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Pathak, Biswarup
Publications (10 of 18) Show all publications
Qian, Z., Pathak, B. & Ahuja, R. (2013). Energetic and structural analysis of N2H4BH3 inorganic solid and its modified material for hydrogen storage. International journal of hydrogen energy, 38(16), 6718-6725
Open this publication in new window or tab >>Energetic and structural analysis of N2H4BH3 inorganic solid and its modified material for hydrogen storage
2013 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 38, no 16, p. 6718-6725Article in journal (Refereed) Published
Abstract [en]

Here we have exposed the electronic structure, chemical bonding of the light-weight N2H4BH3 inorganic material for hydrogen storage applications and analyzed its hydrogen removal energetics using state-of-the-art first-principles method. The mechanism for the H-host bond weakening in this kind of solid has also been explored. It is shown that the electronic density of states of N(2)H(4)BH(3)d solid near the Fermi level is mainly contributed by the B p-states, H (B) s-states, and the end N p-states. The calculated smallest hydrogen removal energy of N2H4BH3 solid is 4.16 eV. One Li-modified structure has been obtained through ab initio relaxations and its hydrogen removal energies are found dramatically decreased by as much as 50% compared with those of pristine N2H4BH3 solid. The B-H bond weakening is attributed to the elongation of the bond length; for the N H bonds, the weakening is found to be due to the destabilization of N-H bonds before hydrogen removal and the stabilization of residual N-H bond after hydrogen removal. The weakening of these bonds is of great significance for the improvement of hydrogen desorption kinetics of the material. We propose this study should help to deepen understanding of properties of N2H4BH3 inorganic solid and its related materials for hydrogen storage applications and guide experimentalists and engineers to develop better candidate materials for the advance of the field.

Keywords
Hydrogen storage material, Density functional theory, N2H4BH3 inorganic solid, Hydride, Hydrogen energy
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-203553 (URN)10.1016/j.ijhydene.2013.03.124 (DOI)000319958400018 ()
Available from: 2013-07-15 Created: 2013-07-15 Last updated: 2017-12-06Bibliographically approved
Jiang, X., Nisar, J., Pathak, B., Zhao, J. & Ahuja, R. (2013). Graphene oxide as a chemically tunable 2-D material for visible-light photocatalyst applications. Journal of Catalysis, 299, 204-209
Open this publication in new window or tab >>Graphene oxide as a chemically tunable 2-D material for visible-light photocatalyst applications
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2013 (English)In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 299, p. 204-209Article in journal (Refereed) Published
Abstract [en]

To elucidate the usage of graphene oxide (GO) as a photocatalysis material, we have studied the effect of epoxy and hydroxyl functionalization on the electronic structure, work function, CBM/VBM position, and optical absorption spectra of GO using density functional theory calculations. By varying the coverage and relative ratio of the surface epoxy (-O-) and hydroxyl (-OH) groups, both band gap and work function of the GO materials can be tuned to meet the requirement of photocatalyst. Interestingly, the electronic structures of GO materials with 40-50% (33-67%) coverage and OH:O ratio of 2:1(1:1) are suitable for both reduction and oxidation reactions for water splitting. Among of these systems, the GO composition with 50% coverage and OH:O (1:1) ratio can be very promising materials for visible-light-driven photocatalyst. Our results not only explain the recent experimental observations about 2-D graphene oxide as promising visible-light-driven photocatalyst materials but can also be very helpful in designing the optimal composition for higher performance.

