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Publications (10 of 508) Show all publications
Mir, S. H., Chakraborty, S., Wärnå, J., Narayan, S., Jha, P. C., Jha, P. K. & Ahuja, R. (2017). A comparative study of hydrogen evolution reaction on pseudo-monolayer WS2 and PtS2: insights based on the density functional theory. Catalysis Science & Technology, 7(3), 687-692.
Open this publication in new window or tab >>A comparative study of hydrogen evolution reaction on pseudo-monolayer WS2 and PtS2: insights based on the density functional theory
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2017 (English)In: Catalysis Science & Technology, ISSN 2044-4753, E-ISSN 2044-4761, Vol. 7, no 3, 687-692 p.Article in journal (Refereed) Published
Abstract [en]

In this study, we investigated the catalytic activity of ultrathin PtS2 and WS2 nanostructures for the hydrogen evolution reaction by electronic structure calculations based on the spin-polarised density functional theory. We also explored the effect of van der Waals interactions on the surface-adsorbate interactions. Using the adsorption free energy of H-2 as an activity descriptor, we tuned the photocatalytic water splitting activity of PtS2 and WS2 by functionalizing the individual systems with different transition metals such as Ru, Rh, Pd, Ag, Ir, Au, and Hg. The density of states was calculated along with the band structure to find the effect of different dopants on the fundamental band gap, which is one of the primary parameters in the photocatalytic water splitting.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-320468 (URN)10.1039/c6cy02426b (DOI)000398053000017 ()
Available from: 2017-04-26 Created: 2017-04-26 Last updated: 2017-04-26Bibliographically approved
Qian, Z., Raghubanshi, H., Hudson, M. S., Srivastava, O. N., Liu, X. & Ahuja, R. (2017). Ab initio insight into graphene nanofibers to destabilize hydrazine borane for hydrogen release. Chemical Physics Letters, 669, 110-114.
Open this publication in new window or tab >>Ab initio insight into graphene nanofibers to destabilize hydrazine borane for hydrogen release
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2017 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 669, 110-114 p.Article in journal (Refereed) Published
Abstract [en]

We report the potential destabilizing effects of graphene nanofibers on the hydrogen release property of hydrazine borane via state-of-the-art ab initio calculations for the first time. Interactions of a hydrazine borane cluster with two types of graphene patch edges which exist abundantly in our synthesized graphene nanofibers have been investigated. It is found that both zigzag and armchair edges can greatly weaken the H-host bonds (especially the middle N-H bond) of hydrazine borane. The dramatic decrease in hydrogen removal energy is caused by the strong interaction between hydrazine borane and the graphene patch edges concerning the electronic charge density redistribution.

Keyword
Energy storage, Destabilization, Nanostructured materials, Density functional theory
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-316940 (URN)10.1016/j.cplett.2016.12.043 (DOI)000392774900016 ()
Funder
Swedish Research Council
Available from: 2017-03-09 Created: 2017-03-09 Last updated: 2017-11-29Bibliographically approved
Sun, W., Luo, W., Feng, Q. & Ahuja, R. (2017). Anisotropic distortion and Lifshitz transition in alpha-Hf under pressure. Physical Review B, 95(11), Article ID 115130.
Open this publication in new window or tab >>Anisotropic distortion and Lifshitz transition in alpha-Hf under pressure
2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, no 11, 115130Article in journal (Refereed) Published
Abstract [en]

In this work we report a theoretical investigation on behavior of the elastic constant C-44 and the transverse optical phonon mode E(2)g of a-Hf under pressure within the density functional theory. In contrast to many other reported transition metals, the above two quantities do not show a synchronous relation as pressure increases. Below 13 GPa, an opposite shifting tendency has been observed. However, once the pressure is raised above 13 GPa, the trend is pulled back to be consistent. This anomalous behavior is figured out to be caused by the large lattice anisotropy of the c/a ratio along with the elastic anisotropy. The synchronous behavior is found to be in accordance with the behavior of c/a ratio with increased pressure. In our band-structure investigations the electronic topological transition has been discovered at 10 GPa, which relates to the change of c/a ratio suggested by recent literature. The presence of the Van Hove singularity shown in the densities of states has been identified and regarded as the origin of the variation of C-44 and E(2)g.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2017
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-320218 (URN)10.1103/PhysRevB.95.115130 (DOI)000396273400004 ()
Funder
Swedish Research Council
Available from: 2017-04-18 Created: 2017-04-18 Last updated: 2017-11-29Bibliographically approved
Araujo, R. B., Banerjee, A., Panigrahi, P., Yang, L., Sjödin, M., Strömme, M., . . . Ahuja, R. (2017). Assessing Electrochemical Properties of Polypyridine and Polythiophene for Prospective Application in Sustainable Organic Batteries. Physical Chemistry, Chemical Physics - PCCP, 19(4), 3307-3314.
Open this publication in new window or tab >>Assessing Electrochemical Properties of Polypyridine and Polythiophene for Prospective Application in Sustainable Organic Batteries
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2017 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 4, 3307-3314 p.Article in journal (Refereed) Published
Abstract [en]

