Ganesh Chandra Nayak

Effect of waste cellulose fibres on the charge storage capacity of polypyrrole and graphene/polypyrrole electrodes for supercapacitor application

This paper explores the possibility of dealing with two major challenges of the contemporary world, i.e., waste management and storage of energy. This study presents the extraction and application of cellulose (from waste paper) based composites for supercapacitor electrodes with a view to mitigate the energy crisis. In situ polymerization is used for the synthesis of benign composites comprising cellulose, polypyrrole (PPy) and graphene. It has been observed that inclusion of cellulose in PPy increases the specific capacitance by 318% with moderate energy density and appreciably high power density compared to PPy alone. Similar results are obtained for graphene/PPy/cellulose composites where a 273% increase of specific capacitance is observed with the incorporation of cellulose in graphene/PPy composites without deteriorating the cyclic stabilities of the electrode materials.

Magical Allotropes of Carbon: Prospects and Applications

ABSTRACT The invention of carbon and its allotropes have transformed the electronic and optoelectronic industry due to their encouraging properties in a large spectrum of applications. The interesting characteristic of carbon is its ability to form many allotropes due to its valency. In recent decades, various allotropes and forms of carbon have been invented, including fullerenes, carbon nanotubes (CNTs), and graphene (GR). Since the inception of nanotechnology, carbon allotropes-based nanocomposites have become a leading sector of research and advancement due to their unique bonding properties. Fullerenes and CNTs-based polymer nanocomposites have attracted significant research interest due to their vast applications in every sphere of science and technology. Current research impetus reveals that carbon and its allotropes have revolutionized the industry and academia due to their fascinated properties. Recent advances in various aspects of graphene, CNTs, graphene nanoribbons, fullerenes, carbon encapsulates, and their nanocomposites with polymeric materials and their different applications are reported in this review article. Also, current status and future prospects of graphene-based polymer nanocomposites are presented in common along with proper citations extracted from the scientific literature. Moreover, this article is a unique collection of vital information about GR, CNTs, fullerenes, and graphene-based polymer nanocomposites in a single platform.

A V2O5 nanorod decorated graphene/polypyrrole hybrid electrode: a potential candidate for supercapacitors

Vanadium pentoxide (V2O5) nanorod decorated graphene polypyrrole nanocomposites have been synthesized successfully by a facile hydrothermal process for supercapacitor (SC) applications. The morphological study revealed the successful decoration of V2O5 nanorods and polypyrrole (PPy) within the intergallery of graphitic materials due to their high degree of propensity for intercalation which leads to the formation of mesoporous 3D nanostructures. These mesoporous structures can efficiently allow fast diffusion and ion transport at the electrode–electrolyte interface towards high electrochemical utilization and superior performance. Here, decoration of V2O5 within a polymer matrix along with a graphitic material renders different electrical profiles by virtue of their electron hopping within nanocomposites. Galvanostatic charging discharging revealed that VGP was found to be superior with a maximum specific capacitance of 787 F g−1 at a current density of 1 A g−1 using KCl as an electrolyte. These observations were also confirmed by electrochemical measurements through CV and EIS studies. Furthermore, cyclic stability performed for 5000 consecutive cycles also substantiate their high durability and high power delivery uptake. Thus, considering all such key features, V2O5 based nanocomposites can be suitable for SC applications.

Template-free single pot synthesis of SnS2@Cu2O/reduced graphene oxide (rGO) nanoflowers for high performance supercapacitors

