Metal-organic framework-derived Fe/NiS heterostructure-embedded nanosheets coupled with carbon nanotubes for excellent oxygen evolution reaction

Abstract

Developing efficient and stable electrocatalysts to speed up the slow kinetics of oxygen evolution reaction (OER) is both an opportunity and a challenge. Herein, we present a metal-organic framework (MOF)-derived highly active OER catalyst (NiFe-MOF-S@CNT) composed of Fe/NiS heterostructure-embedded nanosheets interconnected by carbon nanotubes network via a direct two-step solvothermal method. The optimized NiFe-MOF-S@CNT catalyst demonstrates outstanding OER activity: it requires an ultralow overpotential of 237 mV to deliver a current density of 10 mA/cm2 (η10) with a small Tafel slope of 42.3 mV/dec, surpassing the commercial RuO2 (η10 = 295 mV) and most other transition metal catalysts. Benefiting from the mesoporous structure and large specific surface area, the MOF-derived NiFe-MOF-S@CNT nanosheets facilitate enhancing mass transfer and electrolyte penetration. Additionally, the incorporation of Fe/NiS heterostructures within the nanosheets, along with carbon nanotubes, generates interfacial effects, promoting electronic interactions and exposing more active sites, thus significantly boosting OER activity. The backbone of carbon nanotubes not only enhances conductivity but also prevents agglomeration of the metal phase, ensuring uniform dispersion of active sites. This work offers a cost-effective and green approach for synthesizing highly efficient transition metal-based sulfides and also paves the way for advancing OER electrocatalysis for various energy applications.