Sodium Tartrate-Assisted Synthesis of High-Purity NiFe2O4 Nano-Microrods Supported by Porous Ketjenblack Carbon for Efficient Alkaline Oxygen Evolution.

Abstract

Herein, a simple two-step synthetic method was developed for the synthesis of NiFe2O4 nano-microrods supported on Ketjenblack carbon (NiFe2O4/KB). A sodium tartrate-assisted hydrothermal method was employed for the synthesis of a NiFe-MOF/KB precursor, which was then pyrolyzed under N2 at 500 °C to yield NiFe2O4/KB. Benefiting from the presence of high-valence Ni3+ and Fe3+, high conductivity, and a large electrochemically active surface area, NiFe2O4/KB delivered outstanding OER electrocatalytic performance under alkaline conditions, including a very low overpotential of 258 mV (vs RHE) at 10 mA cm-2, a small Tafel slope of 43.01 mV dec-1, and excellent durability in 1.0 M KOH. Density functional theory calculations verified the superior alkaline OER electrocatalytic activity of NiFe2O4 to IrO2. While both catalysts possessed a similar metallic ground state, NiFe2O4 offered a lower energy barrier in the rate-determining OER step (*OOH → O2) compared to IrO2, resulting in faster OER kinetics.