Ternary flower-sphere-like MnO₂-graphite/reduced graphene oxide nanocomposites for supercapacitor

Abstract

Chemical fabrication of a nanocomposite structure for electrode materials to regulate the ion diffusion channels and charge transfer resistances and Faradaic active sites is a versatile strategy towards building a high-performance supercapacitor. Here, a new ternary flower-sphere-like nanocomposite MnO2-graphite (MG)/reduced graphene oxide (RGO) was designed using the RGO as a coating for the MG. MnO2-graphite (MnO2-4) was obtained by KMnO4 oxidizing the pretreated graphite in an acidic medium (pH = 4). The GO coating was finally reduced by the NaBH4 to prepare the ternary nanocomposite MG. The microstructures and pore sizes were investigated by x-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and nitrogen adsorption/desorption. The electrochemical properties of MG were systematically investigated by the cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy in Na2SO4 solution. The MG as an electrode material for supercapacitor exhibits a specific capacitance of 478.2 and 454.6 F g−1 at a current density of 1.0 and 10.0 A g−1, respectively. In addition, the capacitance retention was 90% after 8,000 cycles. The ternary nanocomposite enhanced electrochemical performance originates from the specific flower-sphere-like morphology and coating architecture bringing higher specific surface area and lower charge transfer resistance (Rct).

Reducing the resistance for the use of electrochemical impedance spectroscopy analysis in materials chemistry

“…9,18,45,48,49 The CPE is impacted by surface roughness, chemical inhomogeneity, and a heterogeneous electrode-electrolyte interface caused by ion adsorption. 50 The magnitude of the circuit elements can provide unique information about the conductive material under investigation, such as estimate the effectiveness of electrode material enhancements, 21,22,51 indicate the presence and magnitude of the corrosion processes, 26,52,53 or evaluate the suitability of the experimental operating conditions and design. 28 For example, EIS data was recently used to probe the extent of the degradation of electrochromic devices created with different CEs.…”

“…While some very interesting specialized reviews are reporting on practical applications of EIS for bioanalytical applications, 16 to understand structure/performance relationships of metal oxides, 15 and porous electrodes, 8 the main goal of this manuscript is to bridge the gap that currently exists through a clear explanation of key terms and analysis, which are commonly not dened/explained within research manuscripts. Here, we review EIS techniques and highlight numerous practical applications within materials science, such as for analysis of self-assembled monolayers (SAMs), 9,17,18 supercapacitors, [19][20][21][22] dye-sensitized solar cells (DSSCs), 23,24 conductive coatings, [25][26][27] sensors, 28,29 porous electrodes for different applications, [30][31][32] and other "smart" materials. 7,33,34 Very recent exciting literature examples that applied EIS to characterize, optimize or fully understand the performance of the material include analysis of on-skin or wearable sensors, 35,36 "green" microbial fuel cells, 37 and biosensors of SARS-CoV-2 antibodies.…”

Perspective Chapter: Graphene Based Nanocomposites for Supercapacitor Electrodes

“…Supercapacitor is an attractive electrochemical device that fulfills the requirement of all advanced electronic and electrical devices [1]. Supercapacitors have gained a lot of attention and have been employed in various fields, including various electronic devices, power supplies, and electric vehicles due to their high-power densities, rapid charge/discharge rates, and exceptional cycling stability [2][3][4][5]. Supercapacitors are divided into two categories depending on their charge storage capacity: 1) electrical double-layer capacitors (EDLCs) made of various carbon-based materials, while 2) pseudocapacitors made of transition metal oxides and other conductive polymers as active materials [6][7][8][9].…”

Electrostatic flocking MnO 2 nanofiber electrode for long cycling stability supercapacitors

“…The active materials are generally powder state, which should be doped into the polymer binder (eg, polyvinylidene fluoride [PVDF], polytetrafluoroethylene [PTFE]) for coating on the metal current collector (eg, aluminum or copper foil). However, these polymer binders do not only decrease the electrochemical area of active materials but also enhance the ionic transport resistance from electrolyte to active materials 3 . To overcome these defects, one promising strategy is to directly deposit active materials on current collector (eg, Ni foam or titanium plate) for application in the supercapacitor.…”

“…However, these polymer binders do not only decrease the electrochemical area of active materials but also enhance the ionic transport resistance from electrolyte to active materials. 3 To overcome these defects, one promising strategy is to directly deposit active materials on current collector (eg, Ni foam or titanium plate) for application in the supercapacitor. For example, the MnO 2 was deposited on Ni foam by the hydrothermal method.…”