Nitrogen-doped carbon decorated-Ni3Fe@Fe3O4 electrocatalyst with enhanced oxygen evolution reaction performance

11 figures, 2 tables.-- Supplementary information available.
High performance, durable and inexpensive electrocatalyst for oxygen evolution reaction (OER) is of great importance for tenable hydrogen production via water electrolysis. Although spinel oxides (AB2O4, A, B = metal) represent a class of promising candidates for OER, their intrinsically poor electrical conductivity impacts their electrochemical performance. Herein, we employed a facile approach to transform an intrinsically low active NiFe2O4 into nitrogen-doped carbon decorated Ni3Fe@Fe3O4 catalyst with improved activity and stability for alkaline OER. Initially, a pristine NiFe2O4 octahedron-like structure was synthesized by a hydrothermal route. Then, series electrocatalysts were prepared by incorporating the pristine NiFe2O4 with different dopamine concentrations via in-situ polymerizations of dopamine followed by carbonization. The morphology, crystalline structure, and chemical composition of the catalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma (ICP). The OER electrocatalysis performance was measured in a standard three-electrode system. The effect of the carbonized dopamine on the electrocatalytic activity and structure of the NiFe2O4 precursor was systematically investigated. Among several NiFe electrocatalysts, the one with 10 wt% of dopamine (NiFe/NC10%) exhibited a relatively higher catalytic activity for OER tested in 1.0 M KOH; unveiled low overpotential (350 mV at 10 mAcm−2 current density), a low Tafel slope (56 mVdec−1), low charge transfer resistance, relatively higher electrochemically active surface area. Most prominently, it remained stable for at least 12 h. This work provides a new perspective for functionalizing metal oxides and affords a facile synthesis approach, low-cost, high-performance, and robust electrocatalyst for alkaline OER electrodes.
Financial support from the European Union's Horizon 2020 Research and Innovation programme under the Marie Skłodowska-Curie Actions–Innovative Training Networks (MSCA-ITN) Grant Agreement 813748 are gratefully acknowledged.