Kumar Sidhartha K Varadwaj

He holds the position of Reader at Department of Chemistry. He has more than 10 years of teaching and research experience in the extended field of materials chemistry. He has 25 publications in peer review journals to his credit. He completed Ph.D. on 2007 from IIT Kharagpur. The thesis work was based on studies of superparamagnetic particles. His postdoctoral work at KAIST, South Korea consisted of vapor phase deposition of silicide nanowires, their ensemble magnetic property and single nanowire magnetoresistance. He further moved to Research centre for integrated quantum electronics (RCIQE) at Hokkaido University, Japan where he worked on semiconductor nanowire growth on patterned structure and single nanowire lasers. He has special interest in popularisation of science through community outreach programs. His current research interest is focused on designing heterostructure materials for energy related electrocatalytic processes. Understanding the descriptors that control the activity of the catalysts. Development of electrochemical biosensors.

Selected Publications

  1. B. D. Mohapatra, I. Hota, S. P. Mantry, N. Behera, P. Parhi and K. S. K. Varadwaj, Understanding the oxygen evolution activity trend in Co2FeLDH-N doped graphene hybrids, Electrochem. Sci. Adv. 2020, doi:10.1002/elsa.202000009.
  2. S. P. Mantry, B. D. Mohapatra, N. Behera, P. Mishra, P. Parhi and K. S. K. Varadwaj, Potentiostatic Regeneration of oxygen reduction activity in MnOx@ Graphene hybrid nanostructures, Electrochimica Acta, 2019, 325, 134947.
  3. N. Behera, S. P. Mantry, B. D. Mohapatra, R. K. Behera and K. S. K. Varadwaj, Functional molecule guided evolution of MnOx nanostructure patterns on N-graphene and their oxygen reduction activity, RSC Advances, 2019, 9, 27945–27952.
  4. B. D. Mohapatra, S. P. Mantry, N. Behera, B. Behera, S. Rath and K. S. K. Varadwaj, Stimulation of Electrocatalytic Oxygen Reduction Activity on Nitrogen doped Graphene through Noncovalent Molecular Functionalisation, Chem. Commun. 2016, 52, 10385-10388.
  5. K. S. K. Varadwaj, K. Seo, J. In, P. Mohanty, B. Kim, Phase controlled growth of metastable Fe5Si3 nanowires by a vapor transport Method, J. Am. Chem. Soc. 2007, 129, 8594-8599.

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Academics

Nano-Electrocatalysis Lab

Ph.D.

1. Biswaranjan Das Mohapatra

RGNF Fellow

Ph.D. awarded in 2019

Thesis Title: Exploring N-Doped Graphene as Support Material for Electrocatalytic Applications. He is a RGNF fellow and completed her M. Sc. in chemistry in 2012 from Ravenshaw University. 

Email: dasmohapatra.asish@gmail.com

SK1

2. Swarna Prava Mantry

CSIR-SRF fellow

Ph.D. awarded in 2020

Thesis Title: Understanding the Electrocatalytic Behavior of Nanostructured Manganese Oxide@ Graphene Based Hybrid Materials towards Oxygen Reduction Reaction. 

Email: spmantry@gmail.com

SK2

3. Nibedita Behera

RGNF Fellow

Ph.D. continuing

Her research topic is “Growth of functional molecules guided graphene oxide and their electrocatalytic Study”. She completed her M. Sc. in chemistry in 2012 from Ravenshaw University.

Email: beherasinu91@gmail.com

SK3

4. Dilip Kumar Mishra

Ph.D. Continuing

His research topic is “Silver nanowire based heterostructures for field emission and oxygen reduction applications”.

Email: dilip.mishra77@gmail.com

SK4

5. Rajesh Kumar Behera

Project JRF Fellow

Ph.D. Continuing

Email: rajeshbehera47@gmail.com

SK5

6. Subhashree Mongaraj

Ph.D. continuing

Email: subhashreemongaraj2016@gmail.com

SK6

7. Amarendra Nayak

GATE Qualified

Ph.D. Continuing 

Email: amarendranayak14@gmail.com

SK7

M. Phil

  1. Alaka Priyadarsini Sahoo (2020-Continuing)
  2. Sikha sayantini (2019-2020)
  3. Utkalika Padhi (2017-2018) 
  4. Prajnashree Panda (2017-2018)
  5. Ipsha Hota (2016-2017)
  6. Mayuri Giri (2016-2017) 
  7. Lipika Sahu (2015-2016)

Research

Electro-Materials Lab

OER Activity Trend in Co2Fe LDH‐N doped graphene hybrid

In the process of optimizing the Co2Fe LDH to N-graphene (NG) ratio to get enhanced oxygen evolution reaction (OER) activity in LDH@NG hybrids, we studied the activity trend with reference to various electrochemical and physical parameters. Among the studied samples OER activity increases with increase in amount of LDH loading and surprisingly, the samples with higher OER activity also show higher value of charge transfer resistance (RCT) at the electrode electrolyte interface. The hydrophilic nature of LDH surface, uniform distribution of LDH on NG and inhibition of NG stacking is proposed to be the reason behind the observed activity trend in the hybrid catalysts.