Keywords
Ab initio calculation, Photolysis, Energy conversion, Renewable resource, Water splitting
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-198930 (URN)10.1016/j.jcat.2012.12.022 (DOI)000316774900021 ()
Available from: 2013-04-29 Created: 2013-04-29 Last updated: 2017-12-06Bibliographically approved
Prasongkit, J., Grigoriev, A., Pathak, B., Ahuja, R. & Scheicher, R. H. (2013). Theoretical Study of Electronic Transport through DNA Nucleotides in a Double-Functionalized Graphene Nanogap. The Journal of Physical Chemistry C, 117(29), 15421-15428
Open this publication in new window or tab >>Theoretical Study of Electronic Transport through DNA Nucleotides in a Double-Functionalized Graphene Nanogap
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2013 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 29, p. 15421-15428Article in journal (Refereed) Published
Abstract [en]

Graphene nanogaps and nanopores show potential for the purpose of electrical DNA sequencing, in particular because single-base resolution appears to be readily achievable. Here, we evaluated from first principles the advantages of a nanogap setup with functionalized graphene edges. To this end, we employed density functional theory and the non-equilibrium Green's function method to investigate the transverse conductance properties of the four nucleotides occurring in DNA when located between opposing functionalized graphene electrodes. In particular, we determined the electrical tunneling current variation as a function of the applied bias and analyzed the associated differential conductance at a voltage which appears suitable to distinguish between the four nucleotides. Intriguingly, we predict for one of the nucleotides (deoxyguanosine monophosphate) a negative differential resistance effect.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-208163 (URN)10.1021/jp4048743 (DOI)000322503600064 ()
Available from: 2013-09-24 Created: 2013-09-24 Last updated: 2017-12-06Bibliographically approved
Wang, B. C., Nisar, J., Pathak, B., Kang, T. W. & Ahuja, R. (2012). Band gap engineering in BiNbO4 for visible-light photocatalysis. Applied Physics Letters, 100(18), 182102
Open this publication in new window or tab >>Band gap engineering in BiNbO4 for visible-light photocatalysis
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2012 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 18, p. 182102-Article in journal (Refereed) Published
Abstract [en]

We have investigated the electronic structure of anionic mono- (S, N, and C) and co-doping (N-N, C-N, S-C, and S-N) on BiNbO4 for the visible-light photocatalysis. The maximum band gap reduction of pure BiNbO4 is possible with the (C-S) co-doping and minimum with N mono-doping. The calculated binding energies show that the co-doped systems are more stable than their mono-doped counterparts. Our optical absorption curves indicate that the mono- (C) and co-anionic doped (N-N and C-S) BiNbO4 systems are promising materials for visible light photocatalysis.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-174927 (URN)10.1063/1.4709488 (DOI)000303598600026 ()
Available from: 2012-05-30 Created: 2012-05-30 Last updated: 2017-12-07Bibliographically approved
Qian, Z., Li, S., Pathak, B., Araujo, C. M., Ahuja, R. & Jena, P. (2012). C-60-mediated hydrogen desorption in Li-N-H systems. Nanotechnology, 23(48), 485406
Open this publication in new window or tab >>C-60-mediated hydrogen desorption in Li-N-H systems
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2012 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 48, p. 485406-Article in journal (Refereed) Published
Abstract [en]

Hydrogen desorption from a LiH + NH3 mixture is very difficult due to the formation of the stable LiNH4 compound. Using cluster models and first-principles theory, we demonstrate that the C-60 molecule can in fact significantly improve the thermodynamics of ammonia-mediated hydrogen desorption from LiH due to the stabilization of the intermediate state, LiNH4. The hydrogen desorption following the path of LiNH4-C-60 -> LiNH3-C-60 + 1/2H(2) is exothermic. Molecular dynamic simulations show that this reaction can take place even at room temperature (300 K). In contrast, the stable LiNH4 compound cannot desorb hydrogen at room temperature in the absence of C-60. The introduction of C-60 also helps to restrain the NH3 gas which is poisonous in proton exchange membrane fuel cell applications.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-188389 (URN)10.1088/0957-4484/23/48/485406 (DOI)000311138100026 ()
Available from: 2012-12-19 Created: 2012-12-17 Last updated: 2017-12-06Bibliographically approved
Hussain, T., Pathak, B., Ramzan, M., Maark, T. A. & Ahuja, R. (2012). Calcium doped graphane as a hydrogen storage material. Applied Physics Letters, 100(18), 183902
Open this publication in new window or tab >>Calcium doped graphane as a hydrogen storage material
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2012 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 18, p. 183902-Article in journal (Refereed) Published
Abstract [en]

