In-Situ Grown, Passivator-Modulated Anodization Derived Synergistically Well-Mixed Ni–Fe Oxides from Ni Foam as High-Performance Oxygen Evolution Reaction Electrocatalyst

A simple one-step passivator-modulated nickel foam (NF) anodization process was developed to fabricate synergistically well-mixed NiO/α-Fe2O3@NF, which was demonstrated a high efficiency electrocatalyst for oxygen evolution reaction (OER), exhibiting ultralow overpotentials and excellent stability at high current densities. The NiO/α-Fe2O3@NF composite electrode, with NiO and α-Fe2O3 well-mixed at nanoscale for much enhanced synergistic effects, exhibited extraordinary electrochemical activities with ultralow overpotentials of 244 and 334 mV at current densities of 50 and 500 mA/cm2, respectively, for the OER in 1 M KOH. The NiO/α-Fe2O3@NF composite electrode was further tested as both the cathode and anode for overall water splitting, and achieved low working cell voltages of 1.76 and 1.99 V at the current densities of 50 and 500 mA/cm2, respectively, outperforming the pairing of Pt/C@NF and IrO2@NF, 1.79 and 2.08 V, correspondingly. The stability of the NiO/α-Fe2O3@NF electrode was also outstanding, experiencing only a minor chronoamperometric decay of 5.6% after a continuous operation at 500 mA/cm2 for 24 h. The success of the present catalyst design was attributed to the strong positive synergistic effects between the well mixed NiO and α-Fe2O3 at nanoscale and between the nonconductive mixed oxide catalyst and the conductive nickel foam support.