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

Abstract

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 (ΔG_H*). 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.

Keywords: FeNi(2)S(4); HER; Ni(3)S(2); OER; Overall water splitting.