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Klaa, K., Labidi, S., Banerjee, A., Chakraborty, S., Labidi, M., Amara, A., . . . Ahuja, R. (2019). Composition dependent tuning of electronic and magnetic properties in transition metal substituted Rock-salt MgO. Journal of Magnetism and Magnetic Materials, 475, 44-53
Open this publication in new window or tab >>Composition dependent tuning of electronic and magnetic properties in transition metal substituted Rock-salt MgO
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2019 (English)In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 475, p. 44-53Article in journal (Refereed) Published
Abstract [en]

Full potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory (DFT) is used to investigate the structural, electronic and magnetic properties of Fe and Ni (3d transition metal) substituted Rock-salt wide band gap insulator Mg1-xMxO (M = Fe, Ni). We have performed spin polarized calculations throughout this work with generalized gradient approximation (GGA) type exchange correlation functional. Additionally, the electronic structures and density of states are computed using modified Becke-Johnson (mBJ) potential based approximation with the inclusion of coulomb energy (U = 7 eV). Based on the Vegard's law and structural optimization, the lattice parameter and bulk modulus are found to be in good agreement with experimental values. Moreover, the analysis of electronic band structures reveals an insulating character for Ni substituted MgO while semiconducting and half-metallic character for Fe substituted case. It has been found that the p-d super-exchange interaction provides a ferromagnetic character due to the 3d transition metal impurities and oxygen atom. The observed p-d hybridization at the top of the valence band edge in this investigations could be useful for magneto-optic and spintronic applications.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2019
Keywords
FP-LAPW, mBJ plus U, P-d exchange interaction, Half-metallic, Magnetic moment
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-378617 (URN)10.1016/j.jmmm.2018.11.065 (DOI)000458152000008 ()
Funder
Swedish Research CouncilCarl Tryggers foundation
Available from: 2019-03-11 Created: 2019-03-11 Last updated: 2019-03-11Bibliographically approved
Bashir, A., Lew, J. H., Shukla, S., Gupta, D., Baikie, T., Chakraborty, S., . . . Akhter, Z. (2019). Cu-doped nickel oxide interface layer with nanoscale thickness for efficient and highly stable printable carbon-based perovskite solar cell. Solar Energy, 182, 225-236
Open this publication in new window or tab >>Cu-doped nickel oxide interface layer with nanoscale thickness for efficient and highly stable printable carbon-based perovskite solar cell
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2019 (English)In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 182, p. 225-236Article in journal (Refereed) Published
Abstract [en]

The power conversion efficiency (PCE) of hole conductor free carbon-based perovskite solar cells (PSCs) is restricted by the poor charge extraction and recombination losses at the carbon-perovskite interface. For the first time we successfully demonstrated incorporation of thin layer of copper doped nickel oxide (Cu:NiOx) nanoparticles in carbon-based PSCs, which helps in improving the performance of these solar devices. Cu:NiOx nanoparticles have been synthesized by a facile chemical method, and processed into a paste for screen printing. Extensive X-ray Absorption Spectroscopy (XAS) analysis elucidates the co-ordination of Cu in a NiOx matrix and indicates the presence of around 5.4% Cu in the sample. We fabricated a monolithic perovskite module on a 100 cm(2) glass substrate (active area of 70 cm(2)) with a thin Cu:NiOx layer (80 nm), where the champion device shows an appreciated power conversion efficiency of 12.1% under an AM 1.5G illumination. To the best of our knowledge, this is the highest reported efficiency for such a large area perovskite solar device. I-V scans show that the introduction of Cu:NiOx mesoporous scaffold increases the photocurrent, and yields fill factor (FF) values exceeding 57% due to the better interface and increased hole extraction efficiency. Electrochemical Impedance Spectroscopy (EIS) results reinforce the above results by showing the reduction in recombination resistance (R-rec) of the PSCs that incorporates Cu:NiOx interlayer. The perovskite solar modules with a Cu:NiOx layer are stable for more than 4500 h in an ambient environment (25 degrees C and 65% RH), with PCE degradation of less than 5% of the initial value.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2019
Keywords
Perovskite, Cu:NiOx/NiOx, Carbon, Stability, Hole selectivity
National Category
Condensed Matter Physics Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-382519 (URN)10.1016/j.solener.2019.02.056 (DOI)000463130600022 ()
Available from: 2019-04-30 Created: 2019-04-30 Last updated: 2019-04-30Bibliographically approved
Watcharatharapong, T., T-Thienprasert, J., Chakraborty, S. & Ahuja, R. (2019). Defect formations and pH-dependent kinetics in krohnkite Na2Fe (SO4)2·2H2O based cathode for sodium-ion batteries: Resembling synthesis conditions through chemical potential landscape. Nano Energy, 55, 123-134
Open this publication in new window or tab >>Defect formations and pH-dependent kinetics in krohnkite Na2Fe (SO4)2·2H2O based cathode for sodium-ion batteries: Resembling synthesis conditions through chemical potential landscape
2019 (English)In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 55, p. 123-134Article in journal (Refereed) Published
Abstract [en]