On the basis of first principle density functional theory, we have studied the stability, electronic structure, and hydrogen storage capacity of a monolayer calcium doped graphane (CHCa). The stability of CHCa was further investigated using the ab initio molecular dynamics study. The binding energy of Ca on graphane sheet was found to be higher than its bulk cohesive energy, which indicates the stability of CHCa. It was observed that with a doping concentration of 11.11% of Ca on graphane sheet, a reasonably good H-2 storage capacity of 6 wt. % could be attained. The adsorption energies of H-2 were found to be 0.1 eV, within the range of practical H-2 storage applications.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-174925 (URN)10.1063/1.4710526 (DOI)000303598600068 ()
Available from: 2012-05-30 Created: 2012-05-30 Last updated: 2017-12-07Bibliographically approved
Pathak, B., Löfås, H., Prasongkit, J., Grigoriev, A., Ahuja, R. & Scheicher, R. H. (2012). Double-functionalized nanopore-embedded gold electrodes for rapid DNA sequencing. Applied Physics Letters, 100(2), 023701
Open this publication in new window or tab >>Double-functionalized nanopore-embedded gold electrodes for rapid DNA sequencing
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2012 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 2, p. 023701-Article in journal (Refereed) Published
Abstract [en]

We have studied the effect of double-functionalization on gold electrodes for improving nanopore-based DNA sequencing. The functionalizing molecular probes are, respectively, capable of temporarily forming hydrogen bonds with both the nucleobase part and the phosphate group of the target DNA, thus potentially minimizing the structural fluctuations of a single-stranded DNA molecule passing between the gold electrodes. The results of our first-principles study indicate that the proposed setup yields current signals that differ by at least 1 order of magnitude for the four different nucleic acid bases, thus offering the possibility to electrically distinguish them.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-168591 (URN)10.1063/1.3673335 (DOI)000299126800091 ()
Available from: 2012-02-14 Created: 2012-02-13 Last updated: 2017-12-07Bibliographically approved
Kanhere, P., Nisar, J., Tang, Y., Pathak, B., Ahuja, R., Zheng, J. & Chen, Z. (2012). Electronic structure, optical properties and photocatalytic activities of LaFeO3-NaTaO3 solid solution. The Journal of Physical Chemistry C, 116(43), 22767-22773
Open this publication in new window or tab >>Electronic structure, optical properties and photocatalytic activities of LaFeO3-NaTaO3 solid solution
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2012 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 43, p. 22767-22773Article in journal (Refereed) Published
Abstract [en]

A solid solution photocatalyst, Na1–xLaxFe1–xTaxO3 (x up to 0.06), was prepared by the conventional solid-state method. The photophysical properties of the samples were studied by various experimental techniques and the electronic structures were investigated by using screened hybrid density functional (HSE06) calculations. The solid solution photocatalyst showed absorption of visible light extending up to 450 nm. Upon loading of platinum nanoparticles cocatalyst, the photocatalytic hydrogen evolution of 0.81 μ·mol·h–1·g–1 was obtained for 2% doping of LaFeO3 in NaTaO3, under visible radiation (λ > 390 nm; 20% methanol solution). The photocatalytic properties of the solid solution were found to be better than Fe doped NaTaO3 compounds on account of the suitable band structure. The electronic structure analysis revealed that, in the case of Fe doping at the Ta site, unoccupied electronic states in between the band gap appear that are responsible for the visible-light absorption. However, in the case of La and Fe codoping (passivated doping) the mid-gap electronic states are completely filled, which makes the band structure suitable for the visible-light photocatalysis. The present solid solution of perovskites (LaFeO3 and NaTaO3) sheds light on the interesting photophysical properties and photocatalytic activities which could be beneficial for the photocatalysts derived from these compounds.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2012
National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-179336 (URN)10.1021/jp307857h (DOI)000310482900014 ()
Funder
Swedish Research Council
Available from: 2012-08-13 Created: 2012-08-13 Last updated: 2017-12-07Bibliographically approved
Qian, Z., Hudson, M. S., Raghubanshi, H., Scheicher, R. H., Pathak, B., Araújo, C. M., . . . Ahuja, R. (2012). Excellent Catalytic Effects of Graphene Nanofibers on Hydrogen Release of Sodium alanate. The Journal of Physical Chemistry C, 116(20), 10861-10866
Open this publication in new window or tab >>Excellent Catalytic Effects of Graphene Nanofibers on Hydrogen Release of Sodium alanate
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2012 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 20, p. 10861-10866Article in journal (Refereed) Published
Abstract [en]

