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Two dimensional metal chalcogenide-based sub-micron thin antenna for wireless communication
( Girish Gund ),박호석 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1
Smart wearable electronic demands thin and flexible radio-frequency (RF) antennas for wireless communication system. Previously, different nanostructured materials and metals have been used for RF antenna depends on their electrical conductivity. Metal-based antennas are thick and bulky due to their theoretical skin depth issue, which restrict miniaturized and portable electronics. Firstly, we report metallic two-dimensional (2D) metal chalcogenide-based monopole patch RF antenna, which is operated even at much lower thickness (sub-micron) than the skin depths of metals and omnidirectional RF propagation with reconfigurable resonance frequency. This work opens new approaches to design RF antennas for body-centric wearable communication systems.
( Girish Gund ),박호석 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1
The high potential and capacity of electroactive material is the stateof-the-art of energy storage technology. The scale up of these requirements with the low-cost and ecofriendly approach has become major topic of interest, which limits its commercialization. Accordingly current investigation efforts on the preparation of metal oxide directly on stainless steel substrate using simple Successive Ionic Layer Adsorption and Reaction method to achieve above mentioned demand. Furthermore, the performance enhancement has been achieved through defined nanostructure of electroactive material through controlling the preparative parameters of chemical methods. The performed electrochemical examination disclose the major influences on electrochemical features of metal oxide as consequences of distinct nanostructure growth through controlled parameters. This investigation provide key solutions and fundamental groundwork for energy storage application, which can be expand to other metal oxides.
High Frequency response Flexible Electrochemical Energy Storage Device for Pulse Energy Processing
( Girish Gund ),박호석 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
Todays, smart electronics intend towards designing of state-of-the-art of miniaturized, portable and self-powered multifunctional technology. But, desired performance and functionality from electrochemical energy storage devices to support such smart electronics are yet developing and restraining. Mainly, the energy storage and delivery rates are major challenge and appearing ahead of energy storage devices due to limitation of fast charge kinematics within the device. This limitations tend to work devices at only direct current, and quit functioning for pulse energy harvesting and current ripple filtering, which generally do conventional capacitors. In order to resolve this challenge, we fabricated ultrafast frequency response flexible electrochemical capacitors based on new conducting polymer/MXene hybrid electrodes and polymer gel electrolyte. The fabricated devices exhibited good electrochemical performance along with flexible functionality and ripple filtering capability.
Gund, Girish S.,Lokhande, Chandrakant D.,Park, Ho Seok Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.741 No.-
<P><B>Abstract</B></P> <P>The nickel-based oxides or hydroxides are considered a promising electroactive material for supercapacitor application owing to its low cost, well-defined redox activity, and prospect of controllable nanostructures. However, control of nanomorphology and uniform deposition onto a conductive substrate for Ni-based materials remains a critical challenge. Herein, we demonstrate the controlled synthesis of hierarchical nanoflake structure of NiO thin film by a simple and inexpensive successive ionic layer adsorption and reaction (SILAR) method and its consequent effect on supercapacitive performances. The as-prepared NiO thin films confirmed kinetically controlled growth model for the anisotropic nanostructure through a systematic investigation of controlling reaction temperatures and times. The as-optimized binder-free NiO thin film electrodes exhibited a reversible electrochemical feature, providing a high specific capacitance of 674 F g<SUP>−1</SUP> and cycling stability of 72.5% after 2000 cycles. These performances of NiO thin films were attributed to its open mesoporous and large accessible area of hierarchical nanoflakes structure, as well as the fast ion diffusion into the active sites. This work opens new avenues for the design of high capacity metal oxide thin films with hierarchical architecture for electrochemical energy storage applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hierarchical structure of NiO thin film was synthesized by SILAR. </LI> <LI> Synthetic parameters controlled the morphology of NiO thin films. </LI> <LI> Porous nanoflakes of NiO thin films was composed of fine nanoparticles. </LI> <LI> NiO thin films offered easy charge transportation and low ESR. </LI> <LI> NiO thin films showed high specific capacitance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Conducting Polymer based Hybrid networks for Ultrahigh Volumetric Multivalent ion Pseudocapacitance
( Girish Gund ),박호석 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
High volumetric energy density are demanding for space-limited applications. Supercapacitors have better cyclic and power capabilities compared to batteries, but restricted for low volumetric capacity due to low density of active materials (< 0.75 g/cc of AC) and intrinsic non-Faradaic charge storage process. To surplus these challenges, we first demonstrate ultrahigh volumetric capacitance of conducting polymer based hybrid material networks through the multivalent pseudocapacitance with significant durability. The electrochemistry of multivalent ion storage within the designed conducting polymer matrix was deeply investigated by in-situ ATR-FTIR spectroscopic analysis. Additionally, this unique electrochemistry was examined through in-situ 2D IR COS and PCA analyses. The obtained results inspire to design similar other new hybrid materials and put forth new avenue to design high volumetric capacitive materials for multivalent charge storage.