Conducting polymers are being considered promising candidates for sustainable organic batteries mainly due to their fast electron transport properties and high recyclability. In this work, key properties of polythiophene and polypyridine have been assessed through a combined theoretical and experimental study focusing on such applications. A theoretical protocol has been developed to calculate redox potentials in solution within the framework of the density functional theory and using continuous solvation models. Here, the evolution of the electrochemical properties of solvated oligomers as a function of the length of the chain is analyzed and then the polymer properties are estimated via linear regressions using ordinary least square. The predicted values were verified against our electrochemical experiments. This protocol can now be employed to screen a large database of compounds in order to identify organic electrodes with superior properties.

National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-311276 (URN)10.1039/C6CP07435A (DOI)000394940400071 ()28091636 (PubMedID)
Funder
Swedish Foundation for Strategic Research Swedish Energy AgencyStandUpSwedish Research Council
Available from: 2016-12-22 Created: 2016-12-22 Last updated: 2017-10-19Bibliographically approved
Jena, N. K., Araujo, R. B., Shukla, V. & Ahuja, R. (2017). Borophane as a Benchmate of Graphene: A Potential 2D Material for Anode of Li and Na-Ion Batteries. ACS Applied Materials and Interfaces, 9(19), 16148-16158.
Open this publication in new window or tab >>Borophane as a Benchmate of Graphene: A Potential 2D Material for Anode of Li and Na-Ion Batteries
2017 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 19, 16148-16158 p.Article in journal (Refereed) Published
Abstract [en]

Borophene, single atomic-layer sheet of boron (Science 2015, 350, 1513), is a rather new entrant into the burgeoning class of 2D materials. Borophene exhibits anisotropic metallic properties whereas its hydrogenated counterpart borophane is reported to be a gapless Dirac material lying on the same bench with the celebrated graphene. Interestingly, this transition of borophane also rendered stability to it considering the fact that borophene was synthesized under ultrahigh vacuum conditions on a metallic (Ag) substrate. On the basis of first-principles density functional theory computations, we have investigated the possibilities of borophane as a potential Li/Na-ion battery anode material. We obtained a binding energy of -2.58 (-1.08 eV) eV for Li (Na)-adatom on borophane and Bader charge analysis revealed that Li(Na) atom exists in Li+(Na+) state. Further, on binding with Li/Na, borophane exhibited metallic properties as evidenced by the electronic band structure. We found that diffusion pathways for Li/Na on the borophane surface are anisotropic with x direction being the favorable one with a barrier of 0.27 and 0.09 eV, respectively. While assessing the Li-ion anode performance, we estimated that the maximum Li content is Li0.445B2H2, which gives rises to a material with a maximum theoretical specific capacity of 504 mAh/g together with an average voltage of 0.43 V versus Li/Li+. Likewise, for Na-ion the maximum theoretical capacity and average voltage were estimated to be 504 mAh/g and 0.03 V versus Na/Na+, respectively. These findings unambiguously suggest that borophane can be a potential addition to the map of Li and Na-ion anode materials and can rival some of the recently reported 2D materials including graphene.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2017
Keyword
borophene, borophane, Dirac material, Li-ion battery, Na-ion battery, Li/Na-diffusion
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-327151 (URN)10.1021/acsami.7b01421 (DOI)000401782500026 ()28443653 (PubMedID)
Funder
Swedish Research CouncilStandUpCarl Tryggers foundation
Available from: 2017-08-25 Created: 2017-08-25 Last updated: 2017-10-19Bibliographically approved
Banerjee, A., Chakraborty, S. & Ahuja, R. (2017). Bromination-induced stability enhancement with a multivalley optical response signature in guanidinium [C(NH2)(3)](+)-based hybrid perovskite solar cells. Journal of Materials Chemistry A, 5(35), 18561-18568.
Open this publication in new window or tab >>Bromination-induced stability enhancement with a multivalley optical response signature in guanidinium [C(NH2)(3)](+)-based hybrid perovskite solar cells
2017 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 5, no 35, 18561-18568 p.Article in journal (Refereed) Published
Abstract [en]

