Fe-doping engineering of hierarchical NiS/Co_2.67S₄ nanoarrays as bifunctional electrocatalysts toward high-efficiency...

Transition metal sulfides (TMS) have emerged as promising electrocatalysts for overall water splitting (OWS), owing to their cost-effectiveness, inherent abundant active sites and tunable electronic structures. However, several issues, e.g., high overpotentials originating from the sluggish water dissociation, shielding of active sites and mass transfer resistance, as well as the modest long-duration electrocatalytic stability, are still enormous challenges. For this, the superwetting leafy Fe-doped nickel sulfide/cobalt sulfide nanoarrays on nickel foam (NF) (denoted as Fe-NiS/Co_2.67S₄/NF) are successfully designed and fabricated by the template-involved avenue. The interfacial electron re-arrangement of NiS/Co_2.67S₄ induced by Fe doping optimizes the charge density distribution near the d-band center, promoting the adsorption-desorption of reaction intermediates. Additionally, the unique leafy architecture exhibits superhydrophilic sur-/interfaces, enabling efficient electrolyte penetration and accelerated bubble release during in-situ gas generation. Thereby, the advantages validated by comprehensive physical experiments and theoretical calculations endow Fe-NiS/Co_2.67S₄/NF with superior electrocatalytic performance in both hydrogen evolution reaction and oxygen evolution reaction, along with remarkable operational stability during high-current-density overall water electrolysis (1000 h at 500 mA cm^-2). This work, besides the well-established reliable methodology for TMS nanoarrays, offers in-depth insights into catalytic optimization of electrocatalysts for high-efficiency OWS.