Cobalt boride on clay minerals for electrochemical capacitance

Abstract

Series cobalt boride@clay mineral hybrid composites with excellent wettability to electrolytes were prepared by a simple liquid-phase reduction process based on the adsorption of Co2+ on clay minerals. Using different clay minerals of montmorillonite, kaolinite, halloysite, palygorskite, and chlorite, the influence of the structure type and morphological structure of the clay mineral on the electrochemical performance was explored. The relaxation time constant of cobalt boride@clay mineral electrodes was significantly reduced, the rate capacity and cycle stability were greatly improved. Moreover, the cobalt boride@kaolinite (CoB@Kaol) electrode possessed a satisfactory specific capacitance of 157.3 F g−1 at the current density of 0.5 A g−1 in 6 mol dm−3 KOH aqueous electrolyte, and the pseudocapacitive contribution to the entire capacity was up to 71.78% and the specific capacitance remained at 100% after 10,000 cycles, indicating remarkable electrochemical kinetics. The obtained CoB@Kaol//AC device delivered a satisfactory energy density of 15.9 W h kg−1 with the power density of 199.8 W kg−1, and a remarkable life cycle.