One of the most technically challenging barriers to the widespread commercialization of hydrogen-fueled devices and vehicles remains hydrogen storage. More environmentally friendly and effective nonmetal catalysts are required to improve hydrogen sorption. In this paper, through a combination of experiment and theory, we evaluate and explore the catalytic effects of layered graphene nanofibers toward hydrogen release of light metal hydrides such as sodium alanate. Graphene nanofibers, especially the helical kind, are found to considerably improve hydrogen release from NaAlH4, which is of significance for the further enhancement of this practical material for environmentally friendly and effective hydrogen storage applications. Using density functional theory, we find that carbon sheet edges, regardless of whether they are of zigzag or armchair type, can weaken Al-H bonds in sodium alanate, which is believed to be due to a combination of NaAlH4 destabilization and dissociation product stabilization. The helical form of graphene nanofibers, with larger surface area and curved configuration, appears to benefit the functionalization of carbon sheet edges. We believe that our combined experimental and theoretical study will stimulate more explorations of other microporous or mesoporous nanomaterials with an abundance of exposed carbon edges in the application of practical complex light metal hydride systems.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-176230 (URN)10.1021/jp300934h (DOI)000304338500004 ()
Available from: 2012-06-19 Created: 2012-06-18 Last updated: 2017-12-07Bibliographically approved
Hussain, T., Pathak, B., Maark, T. A., Ramzan, M. & Ahuja, R. (2012). Functionalization of graphane with alkali and alkaline-earth metals: An insulator-to-metallic transition. Europhysics letters, 99(4), 47004
Open this publication in new window or tab >>Functionalization of graphane with alkali and alkaline-earth metals: An insulator-to-metallic transition
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2012 (English)In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 99, no 4, p. 47004-Article in journal (Refereed) Published
Abstract [en]

In view of interest in functionalized carbon nanostructures due to their potential applications in nanotechnology and nanoelectronics, we have performed a systematic and thorough density functional theory (DFT) study on the interaction of the elements in the first two groups of the periodic table with graphane (hydrogenated graphene) sheet. GGA approximation as employed in DFT has been used to study in detail the binding configuration, bond length, charge transfer and band gap of each of these adatoms doped graphane (CH) systems. To have a better understanding of the adatoms-CH interaction, different doping concentrations varying from 3.125% to 50% have been considered. A certain trend in binding strength, bond length and charge transfer has been found in the case of both alkali metal and alkaline-earth metal adatoms. In the case of alkali-metal adatoms at the low doping concentration of 3.125%, semiconductor behavior was found, whereas at doping higher than this the compound showed metallic behavior. In contrast, alkaline-earth metal-doped CH exhibited metallic behavior at all the doping concentrations. Copyright (C) EPLA, 2012

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-183905 (URN)10.1209/0295-5075/99/47004 (DOI)000308376100023 ()
Available from: 2012-11-07 Created: 2012-11-05 Last updated: 2017-12-07Bibliographically approved
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