A template-free one-pot hydrothermal route was adopted for the facile synthesis of SnS2@Cu2O/reduced graphene oxide (rGO) nanoflowers for supercapacitor electrode materials. The structure and morphology was established using XRD, FTIR, XPS, TEM and FESEM. The electron transfer between the two metal centers in the ternary nanocomposite resulted in an ultra-high specific capacitance of 1800 F g−1 at 0.6 A g−1 in 1 M KOH in a three electrode testing environment. The specific capacitance in a two electrode set-up in 1 M TEABF4 (in acetonitrile) was measured to be 1290 F g−1 at the fixed current density (CD) of 1 A g−1 and about 90% of the specific capacitance was retained after 1000 consecutive charge–discharge cycles. This ultra-high specific capacitance was complemented by the high energy density of 160.0 W h kg−1 and the superior power delivery rate of 3999.54 W kg−1 at the CD of 10 A g−1 in a three electrode aq. KOH set-up. However, in the two-electrode configuration with organic system (TEABF4 in acetonitrile), the composite showed an energy density of 458.67 W h kg−1 at the high power delivery rate of 1600 W kg−1 and a current density of 1 A g−1. These remarkable electrochemical properties show the potential of this ternary nanocomposite for the fabrication of high performance supercapacitors.

Hierarchical self-assembled nanoclay derived mesoporous CNT/polyindole electrode for supercapacitors

A series of self-assembled and open interconnected mesoporous CNT/polyindole (Pind) electrodes were synthesized by a facile in situ & ex situ approach in the presence of layered silicate material. In the present study, the presence of nanoclay and its electrochemical performance is explored on the imparted hierarchical structure of CNT/Pind (CI) system. The microstructural evolution and coating of Pind on CNT and the nanoclay sheet revealed the formation of a high surface area interconnected mesoporous structure which can efficiently allow easy penetration and rapid transport of electrolyte ions for an improved electrochemical performance. Cyclic voltammetry (CV) analysis at 10 mV s−1 revealed the in situ and ex situ incorporation of the nanoclay to the CNT/Pind system exhibited a 258% and 136% increase in the specific capacitance of the ternary nanocomposite, respectively. These observations were very consistent with the 148% increased specific capacitance of NI (nanoclay/Pind) as compared to Pind. Galvanostatic charging–discharging (GCD) and electrochemical impedance spectroscopy (EIS) also confirmed the improved electronic conductivity and cyclic stability of electrode material. In situ CNI (i.e. CNT/nanoclay/Pind) displayed a better electrochemical performance than ex situ CIN (i.e. CNT/Pind/nanoclay) and other related systems. That the electrode exhibited 96% of the initial specific capacitance retention after 2000 cycles also suggests a high cyclic stability and power delivery uptake of electrode material. It is believed that a nanoclay tailored CNT/Pind nanocomposite can effectively promote their high utilization for SC application.

Nanoclay based graphene polyaniline hybrid nanocomposites: promising electrode materials for supercapacitors

Nanoclay based graphene polyaniline (PANI) hybrid nanocomposites were synthesized by both in situ and ex situ approaches and the effect of the nanoclay on the energy storage capability was explored. The coating status of PANI over the surface of both graphene and nanoclay was analyzed with SEM & FESEM. The electrochemical properties of all the samples were analyzed by cyclic voltammetry, charging discharging measurements and electrochemical impedance spectroscopy using 1 M aq. KCl as the electrolyte and a conventional three electrode system. All the results revealed a better electrochemical performance of the nanoclay based hybrid nanocomposites as compared to other systems. It was found that the in situ product exhibited a maximum specific capacitance of 375 F g−1 at a scan rate of 10 mV s−1 which was higher than other similar systems. We have also explored the effect of sequential addition of the nanoclay towards the capacitive performance.

Synthesis and characterization of CuO nanoparticles using strong base electrolyte through electrochemical discharge process

In the present study, cupric oxide (CuO) nanoparticles were synthesized by electrochemical discharge process using strong base electrolytes. The experiments were carried out separately using NaOH and KOH electrolytes. The mass output rate and the crystal size were obtained with variation of the rotation speed of magnetic stirrer for both types of electrolytes. The mass output rate of CuO nanoparticles increased with the increase in the speed of rotation, and, after an optimum speed, it started decreasing. However, the size of the particles reduced with the increase of the rotation speed. The crystal plane of the obtained CuO nanoparticles was similar for both the electrolytes whereas the yield of nanoparticles was higher in KOH as compared with NaOH under the same experiment conditions. In this set of experiments, the maximum output rates obtained were 21.66 mg h−1 for NaOH and 24.66 mg h−1 for KOH at 200 rpm for a single discharge arrangement. The average crystal size of CuO particles obtained was in the range of 13–18 nm for KOH electrolyte and 15–20 nm for NaOH electrolyte. Scanning electron microscopy images revealed that flower-like and caddice clew-shaped CuO nanocrystalline particles were synthesized by the electrochemical discharge process. Fourier transform infrared spectrum showed that the CuO nanoparticles have a pure and monolithic phase. UV–vis–NIR spectroscopy was used to monitor oxidation course of Cu → CuO and the band gap energy was measured as 2 and 2.6 eV for CuO nanoparticle synthesized in NaOH and KOH solutions, respectively.

