Fabrication of Flexible Supercapacitor Electrode Materials by Chemical Oxidation of Iron-Based Amorphous Ribbons

Abstract

A flexible electrode constructed from Fe-based amorphous ribbons decorated with nanostructured iron oxides, representing the novelty of this research, was successfully achieved in one-step via a chemical oxidation method, using a low concentration of NaOH solution. The growth of metal oxides on a conductive substrate, which forms some metal/oxide structure, has been demonstrated to be an efficient method for increasing the charge transfer efficiency. Through the control and variation of synthetic parameters, different structures and morphologies of iron oxide were obtained, including hexagonal structures with a hollow ball shape and rhombohedral structures with rhombus-like shapes. Structural and morphological characterization methods such as X-ray diffraction and SEM morphology were used on the as-synthesized composite materials. The supercapacitor properties of the as-developed amorphous ribbons decorated with Fe2O3 nanoparticles were investigated by cyclic voltammetry, galvanostatic charge discharge, and electrochemical impedance spectroscopy. The flexible supercapacitor negative electrode demonstrates a specific capacitance of 5.96 F g−1 for the 0.2 M NaOH treated sample and 8.94 Fg−1 for the 0.4 M NaOH treated sample. The 0.2 M treated negative electrodes deliver 0.48 Wh/kg at a power density of 20.11 W/kg, and the 0.4 M treated electrode delivers 0.61 Wh/kg at a power density of 20.85 W/kg. The above results show that these flexible electrodes are adequate for integration in supercapacitor devices, for example, as negative electrodes.

One-Step Microwave-Assisted Hydrothermal Preparation of Zn-ZnO(Nw)-rGO Electrodes for Supercapacitor Applications

“…To evaluate the pseudocapacitive behavior of the Zn-ZnO(Nw)-rGO electrode, the discharge region is commonly used to obtain the most accurate data. In this case, the discharge region of the GCD curve is composed of two main domains: a rapid voltage drop domain (due to the internal resistance) and an exponentially decreasing domain attributed to the pseudocapacitive behavior resulting from redox reactions at the interface between electrodes and electrolyte [ 42 , 45 , 46 ]. In Figure 5 b, the specific capacitance (CSP) of the negative electrode, calculated from the GCD analysis, is plotted against the current density, following Equation (2) [ 47 , 48 ]: where I represents the applied current (in mA), while Δ t and Δ V represent the discharging time (in s) and discharge voltage (in V), respectively.…”