Manikantan Kota - Academia.edu (original) (raw)

Papers by Manikantan Kota

Journal of Power Sources, 2016

Abstract The three-dimensional (3D), nitrogen doped reduced graphene oxide (N-RGO) monoliths have... more Abstract The three-dimensional (3D), nitrogen doped reduced graphene oxide (N-RGO) monoliths have been synthesized using graphene oxide and melamine through an ice-templated assembly. The self-assembled monoliths are accompanied with the considerable reduction of graphene oxide after annealing and specific surface area of 190 m 2 g −1 . The blue shift of approximately 22 cm −1 and 4 cm −1 in D and G bands for N-RGO is notified in Raman analysis, confirming the incorporation of nitrogen onto the graphene sheet. In addition, an extra peak at 1251 cm −1 appears possibly due to the stretching vibration of C–N bonds. The detailed doping configurations analyzed by x-ray photoemission spectroscopy indicate the nitrogen content of around 6.2 at% in the N-RGO with predominant pyridinic N-type configuration. The specific capacitance is enhanced up to 217 F g −1 at a scan rate of 5 mV s −1 , which is approximately three times higher than that of the pristine 3D RGO owing to the pseudocapacitive behavior of N-RGO. The high electronic conductivity of the N-RGO electrode with low charge transfer resistance as confirmed by electrochemical impedance spectroscopy is associated with good rate capability. Furthermore, the N-RGO sample exhibits an excellent cyclic stability with no decay in capacitance even after 5000 cycles at scan rate of 100 mV s −1 .

Energy Storage Materials, May 1, 2019

Achieving both performances and functionalities of energy storage devices at extreme conditions r... more Achieving both performances and functionalities of energy storage devices at extreme conditions remains a critical challenge due to the property trade-offs of materials. Here, we demonstrate highly ion-conducting, stretchable, and ultradurable double network (DN) ionogel films, where ionic liquids are confined in chemically-coupled DNs consisting of hard and soft polymers, for high-temperature flexible supercapacitors (hfSCs). Both mechanical and electrochemical integrities at high temperatures are attributed to the unique DN structure and thermally activated ionic transport of the ionogels. Even at 100°C, the DN ionogel film demonstrates remarkable properties, such as the ionic conductivity of 36.8 mS cm −1 , the tensile strength of 1.4 MPa, stretchability of 500%, and dissipation energy of 216 kJ m −3. Thus, the hfSCs achieve the highest energy density of 51.0 Wh kg −1 at 180°C among previous solid-state SCs, showing extreme durability of 91% over 100,000 cycles and functional hybrid system at both elevated temperatures and bent states.

Nucleation and Atmospheric Aerosols, 2013

ABSTRACT Few-walled carbon nanotubes (CNTs) were synthesized by the arc discharge process. The st... more ABSTRACT Few-walled carbon nanotubes (CNTs) were synthesized by the arc discharge process. The study pertains to analyze the effect of buffer gas pressure (Helium) and density of graphite anodes on morphology and yield of CNTs. The synthesis of CNTs was carried out at different buffer pressures of Helium ranging from 80 Torr to 600 Torr using different anode densities specifically 1.6 and 1.8 gm/cc. FE-SEM and TGA studies indicated that the highest percentage of MWCNTs was formed around 450 Torr pressure as compared to other pressures. It was observed that the variation of gas pressure affects the current drawn capacity and also the evaporation rate of the graphite electrode. Micro-structure of CNTs synthesized at 450 Torr consists of 8 concentric graphene layers. Improved crystallinity with better thermal stability was observed in case of high density graphite anode.

Advanced Materials, Aug 1, 2019

Macromolecular Research, Oct 1, 2017

The nitrogen (N)-doped reduced graphene aerogel (NRGA) with high Ndoping level is successfully fa... more The nitrogen (N)-doped reduced graphene aerogel (NRGA) with high Ndoping level is successfully fabricated via chemical converted method and thermal activation. N-atoms can be incorporated at a high temperature of 900 o C and distort the lattice structure of RGA by the formation of different N-configuration bindings. NRGA exhibits a larger surface area than GA, and the surface morphology is roughened as characterized by microscopic analysis. As confirmed by X-ray photoelectron spectroscopy (XPS) result, the pyridinic-and/or pyrrolic-N bindings modified electronic structures to improve the electrochemical properties. The specific capacitance of NRGA is increased to 289 F g-1 at 10 mV s-1 with rate capability of 75% and cyclic stability of 86%. These excellent electrochemical performances of NRGA are due to the synergistic structure effect which provide a large accessible area and rapid ion transfer pathways, as well as N-containing groups acting as the electrochemical active sites positioned at the edge or on-plane of NRGA lattices.

