High-Efficiency Electrocatalytic Splitting of water/seawater Enabled by Ni3S2 Nanosheets Anchored on Amorphous Ni,Fe-OH with Enhanced Electron Transfer

Abstract

Water electrolysis holds significant potential for advancing the establishment of a viable green hydrogen ecosystem. However, its widespread industrial application is severely hindered by the sluggish kinetics of catalytic reactions. Enhancing the electron transfer efficiency of electrocatalysts is crucial for accelerating the kinetics of the oxygen evolution reaction (OER). To address this, a heterojunction catalyst composed of Ni₃S₂ nanosheets anchored on an amorphous Ni,Fe-OH surface was fabricated on nickel foam (NF). The Ni₃S₂/Ni,Fe-OH catalyst exhibits an exceptionally low Tafel slope (65.3 mV dec^-1) and an overpotential of 412 mV at 500 mA cm⁻². Moreover, it demonstrates outstanding long-term stability across a wide current density range of 0.05-2 A cm⁻², in both water and simulated seawater splitting. Density functional theory (DFT) calculations reveal that the higher partial density of states (PDOS) of the Ni₃S₂ catalyst facilitates accelerated electron transfer to the amorphous Ni,Fe-OH. Mechanism study identifies NiOOH as the active intermediate during the OER process. This research highlights the considerable promise of heterojunctions formed between crystalline and amorphous structures in catalysts for water and seawater electrolysis.