Interconnected Pt-Nanodendrite/DNA/Reduced-Graphene-Oxide Hybrid Showing Remarkable Oxygen Reduction Activity and Stability

Tiwari, Jitendra N.,Kemp, Kingsley Christian,Nath, Krishna,Tiwari, Rajanish N.,Nam, Hong-Gil,Kim, Kwang S. American Chemical Society 2013 ACS NANO Vol.7 No.10

<P>Controlling the morphology and size of platinum nanodendrites (PtDs) is a key factor in improving their catalytic activity and stability. Here, we report the synthesis of PtDs on genomic-double-stranded-DNA/reduced-graphene-oxide (gdsDNA/rGO) by the NaBH<SUB>4</SUB> reduction of H<SUB>2</SUB>PtCl<SUB>6</SUB> in the presence of plant gdsDNA. Compared to industrially adopted catalysts (<I>i.e.</I>, state-of-the-art Pt/C catalyst, Pt/rGO, Pt<SUB>3</SUB>Co, <I>etc.</I>), the as-synthesized PtDs/gdsDNA/rGO hybrid displays very high oxygen reduction reaction (ORR) catalytic activities (much higher than the 2015 U.S. Department of Energy (DOE) target values), which are the rate-determining steps in electrochemical energy devices, in terms of onset-potential, half-wave potential, specific-activity, mass-activity, stability, and durability. Moreover, the hybrid exhibits a highly stable mass activity for the ORR over a wide pH range of 1–13. These exceptional properties would make the hybrid applicable in next-generation electrochemical energy devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2013/ancac3.2013.7.issue-10/nn4038404/production/images/medium/nn-2013-038404_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn4038404'>ACS Electronic Supporting Info</A></P>

Titanium Dioxide Nanomaterials and its Derivatives in the Remediation of Water: Past, Present and Future

Tiwari, Alka,Shukla, Alok,Tiwari, Diwakar,Choi, Suk Soon,Shin, Hyun-Gon,Lee, Seung-Mok The Korean Society of Industrial and Engineering C 2019 공업화학 Vol.30 No.3

The aim of this review article is to summarize the role of titanium oxide ($TiO_2$) nanomaterials in the remediation of the aquatic environment contaminated with various emerging pollutants. The advanced oxidation process led by the semiconductor $TiO_2$ is an impetus in the remediation technology. Therefore, a vast number of literature works are available in this area. Further, the role of modified $TiO_2$ or thin film materials were discussed in the review. Also, the Localized Surface Plasmon Resonance (LSPR) effect of using noble metaldoped $TiO_2$ played an interesting role in the remediation process.

Titanium Dioxide Nanomaterials and its Derivatives in the Remediation of Water: Past, Present and Future

( Alka Tiwari ),( Alok Shukla ),( Diwakar Tiwari ),( Suk Soon Choi ),( Hyun-gon Shin ),( Seung-mok Lee ) 한국공업화학회 2019 공업화학 Vol.30 No.3

The aim of this review article is to summarize the role of titanium oxide (TiO₂) nanomaterials in the remediation of the aquatic environment contaminated with various emerging pollutants. The advanced oxidation process led by the semiconductor TiO₂ is an impetus in the remediation technology. Therefore, a vast number of literature works are available in this area. Further, the role of modified TiO₂ or thin film materials were discussed in the review. Also, the Localized Surface Plasmon Resonance (LSPR) effect of using noble metaldoped TiO₂ played an interesting role in the remediation process.

Au-nanoparticle/nanopillars TiO2 meso-porous thin films in the degradation of tetracycline using UV-A light

Alka Tiwari,Alok Shukla,Lalliansanga,Diwakar Tiwari,이승목 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.69 No.-

Novel meso-porous nanoparticles Au/TiO2 thin films were obtained by template synthesis using polyethylene glycol as filler medium. The materials were characterized by advanced analytical methods. The photocatalysts were employed for the photocatalytic degradation of tetracycline from aqueous solutions using UV-A light (λmax 330 nm). Various physico-chemical parametric studies enabled to deduce the mechanism of degradation. A significant percentage of tetracycline was mineralized by the treatment. The stability of thin film was evidenced with the repeated use of thin film. The degradation of tetracycline was proceeded predominantly by the OH radicals generated at the valance and conduction band of semiconductor.