Thermodynamics and kinetics of intrinsic point defects in Na2Fe(SO4)(2)center dot 2H(2)O, a high-voltage cathode for Na-ion batteries, are studied by means of first-principles density functional theory. Electronic structures of charged defects are calculated to study their influences towards electronic and electrochemical properties as well as to probe hole polaron formation. As defect formation energy strongly depends on atomic chemical potentials, we initiate a systematic approach to determine their valid ranges for the pentrary Na-Fe-S-O-H compound under thermodynamic equilibria and correlate them with approximated pH parameters in solution-based synthesis. Given chemical potential landscape and formation energy, we find that Fe-Na(1+), V-Na(1-,0) and Na-Fe(1-,0) are dominant and their concentrations could be manipulated through pH condition and oxygen content in the precursor solution. It is predicted that the channel blockage due to Fe-Na would appear under strong acidic growth condition but could be diminished under weak acidic condition (4.7 <= pH <= 5.6) where Na-Fe facilitates a faster migration between each diffusion channel. Our results do not only explain the origin of intercalation mechanism and improved electronic conduction, but also demonstrates the pH influence towards conductivities in the cathode material.

Keywords
Chemical potentials, Defects, DFT, Diffusions, Sodium-ion batteries
National Category
Materials Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-374115 (URN)10.1016/j.nanoen.2018.10.038 (DOI)000454636200012 ()
Funder
Swedish Research CouncilSwedish Research CouncilCarl Tryggers foundation
Available from: 2019-01-23 Created: 2019-01-23 Last updated: 2019-04-05Bibliographically approved
Das, T., Chakraborty, S., Ahuja, R. & Das, G. P. (2019). Functionalization and Defect-Driven Water Splitting Mechanism on a Quasi-Two-Dimensional TiO2 Hexagonal Nanosheet. ACS APPLIED ENERGY MATERIALS, 2(7), 5074-5082
Open this publication in new window or tab >>Functionalization and Defect-Driven Water Splitting Mechanism on a Quasi-Two-Dimensional TiO2 Hexagonal Nanosheet
2019 (English)In: ACS APPLIED ENERGY MATERIALS, ISSN 2574-0962, Vol. 2, no 7, p. 5074-5082Article in journal (Refereed) Published
Abstract [en]

