NiO/Co3O4 nanocomposite electrode for high performance supercapacitor and oxygen evolution reaction applications

In this work, NiO/Co3O4 nanocomposite for energy storage and conversion applications has been synthesized using the hydrothermal method. The structural, optical, and morphological characteristics were analysed using X-ray diffraction, photoluminescence spectroscopy, and scanning electron microscopy techniques. As-prepared NiO/Co3O4 nanocomposite electrode exhibited a diffusion-controlled charge storage behavior with a remarkable storage capacity of 958 F/g at a current density of 1 A/g in 1 M KOH electrolyte solution. In spite after 4000 cycles at a current density of 5 A/g, the NiO/Co3O4 electrode showed higher cycling stability about 75% of its specific capacitance retention. The symmetric device exhibited a specific capacitance of 31.7 F/g at 1 A/g current density and achieved an energy density of 4.5 Wh/kg at a power density of 966 W/kg. A particularly promising outcome of this study was the device's excellent cyclic stability, retaining 63% of its capacity after 3000 discharge cycles at a current density of 5 A/g. In addition, the NiO/Co3O4 nanocomposite electrode, when employed as an oxygen evolution reaction (OER) catalyst, highlights an admirable OER activity with overpotential of 340 mV at 10 mA/cm(2) and a lower Tafel slope of 86 mV/decade. The stability tests also validate a tremendous performance of NiO/Co3O4 nanocomposite even after 10 h without obvious degradation.