Ionic/electronic transport properties of metal-organic framework derived 3D hierarchical Co3O4@Nickel foam electrode in mixed metal cationic electrolyte for high-energy aqueous asymmetric supercapacitor and its hydrogen evolution reaction

The 3D hierarchical Co3O4@NF electrode is fabricated by simple thermolysis of a cobalt-based metal-organic framework which was grown on nickel foam (NF). The electrochemical properties of Co3O4@NF studied in mixed electrolyte solution contains LiOH and KOH with different ratio. The electrolyte with 0.2 M LiOH and 3 M KOH provided better ionic transportation to the Co3O4@NF electrode and exhibited a specific capacity of 630.4 C g-1 at 1 A g-1. We fabricated an ultrahigh energy density asymmetric supercapacitor (ASC) having metal-organic framework derived Co3O4@NF as a positive electrode, commercial activated charcoal (CAC) as a negative electrode, and mixed cationic electrolyte of potassium hydroxide (KOH) + lithium hydroxide (LiOH). The ASC gives an energy density of 61.84 W h kg-1 at a power density of 775 W kg-1 with 72.3 % capacity retention over 10,000 cycles at 10 A g-1. The electrocatalytic performance of 3D hierarchical Co3O4@NF toward hydrogen evolution reaction also investigated, reveals a better catalytic performance for HER, which could reach 10 mA cm-2 current density at a lower overpotential of 81 mV (vs. RHE) with better stability over 24 h. The findings of this work provide insight into a new approach toward the development of high-performance energy storage devices and electrocatalysts.