In this work, we have dealt with the functionalization of a newly reported quasi-2D hexagonal nanosheet (HNS) of titanium dioxide (TiO2) for photocatalytic water splitting to generate hydrogen and oxygen. Functionalization has been carried out by creating a single oxygen vacancy defect as well as by incorporating substitutional doping with C, N, P, and S atoms at the O site of TiO2 HNS. The effects of functionalization and vacancy defects on the structural and electronic properties of HNS have been investigated by determining the corresponding projected density of states. It has been observed that functionalization causes a shift in the VBM and CBM of HNS, which in principle influences the catalytic activity. In addition, we have determined the work function for these materials in order to correlate them with the electrochemical activities of different considered HNSs. The catalytic activity has been predicted by determining the reaction coordinate as constructed from the free energies of the different reaction intermediates involved in HER and OER Among all of the systems that we have studied, HNS with an oxygen monovacancy has emerged as the best possible candidate for the water-splitting mechanism.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
Keywords
TiO2 HNS, oxygen vacancy, hydrogen evolution, work function, free energy, reaction pathway
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-391951 (URN)10.1021/acsaem.9b00745 (DOI)000477074700056 ()
Available from: 2019-08-28 Created: 2019-08-28 Last updated: 2019-08-28Bibliographically approved
Bera, S., Ghosh, D., Dutta, A., Bhattacharyya, S., Chakraborty, S. & Pradhan, N. (2019). Limiting Heterovalent B-Site Doping in CsPbI3 Nanocrystals: Phase and Optical Stability. ACS ENERGY LETTERS, 4(6), 1364-1369
Open this publication in new window or tab >>Limiting Heterovalent B-Site Doping in CsPbI3 Nanocrystals: Phase and Optical Stability
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2019 (English)In: ACS ENERGY LETTERS, ISSN 2380-8195, Vol. 4, no 6, p. 1364-1369Article in journal (Refereed) Published
Abstract [en]

B-site doping with various metal ions in alpha-CsPbI3 has been proven to be a potential approach in bringing phase stability to these nanocrystals. However, while the doping of various homovalent ions in replacing Pb(II) has been extensively studied, heterovalent doping was observed to be limited. To understand the impact of heterovalent doping, Sb(III) was chosen here as an effective dopant for occupying the Pb(II) position in CsPbI3 nanocrystals. Importantly, it was observed that insertion of Sb(III) also stabilized the crystal phase of these red-emitting nanocrystals, but only with limited doping. However, with more intake, the cube shape turned to platelet and therefore also reduced the stability. Details of the insights of formation of these doped nanostructures are investigated, and further, these were implemented for photovoltaic application and comparable efficiency was recorded.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-390216 (URN)10.1021/acsenergylett.9b00787 (DOI)000472121800020 ()
Available from: 2019-08-07 Created: 2019-08-07 Last updated: 2019-08-07Bibliographically approved
Watcharatharapong, T., Chakraborty, S. & Ahuja, R. (2019). Mapping Sodium Intercalation Mechanism, Electrochemical Properties and Structural Evolution in Non-stoichiometric Alluaudite Na2+2δFe2-δ(SO4)3 Cathode Materials. Journal of Materials Chemistry A, 7, 17446-17455
Open this publication in new window or tab >>Mapping Sodium Intercalation Mechanism, Electrochemical Properties and Structural Evolution in Non-stoichiometric Alluaudite Na2+2δFe2-δ(SO4)3 Cathode Materials
2019 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 7, p. 17446-17455Article in journal (Refereed) Published
Abstract [en]

In the scientific advancement of future cathode materials, alluaudite sodium iron sulfate Na2+2δFe2−δ(SO4)3 (NxFyS) has emerged as one of the most promising candidates for sustainable sodium-ion batteries due to its high Fe2+/3+ redox potential (3.8 V vs.Na/Na+), low cost, and high rate capability. Usually, this material occurs in a non-stoichiometric form with partial Na+ substitutions on Fe sites, where δ is close to 0.25 (N2.5F1.75S) depending on the synthesis conditions. While many contemporary works have primarily been directed to study this non-stoichiometric compound, our previous theoretical prediction unveiled the possibility to synthesize stoichiometric alluaudite (N2F2S), which is expected to deliver higher specific capacity (∼120 mA h g−1) as compared to the non-stoichiometric derivatives. This provokes curiosity toward the non-stoichiometric effect on the electrochemical activities and sodium intercalation mechanism in alluaudite materials. In this work, we therefore perform rigorous first-principles calculations to study the structural evolution, electrochemical behavior, and voltage profile of NxFyS with y = 2, 1.75, and 1.5. We reveal the likelihood of two phase transitions after half desodiation process, whereas the probability is reduced with a higher degree of non-stoichiometry, suggesting improvement in the structural reversibility for N2.5F1.75S and N3F1.5S. The prediction of the voltage profiles shows the benefit of non-stoichiometry in enhancing the specific capacity and identifies the structural rearrangement of Fe2O10 dimers as the hidden reason behind the irreversible sharp peak experimentally observed in differential galvanostatic profiles.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-381172 (URN)10.1039/c9ta03930a (DOI)000476913600026 ()
Funder
Swedish Research CouncilStandUpCarl Tryggers foundation
Available from: 2019-04-05 Created: 2019-04-05 Last updated: 2019-08-22Bibliographically approved
Minakshi, M., Mitchell, D. R. G., Baur, C., Chable, J., Barlow, A. J., Fichtner, M., . . . Ahuja, R. (2019). Phase evolution in calcium molybdate nanoparticles as a function of synthesis temperature and its electrochemical effect on energy storage. NANOSCALE ADVANCES, 1(2), 565-580
Open this publication in new window or tab >>Phase evolution in calcium molybdate nanoparticles as a function of synthesis temperature and its electrochemical effect on energy storage
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2019 (English)In: NANOSCALE ADVANCES, ISSN 2516-0230, Vol. 1, no 2, p. 565-580Article in journal (Refereed) Published
Abstract [en]

