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Sharifi, Tiva
Publications (10 of 31) Show all publications
Moradifar, P., Nixon, A. G., Sharifi, T., van Driel, T. B., Ajayan, P., Masiello, D. J. & Alem, N. (2022). Nanoscale Mapping and Defect-Assisted Manipulation of Surface Plasmon Resonances in 2D Bi2Te3/Sb2Te3 In-Plane Heterostructures. Advanced Optical Materials, 10(10), Article ID 2101968.
Open this publication in new window or tab >>Nanoscale Mapping and Defect-Assisted Manipulation of Surface Plasmon Resonances in 2D Bi2Te3/Sb2Te3 In-Plane Heterostructures
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2022 (English)In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 10, no 10, article id 2101968Article in journal (Refereed) Published
Abstract [en]

The Bi2Te3/Sb2Te3 in-plane heterostructure is reported as a low-dimensional tunable chalcogenide well suited as plasmonic building block for the visible−UV spectral range. Electron-driven plasmon excitations of low-dimensional Bi2Te3/Sb2Te3 are investigated by monochromated electron energy loss spectroscopy spectrum imaging. To resolve the nanoscale spatial distribution of various local plasmonic resonances, singular value decomposition is used to disentangle the spectral data and identify the individual spectral contributions of various corner, edge, and face modes. Furthermore, defect-plasmon interactions are investigated both for nanoscale intrinsic and thermally induced extrinsic polygonal defects (in situ sublimation). Signature of defect-induced red shift ranging from a several hundreds of millielectronvolts to a few electronvolts, broadening of various plasmon response, together with selective enhancement and significant variations in their intensity are detected. This study highlights the presence of a heterointerface and identifies defects as physical tuning pathways to modulate the plasmonic response over a broad spectral range. Finally, the experimental observations are compared qualitatively and validated with numerical simulations using the electron-driven discrete dipole approximation. Low-dimensional Bi2Te3/Sb2Te3 as a less explored plasmonic system holds great promises as emerging platform for integrated plasmonics. Furthermore, introducing controlled structural defects can open the door for nanoengineering of plasmonic properties in such systems.

Place, publisher, year, edition, pages
John Wiley & Sons, 2022
Keywords
Bi 2Te 3/Sb 2Te 3, defect-plasmon interaction, electron-driven discrete dipole approximation (e-DDA), low-dimensional tunable chalcogenides, monochromated electron energy loss spectroscopy (Mono-EELS), singular value decomposition (SVD), surface plasmon resonance
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-193589 (URN)10.1002/adom.202101968 (DOI)000772484500001 ()2-s2.0-85126983480 (Scopus ID)
Funder
Swedish Research Council, 2015-06462
Note

This article also appears in Hot Topic: Surfaces and Interfaces.

Available from: 2022-04-19 Created: 2022-04-19 Last updated: 2022-07-13Bibliographically approved
Sharifi, T., Gracia-Espino, E., Chen, A., Hu, G. & Wågberg, T. (2020). Oxygen Reduction Reactions on Single- or Few-Atom Discrete Active Sites for Heterogeneous Catalysis. Advanced Energy Materials, 10(11), Article ID 1902084.
Open this publication in new window or tab >>Oxygen Reduction Reactions on Single- or Few-Atom Discrete Active Sites for Heterogeneous Catalysis
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2020 (English)In: Advanced Energy Materials, ISSN 1614-6832, E-ISSN 1614-6840, Vol. 10, no 11, article id 1902084Article in journal (Refereed) Published
Abstract [en]

The oxygen reduction reaction (ORR) is of great importance in energy-converting processes such as fuel cells and in metal-air batteries and is vital to facilitate the transition toward a nonfossil dependent society. The ORR has been associated with expensive noble metal catalysts that facilitate the O-2 adsorption, dissociation, and subsequent electron transfer. Single- or few-atom motifs based on earth-abundant transition metals, such as Fe, