Designing 3D Ternary Hybrid Composites Composed of Graphene, Biochar and Manganese Dioxide as High-Performance Supercapacitor Electrodes

Abstract

Biochar derived from waste biomass has proven to be an encouraging novel electrode material in supercapacitors. In this work, luffa sponge-derived activated carbon with a special structure is produced through carbonization and KOH activation. The reduced graphene oxide (rGO) and manganese dioxide (MnO2) are in-situ synthesized on luffa-activated carbon (LAC) to improve the supercapacitive behavior. The structure and morphology of LAC, LAC-rGO and LAC-rGO-MnO2 are characterized by the employment of X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), BET analysis, Raman spectroscopy and scanning electron microscopy (SEM). The electrochemical performance of electrodes is performed in two and three-electrode systems. In the asymmetrical two-electrode system, the LAC-rGO-MnO2//Co3O4-rGO device shows high specific capacitance (SC), high-rate capability and excellent cycle reversibly in a wide potential window of 0–1.8 V. The maximum specific capacitance (SC) of the asymmetric device is 586 F g−1 at a scan rate of 2 mV s−1. More importantly, the LAC-rGO-MnO2//Co3O4-rGO device exhibits a specific energy of 31.4 W h kg−1 at a specific power of 400 W kg−1. Overall, the synergistic effect between the ternary structures of microporous LAC, rGO sheets and MnO2 nanoparticles leads to the introduction of high-performance hierarchical supercapacitor electrodes.

Electrode Materials, Structural Design, and Storage Mechanisms in Hybrid Supercapacitors

“…Electron and ion transport efficiency for charge storage in Co 3 O 4 -based pseudocapacitors mainly depends on electrode properties such as surface area, morphology, and alignment of nanocrystalline phases [ 101 , 102 ]. In the past decade, numerous Co 3 O 4 nanostructures have been fabricated and tested for superior performance in the field of energy storage [ 103 , 104 , 105 , 106 , 107 , 108 , 109 , 110 ]. For example, Yang et al [ 109 ] synthesized Pr-doped Co 3 O 4 nanoflakes, which exhibited a high specific capacity of 640 C g −1 at a current density of 2 A g −1 , and 64% of the capacity retention at a high current density of 10 A g −1 .…”