Precise engineering of Fe3O4/MWCNTs heterostructures for high-performance supercapacitors

Abstract

The development of electrode materials with well-defined interfaces plays a vital role on improving the electrochemical performance of supercapacitors. The hybridization of conductive carbon materials with metal oxides is recommended to fabricate improved supercapacitor electrodes. In this work, catalytic chemical vapor deposition (CCVD) and solvothermal methods were utilized to synthesize a Fe3O4/MWCNTs heterostructure with tuned size and morphology. The heterostructure-based electrode showed supreme specific capacitance, energy density, and cycling stability. The size of Fe3O4 as well as the diameter and the number of walls of the functionalized MWCNTs were optimized. Various characterization techniques such as Scanning Electron Microscopy (SEM) combined with Energy Dispersive X-ray (EDX) spectroscopy, Transmission Electron Microscopy (TEM), X-ray diffraction spectroscopy (XRD), and Raman Spectroscopy were utilized to explore the structural and surface properties of the engineered heterostructures. The electrochemical measurements were carried out in 6 M KOH for all synthesized electrodes. The Fe3O4/MWCNTs heterostructure showed a specific capacitance of 492.3 F/g, energy density of 115.55 Wh/Kg at 1 A/g, and capacitance retention of 165.7 % after 1000 cycles. The specific capacitance of the electrodes was further calculated using CV measurement achieving 921.3 F/g at 10 mV/s for the Fe3O4/MWCNTs heterostructure. The excellent electrochemical performances of MWCNTs/Fe3O4 heterostructures were mainly due to the homogenous distribution of Fe3O4 nanoparticles with multivalent oxidation states on the surface of MWCNTs. This led to faster surface oxidation-reduction reactions and consequently, higher reversible capacity and ultrahigh energy density in addition to improved cyclability. This work sheds light on the possibility of precisely controlling Fe3O4/MWCNTs heterostructure electrodes for high-performance energy storage applications.