The design of a suitable electrode is an essential and fundamental research challenge in the field of electrochemical energy storage because the electronic structures and morphologies determine the surface redox reactions. Calcium molybdate (CaMoO4) was synthesized by a combustion route at 300 degrees C and 500 degrees C. We describe new findings on the behaviour of CaMoO4 and evaluate the influence of crystallinity on energy storage performance. A wide range of characterization techniques was used to obtain detailed information about the physical and morphological characteristics of CaMoO4. The characterization results enable the phase evolution as a function of the electrode synthesis temperature to be understood. The crystallinity of the materials was found to increase with increasing temperature but with no second phases observed. Molecular dynamics simulation of electronic structures correlated well with the experimental findings. These results show that to enable faster energy storage and release for a given surface area, amorphous CaMoO4 is required, while larger energy storage can be obtained by using crystalline CaMoO4. CaMoO4 has been evaluated as a cathode material in classical lithium-ion batteries recently. However, determining the surface properties in a sodium-ion system experimentally, combined with computational modelling to understand the results has not been reported. The superior electrochemical properties of crystalline CaMoO4 are attributed to its morphology providing enhanced Na+ ion diffusivity and electron transport. However, the presence of carbon in amorphous CaMoO4 resulted in excellent rate capability, suitable for supercapacitor applications.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2019
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-393014 (URN)10.1039/c8na00156a (DOI)000479170600016 ()
Funder
Swedish Research CouncilCarl Tryggers foundation
Available from: 2019-09-19 Created: 2019-09-19 Last updated: 2019-09-19Bibliographically approved
Das, T., Chakraborty, S., Ahuja, R. & Das, G. P. (2019). TiS2 Monolayer as an Emerging Ultrathin Bifunctional Catalyst: Influence of Defects and Functionalization. ChemPhysChem, 20(4), 608-617
Open this publication in new window or tab >>TiS2 Monolayer as an Emerging Ultrathin Bifunctional Catalyst: Influence of Defects and Functionalization
2019 (English)In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 20, no 4, p. 608-617Article in journal (Refereed) Published
Abstract [en]

We have envisaged the hydrogen evolution and oxygen evolution reactions (HER and OER) on a two‐dimensional (2D) noble‐metal‐free titanium disulfide (TiS2) monolayer, which belongs to the exciting family of transition metal dichalcogenides (TMDCs). Our theoretical investigation to probe the HER and OER on both the H and T phases of 2D TiS2 is based on electronic‐structure calculations witihin the framework of density functional theory (DFT). Since TiS2 is the lightest compound among the group‐IV TMDCs, it is worth exploring the catalytic activity of a TiS2 monolayer through the functionalization at the anion (S) site, substituting with P, N, and C dopants as well as by incorporating single sulfur vacancy defects. We have investigated the effect of functionalization and vacancy defects on the structural, electronic, and optical response of a TiS2 monolayer by determining the density of states, work‐function, and optical absorption spectra. We have determined the HER and OER activities for the functionalized and defective TiS2 monolayers based on the reaction coordinate, which can be constructed from the adsorption free energies of the intermediates (H*, O*, OH* and OOH*, where * denotes the adosrbed state) in the HER and OER mechanisms. Finally, we have shown that TiS2 monolayers are emerging as a promising material for the HER and OER mechanisms under the influence of functionalization and defects.

