Cobalt oxide nano dandelions on nickel foam as binder free bifunctional electrocatalyst for overall water splitting and supercapacitance

Abstract

A unique strategy that employs synthesis of dandelion-like CoO nonostructure on nickel foam (NF) through a facile one step hydrothermal method is proposed. Each dandelion is further consisting of an array of nanograss self-supported on electrode. The self-supported CoO electrode exhibited excellent electrocatalytic properties in alkaline solutions, specifically in 1 M KOH, with low overpotential of 258 and 162 mV at current density of 20 mA/cm²_geo during the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. The exceptional catalytic activity is attributed to unique morphology which result in the formation of pinning and attachment sites that allow for the growth of nanograss and the creation of stable, self-supported structure. The hierarchical 3-dimensional fluffy structures and tight adhesion between active materials and the substrate results in the preparation of self-supported electrocatalyst which offer enhanced charge transfer, accelerated diffusion of electrolyte, a large surface area with multitude of active sites, effective catalytic components, and high conductivity during the electrocatalytic process presenting small Tafel slope of 68 and 123 mV/dec for OER and HER respectively. Furthermore, the developed overall electrolyzer enables efficient full water splitting at a low cell voltage of 1.33 V at 10 mA/cm² current density. And demonstrates 100% endurance for up to 12 h at 300 mA/cm². When tested for supercapacitor performance, CoO@NF electrode demonstrates a high specific capacitance of 1592 F/g at a current density of 1 A/g in 2 M KOH solution. Moreover, it displays a remarkable energy density of 48 Wh/Kg at a high power density of 500 W/Kg. The synthesized material exhibited impressive cyclic stability by sustaining 106% capacitance retention after 5000 cycles with columbic efficiency of 98.6%. This work proposes an innovative approach for the development of single material exhibiting both electrocatalytic and energy storage high-performance characteristics.