ORR Activity Decay and Regeneration

The oxygen reduction reaction (ORR) activity for Manganese oxide (MnOx) based nanostructures primarily depend upon their morphology, phase and surface Mn valency. After a prolonged used in fuel cells or metal air batteries, MnOx undergoes irreversible change with degradation in ORR activity. A methodology was developed for electrochemical regeneration of their ORR activity by potentiostatic conditioning. It has been observed that with the decay of ORR activity the characteristc redox peaks for MnOx dissapeared and the same reappeared after a potentiostatic treatment at -0.58 V in oxygen atmosphere.  It observed that decay in ORR activity was due to phase transformation to Mn3O4 with decrease in nominal Mn valency and drastic change in microstructure. Then the activity regeneration is due to regeneration of MnOOH phase and Mn valency.

Fe/Co/Ni doped MnOx @ Graphene Nanohybrid: A Comparative Study

Doping Manganese oxide with other transition metals is one of the intrinsic modifications to enhance the catalytic activity. Transition metal ions such as Fe, Co and Ni doped MnOx nanostructures on N-doped graphene increase average Mn valency thereby increasing electrocatalytic activity towards oxygen reduction. The cation doped samples show enhanced ORR activity in terms of onset potential, current density, electron transfer number, charge transfer resistance, and peroxide yield.

Projects:
  1. Design of New Complex Nanoheterostructure Electrocatalysts for Oxygen Reduction Reaction (ORR), SERB- SB/S1/PC-001/2013.
  2. Bridging the Understanding between Growth Pattern of Nanostructured Manganese Oxide polymorphs on Graphene and their Electrocatalytic Oxygen reduction Activity, DST, Odisha, Project no: 27562800512017/201304/ST.