Journal of Alloys and Compounds, Apr 1, 2019

We demonstrate a facile hydrothermal synthesis of the interconnected porous NiCo 2 O 4 nanosheets... more We demonstrate a facile hydrothermal synthesis of the interconnected porous NiCo 2 O 4 nanosheets for hybrid supercapacitor applications. The as-synthesized NiCo 2 O 4 nanosheets show a high specific capacitance of 3137 F g −1 at a current density of 2 A g −1 , which is much greater than 1916 and 1251 F g −1 of Co 3 O 4 and NiO, respectively. Interestingly, the total specific capacitance of the NiCo 2 O 4 is almost close to the sum of the specific capacitance of the NiO and Co 3 O 4. Furthermore, a hybrid supercapacitor is configured with the NiCo 2 O 4 nanosheets and the nitrogen-and sulfur-codoped reduced graphene oxide as the positive and negative electrodes, respectively. This hybrid supercapacitor delivers a maximum energy density of 33.64 W h kg −1 at a power density of 1,196 W kg −1 and excellent long-term cyclic stability over 12,000 charge/discharge cycles at the enlarged voltage window of 1.5 V. The remarkable supercapacitive performances of the hybrid device are attributed to the interconnected porous structure of NiCo 2 O 4 nanosheets and three-dimensional continuous macropores of codoped reduced graphene oxides.

Journal of Power Sources, Sep 1, 2018

The 3D hieratically porous doped graphene architecture is constructed. • Heteroatoms are uniforml... more The 3D hieratically porous doped graphene architecture is constructed. • Heteroatoms are uniformly distributed onto the 3D graphene surface. • A full cell supercapacitor is fabricated using organic electrolytes. • Energy density of cell is enhanced improving specific capacitance and potential window.

Ceramics International, 2018

The integration of pseudocapacitive metal oxides with reduced graphene oxide (RGO) is considered ... more The integration of pseudocapacitive metal oxides with reduced graphene oxide (RGO) is considered an innovative chemical strategy to resolve both bottlenecks of pseudocapacitor and electrical double-layer capacitor for high performance supercapacitors. Herein, we report a facile synthesis method of highly porous three-dimensional (3D) CoO/RGO nanocomposite via ozone treatment, ice templating, and thermal annealing. The ozonized RGO surface provides a favorable interaction with cobalt precursor for a stable and uniform deposition of well-defined CoO nanoparticles. The morphology, structure, and chemistry of the resulting CoO/RGO nanocomposites are comprehensively characterized by spectroscopic methods. The CoO/RGO nanocomposites show fast and reversible pseudocapacitance due to a large accessible area, rapid ion transport, and low charge transfer resistance arising from 3D internetworked macroporosity. Thus, the nanocomposites achieve high specific capacitance up to 239.4 F g-1 (volumetric capacitance = 12.04 F cm-3), excellent rate capability of 79.1%, and ultralong cyclic stabilities (of 93.2% at 10 A g-1 even up to 10,000 cycles) in 6 M KOH electrolyte. This simple synthesis method offers a promising solution for the design of high performance hybrid energy storage materials consisting of high capacity metal oxides and conductive graphene networks.

Journal of Power Sources, May 1, 2019

Crystalline phases and interlayer distance of Co(OH) 2 are controlled. • αand β-Co(OH) 2 reveal f... more Crystalline phases and interlayer distance of Co(OH) 2 are controlled. • αand β-Co(OH) 2 reveal flake-like and nanorod-like structures. • β-Co(OH) 2 shows 1066 F g −1 at 2 A g −1. • β-Co(OH) 2 reveals 80% of its initial capacitance at 20 A g −1. • Asymmetric supercapacitor achieves 20.05 W h kg −1 and 10,000 cycle stability.

Advanced Materials, Apr 23, 2019

and Technology. His research focuses on designing carbon materials for electrochemical applicatio... more and Technology. His research focuses on designing carbon materials for electrochemical applications such as fuel cells, capacitive deionization, supercapacitors, and batteries.