Guanidinium lead iodide (GAPbI(3)) has been synthesized experimentally, but stability remains an issue, which can be modulated by the insertion of bromine (Br) into the system. We have performed a systematic theoretical investigation to see how bromination can tune the stability of GAPbI(3). The optical properties were also determined, and we have found formation enthalpy-based stability in the perovskite systems, which are active in the visible and IR region even after bromine insertion and additionally more active in the IR range with the transition from GAPbI(3) to GAPbBr(3). The spin orbit coupling effect is considered throughout the band structure calculations. The ensemble of the primary and secondary gaps in the half and fully brominated hybrid perovskites leads to the phenomenon of a multipeak response in the optical spectra, which can be subsequently attributed as multivalley optical response behaviour. This multivalley optical behaviour enables the brominated guanidinium-based hybrid perovskites to exhibit broad light harvesting abilities, and this can be perceived as an idea for natural multi-junction solar cells.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-336031 (URN)10.1039/c7ta03114a (DOI)000410597200026 ()
Funder
Carl Tryggers foundation Swedish Research CouncilSwedish Energy AgencyStandUp
Available from: 2017-12-13 Created: 2017-12-13 Last updated: 2017-12-13Bibliographically approved
Yuldashev, S. U. U., Yunusov, Z. A., Kwon, Y. H., Lee, S. H., Ahuja, R. & Kang, T. W. (2017). Critical behavior of the resistivity of GaMnAs near the Curie temperature. Solid State Communications, 263, 38-41.
Open this publication in new window or tab >>Critical behavior of the resistivity of GaMnAs near the Curie temperature
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2017 (English)In: Solid State Communications, ISSN 0038-1098, E-ISSN 1879-2766, Vol. 263, 38-41 p.Article in journal (Refereed) Published
Abstract [en]

The effect of the magnetization fluctuations on the resistivity of GaMnAs near the Curie temperature T-C was experimentally studied. It is shown that the determination of T-C from the maximum of the temperature derivative of the resistivity is valid for the samples with a high concentration of free carries. Whereas, for the samples with low concentration of free carriers the T-C coincides with the resistivity maximum. The magnetic specific heat for T > T-C demonstrates the crossover from the one dimensional to the three dimensional critical behavior when the temperature become closer to the Curie temperature. This is explained by the formation of the ferromagnetic phase in the paramagnetic side of the phase transition which is started from Mn-Mn dimers oriented along one direction.

Keyword
GaMnAs, Diluted magnetic semiconductor, Phase transition, Critical behavior
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-335749 (URN)10.1016/j.ssc.2017.07.005 (DOI)000410842900008 ()
Available from: 2017-12-08 Created: 2017-12-08 Last updated: 2017-12-08Bibliographically approved
Araujo, R. B., Banerjee, A., Panigrahi, P., Yang, L., Strömme, M., Sjödin, M., . . . Ahuja, R. (2017). Designing strategies to tune reduction potential of organic molecules for sustainable high capacity batteries application. Journal of Materials Chemistry A, 5(9), 4430-4454.
Open this publication in new window or tab >>Designing strategies to tune reduction potential of organic molecules for sustainable high capacity batteries application
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2017 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 5, no 9, 4430-4454 p.Article in journal (Refereed) Published
Abstract [en]

Organic compounds evolve as a promising alternative to the currently used inorganic materials in rechargeable batteries due to their low-cost, environmentally friendliness and flexibility. One of the strategies to reach acceptable energy densities and to deal with the high solubility of known organic compounds is to combine small redox active molecules, acting as capacity carrying centres, with conducting polymers. Following this strategy, it is important to achieve redox matching between the chosen molecule and the polymer backbone. Here, a synergetic approach combining theory and experiment has been employed to investigate this strategy. The framework of density functional theory connected with the reaction field method has been applied to predict the formal potential of 137 molecules and identify promising candidates for the referent application. The effects of including different ring types, e.g. fused rings or bonded rings, heteroatoms, [small pi] bonds, as well as carboxyl groups on the formal potential, has been rationalized. Finally, we have identified a number of molecules with acceptable theoretical capacities that show redox matching with thiophene-based conducting polymers which, hence, are suggested as pendent groups for the development of conducting redox polymer based electrode materials.