Publications

  1. B. D. Mohapatra, I. Hota, S. P. Mantry, N. Behera, P. Parhi and K. S. K. Varadwaj, Understanding the oxygen evolution activity trend in Co2FeLDH-N doped graphene hybrids, Electrochem. Sci. Adv. 2020, doi:10.1002/elsa.202000009.
  2. I. Hota, A. K. Debnath, K. P. Muthe, K. S. K. Varadwaj, P. Parhi, Towards Synergy of rGO and Ni doped CeO2 in their composite as Efficient Catalyst for Oxygen Reduction Reaction, Chemistry Select, 2020, 22, 6608-6616.
  3. I. Hota, A. K. Debnath, K. P. Muthe, K. S. K. Varadwaj, P. Parhi, A synergistic approach of Vulcan carbon and CeO2in their composite as an efficient oxygen reduction reaction catalyst, Journal of Applied Electrochemistry, 2020, 50, 1069- 1077.
  4. N. Behera, S. P. Mantry, B. D. Mohapatra, R. K. Behera and K. S. K. Varadwaj, Functional molecule guided evolution of MnOx nanostructure patterns on N-graphene and their oxygen reduction activity, RSC Advances, 2019, 9, 27945–27952.
  5. S. P. Mantry, B. D. Mohapatra, N. Behera, P. Mishra, P. Parhi and K. S. K. Varadwaj, Potentiostatic Regeneration of oxygen reduction activity in MnOx@ Graphene hybrid nanostructures, Electrochimica Acta, 2019, 325, 134947.
  6. S. Soren, I. Hota, A. K. Debnath, D. K. Aswal, K. S. K. Varadwaj, P. Parhi, Oxygen Reduction Reaction Activity of Microwave Mediated Solvothermal Synthesized CeO2/g-C3N4Nanocomposite, Front. Chem., 2019, https://doi.org/10.3389/fchem.2019.00403.
  7. I. Hota, S. Soren, B. D. Mohapatra, A. K. Debnath, K. P. Muthe, K. S. K. Varadwaj, P. Parhi, Mn-doped ceria/reduced graphene oxide nanocomposite as an efficient oxygen reduction reaction catalyst, J. Electroanal Chem, 2019, 851, 113480.
  8. S. Soren, B. D. Mohapatra, S. Mishra, A. K. Debnath, D. K. Aswal, K. S. K. Varadwaj, P. Parhi, Nano ceria supported nitrogen doped graphene as a highly stable and methanol tolerant electrocatalyst for oxygen reduction,  RSC Advances, 2016, 6, 77100-77104.
  9. B. D. Mohapatra, S. P. Mantry, N. Behera, B. Behera, S. Rath and K. S. K. Varadwaj, Stimulation of Electrocatalytic Oxygen Reduction Activity on Nitrogen doped Graphene through Noncovalent Molecular Functionalisation, Chem. Commun. 2016, 52, 10385-10388. 
  10. J. Motohisa, K. Tomioka, B. Hua, K. S. K. Varadwaj, S. Hara, K. Hiruma and T. Fukui, III-V Semiconductor Nanowire Light Emitting Diodes and Lasers,in Advances in III-V Semiconductor Nanowires and Nanodevices, edited by J. Li, D. Wang, and R. R. LaPierre. (Bentham Science Publisher, 2011) Book Chapter.
  11. J. Motohisa, B. Hua, K. S. K. Varadwaj, S. Hara, K. Hiruma, T. Fukui; Lasing in GaAs-based nanowires grown by selective-area MOVPE; Photonics Society Winter Topicals Meeting Series (WTM), 2010 IEEE, 11-13 Jan. 2010,139 – 140.
  12. J. Motohisa, K. S. K. Varadwaj, K. Tomioka, T. Fukui; Optical properties and application of MOVPE-grown III-V nanowires; OptoeElectronics and Communications Conference (OECC), 2010 15th, 5-9 July 2010, 214 – 215.
  13. Y. Yoo, K. Seo, S. Han, Kumar S. K. Varadwaj, H. Kim, J. Ryu, H. Lee, J. Ahn, H. Ihee, B. Kim, Steering epitaxial alignment of Au, Pd, and AuPd nanowire arrays by atom flux change, Nano Letters, 2010, 10, 432. 
  14. K. Seo, S. Lee, H. Yoon, J. In, K. S. K. Varadwaj, Y. Jo, M-H Jung, J. Kim, B. Kim, Composition-Tuned ConSi Nanowires: Location-Selective Simultaneous Growth along Temperature Gradient. ACS Nano, 2009, 3, 1145. 
  15. H. Yoon, K. Seo, H. Moon, K. S. K. Varadwaj, J. In, B. Kim, Aluminum Foil Mediated Noncatalytic Growth of ZnO Nanowire Arrays on an Indium Tin Oxide Substrate, J. Phys. Chem. C, 2008, 112, 9181. 
  16. J. In, K. S. K. Varadwaj, K. Seo, S. Lee, Y. Jo, M-H Jung, J. Kim, and B. Kim, Synthesis and Magnetic Properties of Single Crystalline Fe1-xCoxSi Nanowires a Ferromagnetic Semiconductor, J. Phys. Chem. C, 2008, 112, 4748. 
  17. K. S. K. Varadwaj, K. Seo, J. In, P. Mohanty, B. Kim, Phase controlled growth of metastable Fe5Si3 nanowires by a vapor transport Method, J. Am. Chem. Soc. 2007, 129, 8594-8599. 
  18. K. Seo*, K. S. K. Varadwaj*, P. Mohanty, Y. Jo, M-H Jung, B. Kim, Magnetic properties of Single crystalline CoSi nanowires, Nano Letters, 2007, 7, 1240. (* These authors contributed equally to this work) 
  19. P. Mohanty, I. Yoon, T. Kang, K. Seo, K. S. K. Varadwaj, W. Choi, Q-H. Park, J. P. Ahn, H. Ihee, B. Kim, Simple Vapor Phase Synthesis of Single-Crystalline Ag Nanowires and Single-Nanowire Surface-Enhanced Raman Scattering,  J. Am. Chem. Soc. 2007, 129, 9576. 
  20. K. Seo,* K. S. K. Varadwaj,* D. Cha, J. In, J. Kim, J. Park, and B. Kim, Synthesis and electrical properties of single crystalline CrSi2 nanowires, J. Phys. Chem. C 2007, 111, 9072-9076.  (* These authors contributed equally to this work) 
  21. K. S. K. Varadwaj, J. Ghose, Effect of capping on the magnetization of nanocrystalline γ-Fe2O3, Ninth International Conference on Ferrites (ICF-9), pub. American Ceramic Society, 2004, p.841. 
  22. K. S. K. Varadwaj, J. Ghose, Synthesis and Characterisation of polyol capped transition metal oxide nanoparticles, Journal of Nanoscience and Nanotechnology, 2005, 5, 627-634. 
  23. K.S.K. Varadwaj, M. K. Panigrahi, J. Ghose, Effect of capping and particle size on Raman laser-induced degradation of γ-Fe2O3 nanoparticles, Journal of Solid State Chemistry, 2004, 177, 4286-4292. 
  24. 1. J. Ghose, K. S. K. Varadwaj, D. Das, Mössbauer Studies on Nanocrystalline Diol Capped γ-Fe2O3, Hyperfine Interactions, 2004, 156, 63-67.

Patent

  1. Jayasree Ghose; K. S. K. Varadwaj; “A process for the synthesis of capped nanocrystalline γ-Fe2O3” Indian Pat. Appl. (2005), 7pp. CODEN: INXXBQ IN 2003KO00320 A 20050204 CAN 147:413030 AN 2007:233059.

Teaching

  • Thermodynamics
  • General Electrochemistry
  • Electrodics
  • Phase Equilibria
  • Solid State Chemistry
  • X-ray diffraction