Band gap modified boron doped NiO/Fe3O4 nanostructure as the positive electrode for high energy asymmetric supercapacitors

Abstract

A boron doped NiO/Fe₃O₄ nanostructure was successfully synthesized by a facile one-step hydrothermal method. The boron doping was confirmed from the decreased band gap and increased electrical conductivity of the NiO/Fe₃O₄ composite. The Nyquist plot of the multimetal oxide was fitted with ZView software for detailed understanding of the effect of concentration of different metal oxides, boron doping and extensive charge–discharge cycles on the electrochemical properties of electrode materials. Very high specific capacitance of ∼1467 F g⁻¹ was achieved as the synergistic effect of low activation energy and short ion diffusion path of the electrode materials. An asymmetric supercapacitor (ASS) was fabricated with the NiO/Fe₃O₄ composite and thermally reduced graphene oxide as the positive and negative electrode, respectively. The ASS showed a large specific capacitance of ∼377 F g⁻¹ at a current density of 3 A g⁻¹. Furthermore, the ASS showed a large energy density of ∼102.6 W h kg⁻¹ and huge power density of ∼6300 W kg⁻¹ and remained ∼82% stable even after 10 000 charge–discharge cycles. Therefore, a facile hydrothermal method was demonstrated to enhance the electrochemical properties of a multimetal oxide by boron doping for the development of next generation energy storage devices.