National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-314502 (URN)10.1039/C6TA09760J (DOI)000395926100022 ()
Funder
Swedish Foundation for Strategic Research Swedish Energy AgencyStandUpSwedish Research Council
Available from: 2017-02-02 Created: 2017-02-02 Last updated: 2017-10-19Bibliographically approved
Triana, C. A., Araujo, C. M., Ahuja, R., Niklasson, G. A. & Edvinsson, T. (2017). Disentangling the intricate atomic short-range order and electronic properties in amorphous transition metal oxides. Scientific Reports, 7, Article ID 2044.
Open this publication in new window or tab >>Disentangling the intricate atomic short-range order and electronic properties in amorphous transition metal oxides
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2017 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, 2044Article in journal (Refereed) Published
Abstract [en]

Solid state materials with crystalline order have been well-known and characterized for almost a century while the description of disordered materials still bears significant challenges. Among these are the atomic short-range order and electronic properties of amorphous transition metal oxides [aTMOs], that have emerged as novel multifunctional materials due to their optical switching properties and high-capacity to intercalate alkali metal ions at low voltages. For decades, research on aTMOs has dealt with technological optimization. However, it remains challenging to unveil their intricate atomic short-range order. Currently, no systematic and broadly applicable methods exist to assess atomic-size structure, and since electronic localization is structure-dependent, still there are not well-established optical and electronic mechanisms for modelling the properties of aTMOs. We present state-of-the-art systematic procedures involving theory and experiment in a self-consistent computational framework to unveil the atomic short-range order and its role for the electronic properties. The scheme is applied to amorphous tungsten trioxide aWO(3), which is the most studied electrochromic aTMO in spite of its unidentified atomic-size structure. Our approach provides a one-to-one matching of experimental data and corresponding model structure from which electronic properties can be directly calculated in agreement with the electronic transitions observed in the XANES spectra.

National Category
Condensed Matter Physics Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-318191 (URN)10.1038/s41598-017-01151-2 (DOI)000401511100051 ()28515466 (PubMedID)
Funder
Swedish Research CouncilKnut and Alice Wallenberg Foundation
Available from: 2017-03-23 Created: 2017-03-23 Last updated: 2017-06-27Bibliographically approved
Araujo, R. B., Banerjee, A. & Ahuja, R. (2017). Divulging the Hidden Capacity and Sodiation Kinetics of NaxC6Cl4O2: A High Voltage Organic Cathode for Sodium Rechargeable Batteries. The Journal of Physical Chemistry C, 121(26), 14027-14036.
Open this publication in new window or tab >>Divulging the Hidden Capacity and Sodiation Kinetics of NaxC6Cl4O2: A High Voltage Organic Cathode for Sodium Rechargeable Batteries
2017 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 26, 14027-14036 p.Article in journal (Refereed) Published
Abstract [en]

In the current emerging sustainable organic battery field, quinones are seen as one of the prime candidates for application in rechargeable battery electrodes. Recently, C6Cl4O2, a modified quinone, has been proposed as a high voltage organic cathode. However, the sodium insertion mechanism behind the cell reaction remained unclear due to the nescience of the right crystal structure. Here, the framework of the density functional theory (DFT) together with an evolutionary algorithm was employed to elucidate the crystal structures of the compounds NaxC6Cl4O2 (x = 0.5, 1.0, 1.5 and 2). Along with the usefulness of PBE functional to reflect the experimental potential, also the importance of the hybrid functional to divulge the hidden theoretical capacity is evaluated. We showed that the experimentally observed lower specific capacity is a result of the great stabilization of the intermediate phase Na1.5C6Cl4O2. The calculated activation barriers for the ionic hops are 0.68, 0.40, and 0.31 eV, respectively, for NaC6Cl4O2, Na1.5C6Cl4O2, and Na2C6Cl4O2. These results indicate that the kinetic process must not be a limiting factor upon Na insertion. Finally, the correct prediction of the specific capacity has confirmed that the theoretical strategy used, employing evolutionary simulations together with the hybrid functional framework, can rightly model the thermodynamic process in organic electrode compounds.

National Category
Materials Engineering Physical Sciences
Identifiers
urn:nbn:se:uu:diva-329995 (URN)10.1021/acs.jpcc.7b03621 (DOI)000405252800007 ()
Funder
Swedish Energy AgencySwedish Research CouncilStandUp
Note

Divulging the Hidden Capacity and Sodiation Kinetics of NaxC6Cl4O2: A High Voltage Organic Cathode for Sodium Rechargeable Batteries

Available from: 2017-10-13 Created: 2017-10-13 Last updated: 2017-10-19Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-1231-9994

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