α-Bi2O3 tubular rods coated on Bi2O2CO3 nanosheets for high-performance asymmetric supercapacitor applications

Abstract

Mixed phases of bismuth oxide nanostructures as an active electrode material in supercapacitor applications have recently gained huge research interest. In this study, the layered Bi₂O₂CO₃ nanosheets and the secondary phase of α-Bi₂O₃ tubular rods named Bi₂O₂CO₃/α-Bi₂O₃ heterostructure have been synthesized and utilized for supercapacitor applications. The crystal nature and microstructure of the Bi₂O₂CO₃/α-Bi₂O₃ heterostructure were initially confirmed by powder X-ray diffraction (p-XRD), Raman, UV-Vis diffuse reflectance spectroscopy (UV-DRS, absorbance), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) studies. X-ray photoelectron spectroscopy (XPS) measurements have investigated the oxidation states and chemical binding energies. Regarding the electrochemical performances, the Bi₂O₂CO₃/α-Bi₂O₃ heterostructure as electro-active material delivered a maximum specific capacitance (C_s) value of 635 F g⁻¹ at the given current density value of 1 A g⁻¹ in a conventional three-electrode mode. A coin cell type electrode has been fabricated using Bi₂O₂CO₃/α-Bi₂O₃ heterostructure, resulting in an asymmetric supercapacitor device cell (ASC), which has a C_s of 112 F g^{− 1} (at 1 A g^{− 1}) and a power density and energy density values of 515 W kg⁻¹ and 22.5 Wh kg⁻¹ respectively. The two supercapacitor electrodes in sequence effectively ignite the red-light-emitting diode (LED). Moreover, in the ASC type Bi₂O₂CO₃ /α-Bi₂O₃ heterostructure, the specific capacitance value was slightly reduced to 12.3 % by 2000 cycles, showing favourable cyclic performance and stability during the electrochemical process. Based on the above-mentioned characterization, the appropriate electrochemical performances of Bi₂O₂CO₃/α-Bi₂O₃ tubular rod heterostructures make them a promising candidate for future energy storage devices.