Ganesh Kumar Veerasubramani

Electrochemical performance of an asymmetric supercapacitor based on graphene and cobalt molybdate electrodes

In this article, we report the fabrication and electrochemical performance of asymmetric supercapacitors (ASCs) based on a reduced graphene oxide (rGO) negative electrode and a cobalt molybdate (CoMoO4) positive electrode. The rGO and CoMoO4 electrode materials were synthesized by hydrothermal and sonochemical methods, respectively. Physico-chemical characterization techniques such as X-ray diffraction, field-emission scanning electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, and nitrogen adsorption–desorption isotherm analysis were used to characterize the electrode materials. The rGO nanosheets and CoMoO4 nanostructures delivered a specific capacitance of about 168.8 and 98.34 F g−1, respectively measured in a three electrode system. The rGO‖CoMoO4 ASC device demonstrated a maximum specific capacitance of 26.16 F g−1 (at a current density of 0.5 mA cm−2), an energy density of 8.17 W h kg−1, and a maximum working voltage of 1.5 V. The fabricated device possessed excellent capacitance retention of about 85% after 4000 cycles (at a current density of 1.0 mA cm−2) suggesting the superior cyclic stability of the fabricated ASC device.

One-pot hydrothermal synthesis, characterization and electrochemical properties of CuS nanoparticles towards supercapacitor applications

In this article, we have investigated the electrochemical properties of CuS nanoparticles for supercapacitor applications. The CuS nanoparticles are prepared by a facile one-pot hydrothermal approach using copper nitrate and thiourea as starting materials. The x-ray diffraction study revealed the formation of covellite CuS. The field-emission scanning electron microscope studies suggested the formation of cubic shaped CuS nanoparticles. The electrochemical studies such as cyclic voltammetry, galvanostatic charge-discharge analysis and electrochemical impedance spectroscopy confirmed the pseudocapacitive nature of the CuS electrodes. The CuS electrode shows a specific capacitance of about 101.34 F g−1 from the cyclic voltammetry at a scan rate of 5 mV s−1. The electrochemical impedance spectra analyzed using Nyquist plot confirmed the pseudocapacitive behavior of the CuS electrodes.

Liquid electrolyte mediated flexible pouch-type hybrid supercapacitor based on binderless core–shell nanostructures assembled with honeycomb-like porous carbon

The current challenges in the usage of liquid electrolyte in energy storage devices are closely correlated with the flexibility and portability of the devices. In this paper, a highly flexible, pouch-type hybrid supercapacitor in liquid electrolyte based on a binderless cobalt hydroxide–cobalt molybdate (CoMoO4@Co(OH)2) core–shell structure (prepared by electrochemical deposition; ECD) sandwiched with honeycomb-like porous carbon derived from laboratory waste tissue paper (prepared by a hydrothermal reaction and carbonization) is presented. Its excellent hierarchical core–shell structure and honeycomb-like porous carbon results in a large electrochemically active surface area, which yields a high areal capacity of 265 μA h cm−2 and excellent specific capacitance of 227 F g−1 in liquid potassium hydroxide (KOH) electrolyte with excellent cyclic stability. An assembled pouch-type hybrid supercapacitor using the prepared core–shell structure as the positive electrode and porous carbon as the negative electrode shows an extended working voltage of 1.5 V in 2 M KOH electrolyte, which stores a maximum energy density of 167.5 μW h cm−2. Interestingly, the fabricated pouch-type supercapacitor shows an excellent flexibility under different bending conditions and exhibits remarkable cyclic stability with >98% capacitance retention even after long cycles. Furthermore, the capability of the device is demonstrated by integrating it with a solar cell to drive the various types of light-emitting diodes (LEDs) and seven segment displays for self-powered applications.

Effective use of an idle carbon-deposited catalyst for energy storage applications

Global warming is primarily a problem of excessive carbon dioxide (CO2) in the atmosphere, which acts as a blanket, trapping heat and warming the planet. One of the inevitable reactions during syngas (SNG) production by the dry reforming reaction (DRR) of hydrocarbons is the deposition of carbon over the catalyst which can be eliminated as anthropogenic CO2. This is the main obstacle for SNG production during the DRR, diminishes the performance of the catalysts and enhances the CO2 formation which leads to global warming. In this study, for the first time, we present a novel approach to use the carbon-deposited catalyst formed during the DRR as an effective electrode material for supercapacitor applications. This disposable carbon-deposited catalyst shows ∼22 times higher capacity than the bare catalyst and acts as a positive electrode for asymmetric supercapacitors. The fabricated supercapacitor device works with an extended voltage of 1.6 V and exhibits an excellent electrochemical performance. Moreover, serially connected supercapacitor devices could power up various types of LEDs and UV light sensors.