Binder-free approach to engineer hybrid supercapacitor
( Girish Gund ),박호석 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0
Nanostructured hybrid metal oxide@rGO electroactive material was directly coated on nickel-foam (NF) using two step binder-free and additive-less hydrothermal method. The material interface plays a vital role to control the dimensions of grown metal oxide nano-needle structure. The nano-needle dimensions in the case of bare NF are longer and thicker than rGO coated NF due to different surface energy. However, the smaller nano-needles grown on rGO coated NF reveals superior electrochemical performance like specific capacitance, coulombic efficiency, cycling stability, etc. compare to bare NF in alkaline 2 M KOH electrolyte due to improved interface resistances and adhesion. Whereas, rGO coated NF electrode demonstrate good capacitive response in negative potential window in the same alkaline electrolyte. So, the fabricated hybrid supercapacitor (HSC) reveals excellent electrochemical performance.
Facile synthesis of CNT branch grown steam activated-rGO for lithium sulfur battery cathode
백상하,박재민,( Girish Gund ),박호석 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1
Lithium-Sulfur battery has derived enormous interests from researchers with its high theoretical energy density (2600 Wh kg<sup>-1</sup>), nontoxicity, abundance of sulfur compared to traditional lithium ion battery. However, it has some problems that poor electric conductivities of sulfur and its compound, volume expansion during discharge stage, and irreversible capacity loss by dissolution of polysulfides called shuttle effect. In this research, we used microwave based CNT grown steam activated rGO for the conductivity issues and volume expansion problem, and metallocene, which is growth point of CNT, can act as confining agent for the polysulfide shuttling problem. 900 mAh g<sup>-1</sup> of initial capacity and 80 % capacity retention until 200<sup>th</sup> cycle were achieved at 0.1C.
Oh, Kyu Hyun,Gund, Girish Sambhaji,Park, Ho Seok The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.44
<P>We demonstrate nickel cobaltite@reduced graphene oxide (NiCo2O4@rGO) hybrid architectures directly deposited on nickel-foam (NF). The rGO interlayers restrict the growth of NiCo2O4 nanoneedles into smaller and thinner dimensions compared to NiCo2O4 without rGO layers, providing kinetic and structural stability for hybrid architectures. Accordingly, the NiCo2O4@rGO hybrid on NF achieves a specific capacitance of 1427 F g<SUP>−1</SUP> at 8 A g<SUP>−1</SUP>, a coulombic efficiency of 96.2%, and a capacitance retention of 83.8% over 10 000 cycles, which are greater than 1036 F g<SUP>−1</SUP>, 89.1%, and 40.8% of NiCo2O4 on NF in an aqueous 2 M KOH electrolyte. In order to enlarge the potential window of the aqueous system, hybrid supercapacitors (HSCs) are configured using the NiCo2O4@rGO hybrid on NF as a positive electrode and rGO on NF as a negative electrode. The HSCs exhibit a good cycling stability of 81.1% over 10 000 cycles, delivering maximum energy and power densities of 25.24 W h kg<SUP>−1</SUP> and 21.42 kW kg<SUP>−1</SUP>.</P>