Electrochemically growth-controlled honeycomb-like NiMoO₄ nanoporous network on nickel foam and its applications in all-solid-state asymmetric supercapacitors

Kumbhar, Vijay S.,Nguyen, Van Quang,Lee, Yong Rok,Lokhande, Chandrakant D.,Kim, Do-Heyoung,Shim, Jae-Jin The Royal Society of Chemistry 2018 NEW JOURNAL OF CHEMISTRY Vol.42 No.18

<P>A honeycomb-like NiMoO4 nanoporous network electrode was synthesized on nickel foam using an electrodeposition method and used for the fabrication of asymmetric supercapacitors (ASCs). The growth process of the NiMoO4 nanostructure was controlled by varying the number of electrochemical cycles. The evolution of the NiMoO4 nanoflakes with the electrochemical cycles was confirmed by field emission scanning electron microscopy. The supercapacitive properties of NiMoO4 nanostructure were measured by cyclic voltammetry, galvanostatic charge discharge, and electrochemical impedance spectroscopy. The well-grown NiMoO4 nanoporous network exhibited a highest specific capacitance of 1475 F g<SUP>−1</SUP> at a current density of 1 A g<SUP>−1</SUP> in an aqueous KOH electrolyte with a good rate capability of 72.8% when the current density was increased 20 fold. The nanoporous network also exhibited a capacitive retention of 87.9% after 5000 charge-discharge cycles at a fixed current density of 20 A g<SUP>−1</SUP>. A NiMoO4//reduced graphene oxide (rGO)-based solid state ASC was fabricated using a poly(vinyl alcohol)-KOH gel electrolyte. The NiMoO4//rGO ASC delivered a maximum energy density of 45 W h kg<SUP>−1</SUP> and a power density of 14.5 kW kg<SUP>−1</SUP> as well as an electrochemical stability of 84% after 5000 cycles, highlighting the potential of NiMoO4//rGO ASCs for portable electronic applications.</P>

Interfacial growth of the optimal BiVO₄ nanoparticles onto self-assembled WO₃ nanoplates for efficient photoelectrochemical water splitting

Kumbhar, Vijay S.,Lee, Hyeonkwon,Lee, Jaewon,Lee, Kiyoung Elsevier 2019 JOURNAL OF COLLOID AND INTERFACE SCIENCE - Vol.557 No.-

<P><B>Abstract</B></P> <P>Photoelectrochemical water splitting is the most efficient green engineering approach to convert the sun light into hydrogen energy. The formation of high surface area core-shell heterojunction with enhanced light-harvesting efficiency, elevated charge separation, and transport are key parameters in achieving the ideal water splitting performance of the photoanode. Herein, we demonstrate a first green engineering interfacial growth of the BiVO<SUB>4</SUB> nanoparticles onto self-assembled WO<SUB>3</SUB> nanoplates forming WO<SUB>3</SUB>/BiVO<SUB>4</SUB> core-shell heterojunction for efficient PEC water splitting performance. The three different WO<SUB>3</SUB> nanostructures (nanoplates, nanobricks, and stacked nanosheets) were self-assembled on fluorine doped tin oxide glass substrates via hydrothermal route at various pH (0.8–1.2) of the solutions. In comparison to nanobricks and stacked nanosheets, WO<SUB>3</SUB> nanoplates displayed considerably elevated photocurrent density. Moreover, a simple and low cost green approach of modified chemical bath deposition technique was established for the optimal decoration of a BiVO<SUB>4</SUB> nanoparticles on vertically aligned WO<SUB>3</SUB> nanoplates. The boosted photoelectrochemical current density of 1.7 mA cm<SUP>−2</SUP> at 1.23 V vs. reversible hydrogen electrode (RHE) under AM 1.5 G illumination was achieved for the WO<SUB>3</SUB>/BiVO<SUB>4</SUB> heterojunction which can be attributed to a suitable band alignment for the efficient charge transfer from BiVO<SUB>4</SUB> to WO<SUB>3</SUB>, increased light harvesting capability of outer BiVO<SUB>4</SUB> layer, and high charge transfer efficiency of WO<SUB>3</SUB> nanoplates.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Social C-RAN: Novel Futuristic Paradigm for Next-Generation Cellular Networks

Kumbhar, Farooque Hassan,Singh, Sukhdeep,Saxena, Navrati,Roy, Abhishek Informa UK (TaylorFrancis) 2018 IETE technical review Vol.35 No.3

