Manipulating Electron Redistribution in the FeNi₂S₄/Ni₃S₂ Heterostructure for Enhanced Alkaline Water Electrolysis

Developing efficient bifunctional electrocatalysts for enhanced alkaline water electrolysis remains a challenge. Herein, the density functional theory (DFT) calculation is proposed to preanalyze the electron redistribution by introducing Co heteroatom doping and heterostructure engineering in cobalt-doped FeNi 2 S 4 (Co-FeNi 2 S 4 )/nickel sulfide (Ni 3 S 2 ). The mushroom-like Co-FeNi 2 S 4 /Ni 3 S 2 is constructed on nickel foam (Co-FeNi 2 S 4 /Ni 3 S 2 /NF) through a two-step solvothermal method. Resultantly, the optimized Co-FeNi 2 S 4 /Ni 3 S 2 /NF shows excellent electrochemical activities, affirmed by the significantly low overpotentials of 133 mV for the hydrogen evolution reaction (HER) at 10 mA cm –2, 261 mV for the oxygen evolution reaction (OER) at 50 mA cm –2, and 1.58 V for overall water splitting at 10 mA cm –2 . In situ Raman spectra and DFT calculation results collectively unveil the reasons for the enhanced electrocatalytic activity. Specifically, introducing Co doping and heterostructures in catalysts not only manipulates electron redistribution and optimizes the d-band center (ε d ) level to further accelerate electrocatalytic kinetics but also reveals the interfacial Co atoms responsible for the HER and Ni/Fe (oxy)hydroxides at the surface, facilitating the OER. This work provides elaborate insights into the manipulation of electron redistribution in electrocatalysts and is expected to guide the synthesis of other efficient electrocatalysts.