Synthesis of In2O3 nanostructures with different morphologies as potential supercapacitor electrode materials

Abstract

In this study performed using a chemical vapor deposition (CVD) system, one-dimensional (1-D) single crystal indium oxide (In2O3) nanotowers, nanobouqets, nanocones, and nanowires were investigated as a candidate for a supercapacitor electrode material. These nanostructures were grown via Vapor–Liquid–Solid (VLS) and Vapor–Solid (VS) mechanisms according to temperature differences (1000–600°C). The morphologies, growth mechanisms and crystal structures of these 1-D single crystal In2O3 nanostructures were defined by Field Emission Scanning Electron Microscopy (FESEM), High Resolution Transmission Electron Microscopy (HR-TEM), X-Ray Diffraction (XRD) and Raman Spectroscopy analyses. The elemental analyses of the nanostructures were carried out by energy dispersive X-Ray Spectroscopy (EDS); they gave photoluminescence (PL) spectra with 3.39, 2.65, and 1.95eV band gap values, corresponding to 365nm, 467nm, and 633 wavelengths, respectively. The electrochemical performances of these 1-D single crystal In2O3 nanostructures in an aqueous electrolyte solution (1M Na2SO4) were determined by Cyclic Voltammetry (CV), Galvanostatic Charge Discharge (GCD) and Electrochemical Impedance Spectroscopy (EIS) analyses. According to GCD measurements at 0.04mAcm−2 current density, areal capacitance values were 10.1mFcm−2 and 6.7mFcm−2 for nanotowers, 12.5mFcm−2 for nanobouquets, 4.9mFcm−2 for nanocones, and 16.6mFcm−2 for nanowires. The highest areal capacitance value was observed in In2O3 nanowires, which retained 66.8% of their initial areal capacitance after a 10000 charge-discharge cycle, indicating excellent cycle stability.