Joule, 2019

Energy storage devices are limited by the trade-off between the transport properties and charge s... more Energy storage devices are limited by the trade-off between the transport properties and charge storage ability of materials. Electrolytic capacitors are kinetically fast, operating at kHz frequency, but limited by low capacitance. Electrochemical capacitors (ECs) provide high capacitance, yet their sluggish kinetics limit frequency response. Herein, we devise porous MXene/conducting polymer hybrids for large-scale flexible AC filtering symmetric ECs. These MXene hybrid-based ECs bridge the performance gap between high capacitance and frequency response, toward the form-factor-free miniature and scalable devices.

Journal of Alloys and Compounds, Dec 1, 2017

Carbon nanotubes branched on threedimensional, nitrogen-incorporated reduced graphene oxide/iron ... more Carbon nanotubes branched on threedimensional, nitrogen-incorporated reduced graphene oxide/iron oxide hybrid architectures for lithium ion battery anode,

Ceramics International, Feb 1, 2018

Graphene is considered a promising active electrode material due to a large surface area, high el... more Graphene is considered a promising active electrode material due to a large surface area, high electronic conductivity, and chemical and mechanical stabilities for supercapacitor (SC) applications. However, the current bottleneck is the fabrication of restacking-inhibited graphene on an electrode level which otherwise loses the capability to achieve the aforementioned properties. Herein, we demonstrate the synthesis of restacking-inhibited nitrogen (N)-incorporated mesoporous graphene for high energy SCs. The melamine-formaldehyde acts as a restacking inhibitor by forming a bonding with reduced graphene oxide (RGO) through a condensation reaction and as an N precursor to be decomposed to create open pores and N sources upon heat treatment. The dspacing increases up to 0.352 nm and the surface area is as high as 698 m 2 g −1 with high mesoporosity, confirming restacking inhibition by N incorporation decomposed by melamine-formaldehyde. The restacking-inhibited RGO-based SC cells in organic electrolyte show the specific capacitance of 25.8 F g −1 , the energy density of 21.8 kW kg −1 and 85% of capacitance retention for 5000 cycles, which are better than those of pristine RGObased cells. These improved SC performances are attributed to the fast ion transport through a mesoporous channel in crumpled structure and the doping effect of N incorporation. This work provides a simple yet effective chemical approach to fabricate restacking-inhibited RGO electrodes for improved SC performances.

Advanced Energy Materials, May 2, 2017

sluggish solid-state ion diffusion along the principal axis perpendicular to the basal plane, whi... more sluggish solid-state ion diffusion along the principal axis perpendicular to the basal plane, which makes LIBs inapplicable for high energy and power-demanding applications. [5] In order to overcome the low capacity of graphite, various transition metal oxides have been investigated due to their higher theoretical capacities, achieved via a conversion mechanism. However, the practical application of transition metal oxides in high energy LIBs is hindered by the poor cycling stability and rate capability of these oxides, which are respectively associated with the large volume changes that occur during the charge/discharge cycling and the low electronic conductivity. [6] Various carbonaceous materials, such as carbon nanotubes (CNTs), graphenes, porous carbon, hollow nanospheres, carbon capsules, graphene nanoribbons, and graphene nanosheets, have been used to resolve the aforementioned problems in the form of nanocomposites or hybrids due to their large surface area and extraordinary electronic and mechanical properties. [7-12] In particular, numerous approaches have been made to develop CNT/ metal oxide composites; [7] however, satisfactory performance has not yet been achieved. This is mainly due to the aggregation and bundling of the CNTs, arising from strong van der Waals and π-π interactions, which leads to loss of the available surface area and higher Li + ion diffusion resistance. The synergistic combination of a 3D architecture with heterocomposition may provide a large accessible area, alleviate the volume expansion, and create short solid-state diffusion pathways, resulting in the enhanced rate and cyclic capabilities. [13] Nonetheless, the strong attachment of the active materials onto the carbon supports and the proximate contact need to be achieved to exploit the synergistic advantages of both components. [14] Biomimetic design inspired by nature's structures and functions is of prime importance for resolving the existing technological challenges. Such biomimetic approaches have been employed to resolve issues related to the performances of energy storage devices and materials, which are otherwise difficult to overcome with conventional artificial methodologies. For instance, Liu and co-workers mimicked the structural design of the Gecko's foot to improve the adhesion between a copperbased current collector and graphitic anode material, thereby achieving a dramatic increase of the LIB lifespan. [15] Moreover, It is crucial to control the structure and composition of composite anode materials to enhance the cell performance of such anode materials for lithium ion batteries. Herein, a biomimetic strategy is demonstrated for the design of high performance anode materials, inspired by the structural characteristics and working principles of sticky spider-webs. Hierarchically porous, sticky, spider-web-like multiwall carbon nanotube (MWCNT) networks are prepared through a process involving ozonation, ice-templating assembly, and thermal treatment, thereby integrating the networks with γ-Fe 2 O 3 particles. The spider-web-like MWCNT/γ-Fe 2 O 3 composite network not only traps the active γ-Fe 2 O 3 materials tightly but also provides fast charge transport through the 3D internetworked pathways and the mechanical integrity. Consequently, the composite web shows a high capacity of ≈822 mA h g −1 at 0.05 A g −1 , fast rate capability with ≈72.3% retention at rates from 0.05 to 1 A g −1 , and excellent cycling stability of >88% capacity retention after 310 cycles with a Coulombic efficiency >99%. These remarkable electrochemical performances are attributed to the complementarity of the 3D spider-web-like structure with the strong attachment of γ-Fe 2 O 3 particles on the sticky surface. This synthetic strategy offers an environmentally safe, simple, and cost-effective avenue for the biomimetic design of high performance energy storage materials.