<P>Progressive growth of smartphones and number of users in the network demands for increase in network capacity. Proliferation in network capacity in turn triggers the problems like increase in Capital and Operational Expenditures (CAPEX/OPEX), decrease in Quality of Services (QoS), inflation in power consumption and the like. To cater the aforementioned network challenges, Cloud Radio Access Network (C-RAN) is introduced with the capability of centralization, virtualization and co-ordination. The commercialization of C-RAN further faces problems like dynamic resource allocation environment, co-operative transmission and reception techniques, interconnection and management of base band unit (BBU) instances in a BBU pool, etc. Therefore, the social paradigm when blended with C-RAN, the evolved C-RAN, i.e. Social C-RAN, promises to overcome the challenges of C-RAN. We contribute a fresh novel proposal of Social C-RAN in which network elements will be connected with the help of social relationships and properties they exhibit. Our quantitative results show that the vision of social layer introduced in the C-RAN architecture automates several functions like handover, frequency assignment, dynamic resource allocation and results in reducing communication delays in various applications. We select the potential applications that play a major role in evolving cellular networks and discuss the possibilities to optimize these applications further using our proposed Social C-RAN architecture.</P>

Electrosynthesis of a corn flake-like NiO nanostructure on nickel foam for polymer gel electrolyte-based high performance asymmetric supercapacitors

Kumbhar, V.,Cho, M.,Lee, J.,Kim, W.,Lee, M.,Lee, Y.,Shim, J. J. Royal Society of Chemistry 2017 NEW JOURNAL OF CHEMISTRY Vol.41 No.19

Hierarchical coating of MnO₂ nanosheets on ZnCo₂O₄ nanoflakes for enhanced electrochemical performance of asymmetric supercapacitors

Kumbhar, Vijay S.,Kim, Do-Heyoung Elsevier 2018 ELECTROCHIMICA ACTA Vol.271 No.-

<P><B>Abstract</B></P> <P>The design of heterostructured pseudo-capacitive materials plays a key role in fabricating asymmetric supercapacitors (ASCs) with high energy density and electrochemical cycle life for the evolution of next-generation energy storage devices. Use of ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanoflakes covered with MnO<SUB>2</SUB> nanosheets led to a synergistic effect that produced a larger electroactive surface area for charge storage than that provided by bare ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanoflakes or MnO<SUB>2</SUB> nanosheets. The ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanoflakes served as the backbone for the growth of the MnO<SUB>2</SUB> nanosheets. The ZnCo<SUB>2</SUB>O<SUB>4</SUB>-MnO<SUB>2</SUB> heterostructure was synthesized on Ni foam using a combined binder-free electrodeposition and hydrothermal method. The electrode formed using this unique method showed a maximum specific capacitance of 2057 F g<SUP>−1</SUP> at a current density of 1 A g<SUP>−1</SUP> with a rate capability of 65% even after a 15-fold increase in current density. Moreover, the electrode showed a cycling stability of 96.5% after 5000 successive cycles at a current density of 15 A g<SUP>−1</SUP>. An ASC formed using ZnCo<SUB>2</SUB>O<SUB>4</SUB>-MnO<SUB>2</SUB> as the positive electrode and activated carbon as the negative electrode delivered a maximum energy density of 69 W h kg<SUP>-1</SUP> with 93.5% capacity retention after 5000 cycles. Further, an experiment to investigate the commercial application of ASCs was conducted.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A MnO<SUB>2</SUB> nanosheets were coated on ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanoflakes using a simple, eco-friendly, and low cost chemical methods. </LI> <LI> The ZnCo<SUB>2</SUB>O<SUB>4</SUB>-MnO<SUB>2</SUB> heterostructure exhibited a specific capacitance of 2057 F g<SUP>-1</SUP>. </LI> <LI> The ZnCo<SUB>2</SUB>O<SUB>4</SUB>-MnO<SUB>2</SUB> heterostructure exhibited a cycling stability of 96.5% after 5000 cycles. </LI> <LI> As-fabricated ZnCo<SUB>2</SUB>O<SUB>4</SUB>//activated carbon asymmetric supercapacitor (ASC) exhibited an energy density of 69 W h kg<SUP>-1</SUP>. </LI> <LI> Finally the demonstration of the as-prepared ASC confirmed the practical feasibility of the device. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Reliable Relay: Autonomous Social D2D Paradigm for 5G LoS Communications

