Interfacial engineering of heterostructured Fe-Ni3S2/Ni(OH)2nanosheets with tailored d-band center for enhanced oxygen evolution catalysis

Hydrogen production by electrochemical water splitting suffers from high kinetic barriers in the anodic oxygen evolution reaction (OER), which limits the overall efficiency. Herein, we report a structural and electronic engineering strategy by integrating self-standing Fe-doped Ni3S2 (denoted by Fe-Ni3S2) nanosheet arrays with Ni(OH)2 subunits to form heterostructured Fe-Ni3S2/Ni(OH)2 on a Ni Foam substrate. The strong electronic interaction between the Fe-Ni3S2 and Ni(OH)2 constituents contributes abundant catalytic sites and ensures high electron transfer. Moreover, the combined experimental and theoretical study revealed that the coupling of Ni(OH)2 onto the Fe-Ni3S2 is favorable for lowering the activation energy of water oxidation for favorable OER kinetics and upshifting the Ni d-band center to facilitate the adsorption of O-containing intermediates. Consequently, the optimized Fe-Ni3S2/Ni(OH)2 hybrid catalyst exhibits excellent OER performance in alkaline electrolytes with an ultralow overpotential of 202 mV at 10 mA cm-2, a small Tafel slope of 50.6 mV dec-1, and long-term durability under high current density (0.25 A cm-2) for up to 60 h without significant deactivation. Moreover, a two-electrode Fe-Ni3S2/Ni(OH)2||Pt/C electrolyzer requires only a low voltage of 1.54 V at 10 mA cm-2 for overall water splitting. This study emphasizes the importance of interface and surface engineering in achieving highly efficient electrocatalysts.