Gas-liquid diffusion directed rational synthesis of Fe-doped NiCo2O4 nanoflower for efficient oxygen evolution reaction

Abstract

Distinct from the traditional synthesis of NiCo2O4 nanoflowers from hydrothermal approach. Herein a facile gas-liquid diffusion method was exploited to prepare NiCo2O4 and Fe-doped NiCo2O4 nanoflower under ambient condition for oxygen evolution reaction (OER). The remarkable nanoflowers was generated by diffusing ammonia to the homogeneous solution of cobalt and nickel sulfate salt with slight amount of Fe sulfate salt to form a heterogeneous precipitation, followed by pyrolysis to afford the final product of NiCo2O4 or Fe-doped NiCo2O4. The remarkable feature of NiCo2O4 displays a spherical nanoflower morphology composed of lamellar structure with excellent dispersibility and greatly prompt the electron transfer and enable a high activity. By varying the ratio of Ni to Fe to 9:1, a superior OER performance with overpotential of 256 mV and Tafel slope of 69 mV·dec−1 at 10 mA·cm−2 was obtained. We attribute the superior performance to the excellent gas and ion transport channels due to the unique nanoflower structure as well as the well optimized electronic structure derived from Fe doping. Besides, we tentatively propose a detailed formation process for the formation of this nanoflower structure based on co-precipitation reaction. In conclusion, this approach offers a facile and efficient way for the preparation of high-performance ternary mixed metal oxides nanostructure which enable its large-scale production of OER catalyst.