Impact of oil price risk on sectoral equity markets: Implications on portfolio management

Tiwari, Aviral Kumar,Jena, Sangram Keshari,Mitra, Amarnath,Yoon, Seong-Min Elsevier 2018 ENERGY ECONOMICS Vol.72 No.-

<P><B>Abstract</B></P> <P>Structure and degree of oil price impact on sectoral indices are examined using Quantile Regression Analysis (QRA). Nine sectors are found to provide diversification opportunities during a bull market (i.e. 90th quantile of the return distribution) and three sectors during a bear market (10th quantile) to hedge oil price risk. Further, the contagion effect and interdependency between oil price and sectoral equity are assessed through frequency domain causality. The causality from oil price in the long run determined that there is interdependence between three sectors and oil price changes. The direction of causality from oil price is mixed in both the short run (high frequency) and long run (low frequency) for nine sectors. Overall, the carbon sector is the only sector that is immune to oil price risk, thereby providing investment and hedging opportunities for portfolio managers.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Oil price shock impacts on Indian stock market sectoral index are investigated. </LI> <LI> We use asymmetric quantile regression and frequency-domain Granger causality. </LI> <LI> Oil price tail risk affects all sectoral indices other than of the carbon sector. </LI> <LI> A contagion effect for negative oil price shocks is found in six sectors. </LI> <LI> Interdependency is found in five sectors in the case of positive oil price shocks. </LI> </UL> </P>

Prevention of sulfur diffusion using MoS2-intercalated 3D-nanostructured graphite for high-performance lithium-ion batteries.

Tiwari, Anand P,Yoo, HeeJoun,Lee, JeongTaik,Kim, Doyoung,Park, Jong Hyeok,Lee, Hyoyoung RSC Pub 2015 Nanoscale Vol.7 No.28

<P>We report new three-dimensional (3D)-nanostructured MoS2-carbonaceous materials in which MoS2 sheets are intercalated between the graphite layers that possess a multiply repeated graphite/MoS2/graphite structure which prevents the aggregation of MoS2 and diffusion of sulfur from carbonaceous materials, enhancing the cycling stability of Li-ion batteries. We developed an efficient and scalable process applicable to mass production for synthesizing non-aggregated MoS2-intercalated 3D hybrid-nanostructured graphite based on stress induced and microwave irradiation. X-ray diffraction, X-ray photospectroscopy, Raman spectroscopy, field emission scanning electron microscopy, and high-resolution transmission electron microscopy analyses demonstrated that the as-synthesized materials consisted of MoS2-intercalated 3D hybrid-nanostructured graphite platelets that had a multiply repeated graphite/MoS2/graphite structure. The obtained MoS2-graphite powder surpasses MoS2 as an anode material in terms of specific capacity, cyclic stability, and rate performances at high current densities for Li-ion batteries. The electrochemical impedance spectroscopy demonstrated that the graphite sheets not only reduced the contact resistance in the electrode but also facilitated electron transfer in the lithiation/delithiation processes. The superior electrochemical performances especially for the cycling stability of the Li-ion battery originate from prevention of the sulfur diffusion of the MoS2-intercalated 3D-nanostructured graphite.</P>

A unified framework for operational range estimation of mobile robots operating on a single discharge to avoid complete immobilization

Tiwari, Kshitij,Xiao, Xuesu,Malik, Ashish,Chong, Nak Young Elsevier 2019 Mechatronics Vol.57 No.-

<P><B>Abstract</B></P> <P>Mobile robots are being increasingly deployed in fields where human intervention is deemed risky. However, in doing so, one of the prime concern is to prevent complete battery depletion which may in turn lead to immobilization of the robot during the mission. Thus, we need to carefully manage the energy available to explore as much of the unknown environment as feasible whilst guaranteeing a safe return journey to home base. For this, we need to identify the key components that draw energy and quantify their individual energy requirements. However, this problem is difficult due to the fact that most of the robots have different motion models, and the energy consumption usually also varies from mission to mission. It is desirable to have a generic framework that takes into account different locomotion models and possible mission profiles. This paper presents a methodology to unify the energy consumption models for various robotic platforms thereby allowing us to estimate operational range in both offline and online fashions. The existing models consider a given mission profile and try to estimate its energy requirements whilst our model considers the energy as a given resource constraint and tries to optimize the mission to be accomplished within these constraints. The proposed unified energy consumption framework is verified by field experiments for micro UGV and multi-rotor UAV test-beds operating under myriad of environmental conditions. The <I>online</I> model estimates operational range with an average accuracy (measured with respect to true range across multiple field trials) of 93.87% while the <I>offline</I> model attains 82.97%.</P>

Point-Wise Fusion of Distributed Gaussian Process Experts (FuDGE) Using a Fully Decentralized Robot Team Operating in Communication-Devoid Environment

Tiwari, Kshitij,Jeong, Sungmoon,Chong, Nak Young IEEE 2018 IEEE TRANSACTIONS ON ROBOTICS Vol.34 No.3

