Metal–organic-framework-derived porous 3D heterogeneous NiFex/NiFe2O4@NC nanoflowers as highly stable and efficient electrocatalysts for the oxygen-evolution reaction

Abstract

The development of inexpensive electrocatalysts with excellent oxygen-evolution reaction (OER) performance is the key to expanding the applications of water-splitting chemistry. However, catalysts that simultaneously take into account activity and stability are generally difficult to fabricate. Herein, heterogeneous NiFe_x/NiFe₂O₄ nanoflowers were successfully embedded in an N-doped graphitic carbon (NC) matrix with a porous 3D superstructure in a simple partial oxidation process after the pyrolysis of a metal–organic framework (MOF). The optimized heterogeneous NiFe_x/NiFe₂O₄@NC nanoflower catalyst exhibited high OER performance in terms of its low overpotential of 262 mV at 10 mA cm⁻² and outstanding long-term stability (for 150 h) in 1 M KOH as the electrolyte, which are mainly ascribable to its intrinsic heterogeneous and 3D porous structure. First-principles computations confirmed that NiFe_x/NiFe₂O₄@NC requires a lower overpotential to promote OER, compared with those of single-component catalysts, which further highlights that this material is a promising low-cost and highly efficient OER electrocatalyst candidate.