Exploration of Local-Structure and Electrochemical Supercapacitive Performance of Hydrothermally Synthesized α-Fe2O3@Mn3O4@G Composite Electrodes

Abstract

Due to growth in human population and upsurge in the energy needs, researchers have concentrating on the development of novel/advanced electrode materials. Batteries and supercapacitors (SCs) are most significant energy storage technologies present in contemporary gadgets like smartphones, medical equipment’s, electronic devices etc. However, in comparison to SCs, batteries have higher energy densities and lower power. To increase the energy density of SCs, researchers are engaging on developing hybrid SCs based on low-cost metal oxides/carbon based composite electrodes. Herein, we apply a hydrothermal approach to synthesize graphene supported iron and manganese oxide composite for SCs for the first time. The crystalline structure, phase purity, surface morphology, chemical bonding states, elemental composition of the synthesized samples were characterized by XRD, TEM, FE-SEM, XPS and EDS analysis. In addition, XAS (XANES and EXAFS) technique is used to examine the local structure of the composite samples. After confirming all the basic characterizations, the SC electrodes were constructed using synthesized samples, exhibiting a maximum specific capacitance of about 410 F/g at 5 mV/s and 800 F/g at 1 mA/cm2 in an aqueous electrolyte, which is quite higher than that of pristine Fe2O3, pristine Mn3O4, and Fe2O3-Mn3O4 composite electrodes. Furthermore, even after 2,000 cycles, the graphene composite electrode exhibits a capacitance retention of roughly 85% and a coulombic efficiency of nearly 80%. Furthermore, an asymmetric SC device was designed employing graphene composite as the positive electrode and AC as the negative electrode and investigated their performance using CV, GCD, and EIS analyses, These SC device exhibits extraordinary device performance. As a result, the present study provides a new path to fabricate affordable and flexible SC devices for use in real time applications in near future.