotential is only 83 mV and 235 mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at 10 mA cm−2, respectively. Importantly, an alkaline electrolyser directly using the Ni3S2@FeNi2S4@NF as both the anode and cathode achieved an ultralow cell voltage of 1.46 V, accompanied by outstanding stability. The performance is better than that of most other transition-metal sulfides electrocatalysts. This work may provide a useful strategy for reasonably regulating heterogeneous interfaces to effectively improve the performance of materials, thus accelerating the practical application of transition-metal sulfides electrocatalysts for overall water splitting.