Zn-doped SnO2 nano-urchin-enriched 3D carbonaceous framework for supercapacitor application

Hierarchical Zn-doped SnO2 nano-urchins decorated on RGO nanosheets were fabricated for supercapacitor applications. In this study, SnO2 nanospheres were doped with Zn2+ to tailor their electrical and morphological properties. Zn2+ doping of the SnO2 nanospheres prevented Sn clustering and thereby reduced the particle size leading to the formation of urchin-like nanostructures. These urchins with a high surface area and short transport paths can offer high capacitive performance by assembling with RGO nanosheets. The X-ray photoelectron spectroscopy and X-ray diffraction analyses confirmed the presence of SnO2 crystal planes and successful doping of the Zn2+. The incorporation of the RGO nanosheets augmented the coulombic efficiency, specific capacitance, and cycling performance. The enhancement of the capacitive behavior resulted from the synergistic effects owing to the combined properties of pseudocapacitance and double layer capacitance. The composite electrode material offered a specific capacitance of 635 F g−1 at a current density of 1 A g−1 and has a high cycling stability up to 5000 cycles with a capacitance retention of 78.4%.

Polyaniline-Stabilized Intertwined Network-like Ferrocene/Graphene Nanoarchitecture for Supercapacitor Application

The present work highlights the effective H-π interaction between metallocenes (ferrocene; Fc) and graphene and their stabilization in the presence of polyaniline (PANI) through π-π interactions. The PANI-stabilized Fc@graphene nanocomposite (FcGA) resembled an intertwined network-like morphology with high surface area and porosity, which could make it a potential candidate for energy-storage applications. The relative interactions between the components were assessed through theoretical (DFT) calculations. The specific capacitance calculated from galvanostatic charging/discharging indicated that the PANI-stabilized ternary nanocomposite exhibited a maximum specific capacitance of 960 F g- at an energy density of 85 Wh Kg-1 and a current density of 1 A g- . Furthermore, electrochemical impedance spectroscopy (EIS) analysis confirmed the low internal resistance of the as-prepared nanocomposites, which showed improved charge-transfer properties of graphene after incorporation of Fc and stabilization with PANI. Additionally, all electrodes were found to be stable up to 5000 cycles with a specific capacitance retention of 86 %, thus demonstrating the good reversibility and durability of the electrode material.

LCP Based Polymer Blend Nanocomposites

Reinforcement of thermoplastic polymer matrices with liquid crystalline polymers (LCP) has been studied extensively by different research groups. Results showed thermotropic LCP generally form in situ fibrils in a polymer matrix, under suitable conditions, which can reinforce the base matrix. To achieve the in-situ fibrillation, a draw force is required to deform the rigid LCP domains into fibrillar form. This draw force can be generated by the high viscous polymer matrix on the LCP domains during blending. But unfortunately most of the polymer blends are incompatible in nature which trigger the interfacial slippage at the polymer-LCP interface and hence trim down the drag force of base matrix upon LCP domains and restricts the LCP fibrillation. To counter this incompatibility, compatibilizers have been used to increase the interfacial adhesion and LCP fibrillation. However, compatibilizers for the polymers, processed at very high temperatures, needs to be highly thermal stable to sustain that processing temperature, without degradation. This problem can be solved by the use of nanoparticles, like carbon nanotube, which are highly thermal stable and due to their high aspect ratios, they can bind the two polymer phases together.