Band gap engineering of boron nitride by graphene and its application as positive electrode material in asymmetric supercapacitor device

Abstract

Nanostructured hexagonal boron nitride (h-BN)/reduced graphene oxide (RGO) composite is prepared by insertion of h-BN into the graphene oxide through hydrothermal reaction. Formation of the super lattice is confirmed by the existence of two separate UV–visible absorption edges corresponding to two different band gaps. The composite materials show enhanced electrical conductivity as compared to the bulk h-BN. A high specific capacitance of ∼824 F g–1 is achieved at a current density of 4 A g–1 for the composite in three-electrode electrochemical measurement. The potential window of the composite electrode lies in the range from −0.1 to 0.5 V in 6 M aqueous KOH electrolyte. The operating voltage is increased to 1.4 V in asymmetric supercapacitor (ASC) device where the thermally reduced graphene oxide is used as the negative electrode and the h-BN/RGO composite as the positive electrode. The ASC exhibits a specific capacitance of 145.7 F g–1 at a current density of 6 A g–1 and high energy density of 39.6 W h kg–1 corresponding to a large power density of ∼4200 W kg–1. Therefore, a facile hydrothermal route is demonstrated for the first time to utilize h-BN-based composite materials as energy storage electrode materials for supercapacitor applications