<P>In this paper, we focus on large-scale environment monitoring by utilizing a fully decentralized team of mobile robots. The robots utilize the resource constrained-decentralized active sensing scheme to select the most informative (uncertain) locations to observe while conserving allocated resources (battery, travel distance, <I>etc.</I>). We utilize a distributed Gaussian process (GP) framework to split the computational load over our fleet of robots. Since each robot is individually generating a model of the environment, there may be conflicting predictions for test locations. Thus, in this paper, we propose an algorithm for aggregating individual prediction models into a single globally consistent model that can be used to infer the overall spatial dynamics of the environment. To make a prediction at a previously unobserved location, we propose a novel gating network for a mixture-of-experts model wherein the weight of an expert is determined by the responsibility of the expert over the unvisited location. The benefit of posing our problem as a centralized fusion with a distributed GP computation approach is that the robots never communicate with each other, individually optimize their own GP models based on their respective observations, and off-load all their learnt models on the base station only at the end of their respective mission times. We demonstrate the effectiveness of our approach using publicly available datasets.</P>

Highly active and stable layered ternary transition metal chalcogenide for hydrogen evolution reaction

Tiwari, Anand P.,Kim, Doyoung,Kim, Yongshin,Prakash, Om,Lee, Hyoyoung Elsevier 2016 Nano energy Vol.28 No.-

<P><B>Abstract</B></P> <P>Layered ternary transition metal chalcogenides (TTMCs) material has great potentials that can overcome to the limitation of active sites which is challenging in binary transition metal chalcogenides (BTMC), such as MoS<SUB>2</SUB>, towards electrochemical hydrogen production. Here, we demonstrate TTMC material which contains two transition metals Cu and Mo with chalcogen S. The TTMC, Cu<SUB>2</SUB>MoS<SUB>4</SUB> has been successfully synthesized by a facile solution-processed method. Moreover, by anion doping such as Se in as the synthesized Cu<SUB>2</SUB>MoS<SUB>4</SUB>, it has been found that TTMC can be exfoliated into single layer nanosheets. Furthermore, by controlling the number of layers, single layers TTMC exhibit the highest electrocatalytic activity towards hydrogen evolution reaction (HER) because the single layers can provide more catalytic active sites than multilayers and bulk. The onset potential for hydrogen generation is −96mV for single layer TTMC electrode material with corresponding Tafel slope 52mV/decade. After 1000 cycles with continuous electrolysis in acid electrolyte for 15h, the electrode material preserves its structure and robust catalytic activity perfectly. Our new TTMC materials show highly active electrocatalytic performance and high stability which overcome the intrinsic limitation of BTMC. As a result, our work can guide new strategy for the developments of real applications of TMCs in HER.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Single layered ternary transition metal chalcogenides have been synthesized for highly active and stable electrocatalyst. </LI> <LI> Se-doping plays an essential role to exfoliate Cu<SUB>2</SUB>Mo(S<SUB>1-y</SUB>Se<SUB>y</SUB>)<SUB>4</SUB> for high electrochemical active surface. </LI> <LI> Se-doping strategy can be implemented to exfoliate and enhance electrocatalytic activity of transition metals chalcogens. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Effective approaches to synthesis of single layered ternary transition metal chalcogenide (TTMC) have been developed to produce highly active and stable electrocatalyst towards hydrogen evolution reaction. The single layered TTMC are achieved by Se-doping in Cu<SUB>2</SUB>MoS<SUB>4</SUB> which can be applicable for other transition metal chalcogenide (TMC).</P> <P>[DISPLAY OMISSION]</P>

Chemical strain formation through anion substitution in Cu₂WS₄ for efficient electrocatalysis of water dissociation

Tiwari, Anand P.,Azam, Ashraful,Novak, Travis G.,Prakash, Om,Jeon, Seokwoo The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.17

<P>Researchers have revealed that the electrocatalytic activity can be improved by creation of defects in the crystal lattice of 2D layered transition metal dichalcogenides (TMDCs) or ternary metal chalcogenides (TMCs) such as MoS2 or Cu2MoS4, respectively. However, the role of anion substitution in the enhancement of overall electrocatalytic activity in TMCs remains unproven. Here, we show the substitution of anion atom sulfur (S) with selenium (Se) in a new electrocatalyst Cu2WS4 for efficient hydrogen evolution reaction (HER) activity. The higher electrocatalytic activity of Cu2WS4 after anion atom substitution can be attributed to the creation of chemical strain in the lattice, which causes an increase of active sites for hydrogen adsorption and desorption. Experimentally, the anion substituted Cu2W(SySe1 − y)4 samples show superior electrocatalytic activities with a low onset potential of −0.320 V at 10 mA cm<SUP>−2</SUP> for the HER, which is two-fold lower than that of the pristine Cu2WS4 (−0.650 V at 10 mA cm<SUP>−2</SUP>) sample. In addition, after 1000 cycles with continuous electrolysis in an acid electrolyte for 12 h, the anion substituted samples Cu2W(SySe1 − y)4 preserve their structure and robust catalytic activity perfectly. As a result, our work demonstrates a new approach for developments of real applications of TMCs in energy conversion.</P>