ACS energy letters, Dec 28, 2020

Despite the clear benefits of Na and S active materials, Na–S hybrid energy storage devices have ... more Despite the clear benefits of Na and S active materials, Na–S hybrid energy storage devices have yet to be exploited, and existing Na–S batteries cannot provide fast kinetics and long-term stabilit...

Journal of Power Sources, Oct 1, 2018

• Nanohorn-like Co 3 O 4 architectures are synthesized. • The high specific capacitance of 2751 F... more • Nanohorn-like Co 3 O 4 architectures are synthesized. • The high specific capacitance of 2751 F g −1 is obtained at the optimized temperature. • Energy density of hybrid supercapacitor is ∼31.70 W h kg −1. • Capacitance retention is 91.37% over 350,000 charge-discharge cycles.

Advanced Energy Materials, Sep 1, 2017

Enhancement of heat transfer coefficient continues to be an important research area in various fi... more Enhancement of heat transfer coefficient continues to be an important research area in various fields of engineering ranging from microelectronics to high powered automobiles. The initial effort in the present research study is to enhance the heat transfer coefficient in a vehicle radiator using nanofluids with high thermal conductivity. The world's most abundant element 'Carbon' astoundingly exists in various structures and one such form is tube commonly known as Carbon Nanotubes (CNTs). Heat transfer enhancement in water and coolant based systems with different concentrations of nano particles (carbon nanotubes) have been investigated from an engineering system perspective. One such system considered is a "SUZUKI (800CC)-CAR RADIATOR", cooling circuit using different nanofluids to replace the conventional engine coolant. In the present study, the effect of nano-fluid heat transfer to enhance in water and coolant based systems with multi walled carbon nanotubes has been investigated. The improvement of heat transfer when compared to water, coolant (water + ethylene glycol 60:40) and water with MWCNTS and coolant with MWCNTS has been studied. It has been observed that there is an enhancement of heat transfer up to 30% when coolant and CNTS are used as a cooling medium.

Batteries

Conventional boron nitride material is a resistant refractory compound of boron and nitrogen with... more Conventional boron nitride material is a resistant refractory compound of boron and nitrogen with various crystalline forms. The hexagonal form, which corresponds to graphite, is used as a lubricant and an additive to cosmetic products because of its higher stability and softness. Recently, various nanostructured boron nitride materials, including nanosheets, nanotubes, nanoparticles, and nanocomposites with diverse new properties, have been achieved through the development of advanced synthesis techniques as well as a deeper understanding of the properties and related applications. As nanostructured boron nitride materials exhibit high chemical, thermal and mechanical stability, the incorporation of nanostructured boron nitride materials into the key components (electrolytes, separators, and electrodes) of electrochemical systems can alleviate various inherent problems. This review article systematically summarizes the integration of nanostructured boron nitride into electrolytes, ...

ACS Energy Letters, 2020