Interface engineered NiFe2O4−x/NiMoO4 nanowire arrays for electrochemical oxygen evolution

[Display omitted] •Oxygen vacancy-rich NiFe2O4-x/NiMoO4 (NiFe2O4-x/NMO) nanowire arrays are prepared via ion-exchange and calcination.•NiFe2O4-x/NiMoO4 interface facilitates the charge transfer through strong electronic interaction.•NiFe2O4-x/NMO shows excellent OER performance at a high current density and good long-term stability.•In situ Raman spectroelectrochemical studies reveal rapid phase transition of NiFe2O4-x to active γ-NiOOH phase. Designing highly active and stable electrocatalysts for oxygen evolution reaction (OER) is the key to success in sustainable water splitting reaction, a sustainable route towards high purity hydrogen production. Interface engineering is one of the most effective strategies for modulating the local electronic structure of active sites to enhance catalytic activity. Herein, NiFe2O4−x nanoparticles were integrated to NiMoO4 nanowires (NiFe2O4−x/NMO) grown on nickel foam to construct an extended interface with strong electronic interactions. The NiFe2O4−x/NMO demonstrates high OER activities as manifested by a low overpotential of 326 mV at a high current density of 600 mA cm−2 and good long-term stability. The intimate interface between NiFe2O4−x and NiMoO4 is responsible for the Fe-facilitated phase transition to active γ-NiOOH phase as revealed by in situ Raman spectroelectrochemical studies. This study outlines how the interface design of integrated nanostructures can optimize the formation of active phase for enhanced catalytic activity.