Keywords
Bifunctional Catalysts, Density Functional Theory, HER and OER, Reaction Coordinates, TiS2 monolayers
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-378992 (URN)10.1002/cphc.201801031 (DOI)000458952600015 ()30552837 (PubMedID)
Funder
Swedish Research CouncilCarl Tryggers foundation
Available from: 2019-03-19 Created: 2019-03-19 Last updated: 2019-03-19Bibliographically approved
Pious, J. K., Katre, A., Muthu, C., Chakraborty, S., Krishna, S. & Nair, V. C. (2019). Zero-Dimensional Lead-Free Hybrid Perovskite-like Material with a Quantum-Well Structure. Chemistry of Materials, 31(6), 1941-1945
Open this publication in new window or tab >>Zero-Dimensional Lead-Free Hybrid Perovskite-like Material with a Quantum-Well Structure
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2019 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, no 6, p. 1941-1945Article in journal (Refereed) Published
Abstract [en]

Low-dimensional perovskites are an emerging class of materials with high stability and excellent optoelectronic properties. Herein, we introduce a novel, lead-free, zero-dimensional perovskite-like material, (1,3-propanediammonium)(2)Bi2I10 center dot 2H(2)O, for optoelectronic applications. This material exhibited good moisture and thermal stability under ambient conditions. Single-crystal X-ray diffraction analysis revealed a quantum-well structure having the inorganic Bi2I104- clusters periodically arranged in the crystallographic "c" axis separated by a distance of 5.36 angstrom, sandwiched by independent layers of organic cations. The density functional theory calculations showed that the oxygen in water molecules has a significant contribution to the band edges of the material. The photodetector device fabricated using this material showed an efficient charge separation at low voltage (1 V) due to the good electronic conduction between the Bi2I104- dimer units.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-382454 (URN)10.1021/acs.chemmater.8b04642 (DOI)000462950400012 ()
Available from: 2019-05-10 Created: 2019-05-10 Last updated: 2019-05-10Bibliographically approved
Minakshi, M., Watcharatharapong, T., Chakraborty, S. & Ahuja, R. (2018). A combined theoretical and experimental approach of a new ternary metal oxide in molybdate composite for hybrid energy storage capacitors. APL MATERIALS, 6(4), Article ID 047701.
Open this publication in new window or tab >>A combined theoretical and experimental approach of a new ternary metal oxide in molybdate composite for hybrid energy storage capacitors
2018 (English)In: APL MATERIALS, ISSN 2166-532X, Vol. 6, no 4, article id 047701Article in journal (Refereed) Published
Abstract [en]

Sustainable energy sources require an efficient energy storage system possessing excellent electrochemical properties. The better understanding of possible crystal configurations and the development of a new ternary metal oxide in molybdate composite as an electrode for hybrid capacitors can lead to an efficient energy storage system. Here, we reported a new ternary metal oxide in molybdate composite [(Mn1/3Co1/3Ni1/3)MoO4] prepared by simple combustion synthesis with an extended voltage window (1.8 V vs. Carbon) resulting in excellent specific capacity 35 C g−1 (58 F g−1) and energy density (50 Wh kg−1 at 500 W kg−1) for a two electrode system in an aqueous NaOH electrolyte. The binding energies measured for Mn, Co, and Ni 2p are consistent with the literature, and with the metal ions being present as M(II), implying that the oxidation states of the transition metals are unchanged. The experimental findings are correlated well through density functional theory based electronic structure calculations. Our reported work on the ternary metal oxide studies (Mn1/3Co1/3Ni1/3)MoO4 suggests that will be an added value to the materials for energy storage.

National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-355692 (URN)10.1063/1.4994750 (DOI)000431141500010 ()
Available from: 2018-07-04 Created: 2018-07-04 Last updated: 2019-04-05Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-6765-2084

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