Kumbhar, Farooque Hassan,Saxena, Navrati,Roy, Abhishek IEEE 2017 IEEE communications letters Vol.21 No.7

<P>Next generation 5G networks contemplate to exploit millimeter Wave (mmWave) for a massive increase in data rates but its inherent characteristic of line-of-sight (LoS) brings up the challenge of directional synchronization of transmitters and receivers. In this letter, we propose a fusion of social Internet-of-Things and device-to-device (D2D) communications, shaping social D2D to tackle mmWave LoS challenge using an independent “reliable relay” scheme. We introduce distributed social network of devices and propose social-communication graph formation and autonomous trustworthy relay procedure. Utilizing reliable relay, a non-LoS device can communicate to 5G networks without compromising the contents privacy. Our analysis demonstrates that agile reliable relay substantially improves the capacity gain and data rate and can be an integral part of existing relay selection schemes. NS3-based simulations validate the proliferation in throughput with minimum additional delays.</P>

Performance assessment of RC frame designed using force, displacement & energy based approach

Onkar G. Kumbhar,Ratnesh Kumar 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.73 No.6

Force based design (FBD) approach is prevalent in most of the national seismic design codes world over. Direct displacement based design (DDBD) and energy based design (EBD) approaches are relatively new methods of seismic design which claims to be more rational and predictive than the FBD. These three design approaches are conceptually distinct and imparts different strength, stiffness and ductility property to structural members for same plan configuration. In present study behavioural assessment of frame of six storey RC building designed using FBD, DDBD and EBD approaches has been performed. Lateral storey forces distribution, reinforcement design and results of nonlinear performance using static and dynamic methods have been compared. For the three approaches, considerable difference in lateral storey forces distribution and reinforcement design has been observed. Nonlinear pushover analysis and time history analysis results show that in FBD frame plastic deformation is concentrated in the lower storey, in EBD frame large plastic deformation is concentrated in the middle storeys though the inelastic hinges are well distributed over the height and, in DDBD frame plastic deformation is approximately uniform over the height. Overall the six storey frame designed using DDBD approach seems to be more rational than the other two methods.

Fabrication of ultra-small NiMoO₄ nanoparticles deposited NiCo₂O₄ nanoflakes core-shell array for supercapacitors

Vijay S. Kumbhar,이기영 한국표면공학회 2019 한국표면공학회 학술발표회 초록집 Vol.2019 No.5

Hydrothermal Synthesis of Orthorhombic MoO3 Nanoblades: Electrochemical Characterization for Enhanced Supercapacitor Performance

Aditi A. Kumbhar,Kim Chihoon,Vaibhav C. Lokhande,Seung-Ho Ohk,Taeksoo jia 대한전자공학회 2024 대한전자공학회 학술대회 Vol.2024 No.6

Orthorhombic MoO₃ was synthesized by a simple, low cost and scalable hydrothermal method. With acidification of (NH₄)₂MoO₄) ammonium molybdate. The structural and morphological characteristics were carried out by using X-ray diffraction (XRD), field emission microscopy (FESEM), and Fourier transform infrared (FTIR) respectively. Nanoblades like morphology was observed by FESEM images at different magnifications. The electrochemical properties of the material were carried out in 1M H₂SO₄ as an electrolyte. The MoO₃ ensures good cyclic voltammetry behavior with a maximum specific capacitance of 22.85 Fg<SUP>-1</SUP> at 5 mVs<SUP>-1</SUP>. The energy density and power density of 5.55 Whkg<SUP>-1</SUP> and 17.85 Wkg<SUP>-1</SUP> respectively are calculated from the GCD study. An electrochemical impedance study was also conducted in 1M H₂SO₄ electrolyte.

On-demand High Mobility Vehicular Connectivity Prediction using Random Forest Classification

Farooque Hassan Kumbhar,Soo Young Shin 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.6

Innovations and advances in the communication technologies for vehicular networks enable high data rates and efficient network access. However, the stochastic nature of high mobility vehicular networks creates challenges in ad-hoc communication and efficient route selection. We believe that pro-actively identifying the connectivity between two communicating devices can help in efficient route selection for higher successful message delivery. In this paper, we design a comprehensive dataset using OpenStreetMap and SUMO traffic trace to evaluate three major machine learning techniques on high mobility vehicles. Our results identified that the random forest classification method outperforms logistic regression and support vector machine in terms of accuracy and F1-score metrics.