Ionic liquid–controlled growth of bifunctional NiCo2O4 nanostructures with different dimensionalities on carbon cloth for oxygen evolution reaction and asymmetric supercapacitor

Abstract

The design structure of electrocatalysts/electrode materials is important for achieving highly efficient energy conversion and storage in electrochemical energy devices. We report the synthesis of 3D NiCo2O4 hierarchical nanocactus arrays (NiCo2O4–NC) comprising 1D nanowires and 2D nanoflakes on carbon cloth by controlling the concentration of ionic liquid (IL) 1–dodecyl–3–methylimidazolium acetate ([C12MIm]Ac). For both oxygen evolution reaction (OER) and asymmetric supercapacitors (ASC), NiCo2O4–NC shows enhanced electrochemical performance. Impressively, for the OER process, NiCo2O4–NC exhibits an overpotential of 294 mV at 10 mA cm−2, Tafel slope of 77 mV dec−1, and superior stability. As a supercapacitor electrode, NiCo2O4–NC exhibits a high specific capacitance of 1842 F g−1 at 1 A g−1, outstanding rate capability, and superior cycling stability. Moreover, NiCo2O4–NC–based ASC produces a high energy density of 46.1 Wh kg−1 at power density of 557.4 W kg−1. The outstanding electrochemical performance is attributed to the distinct structure of NiCo2O4–NC with the merits of both 1D nanowires and 2D nanoflakes. This work not only offers an effective mean to design nanostructured metal oxide arrays with improved electrochemical performance but also lays the foundation of studying the application potential of ILs in the synthesis of multifunctional materials.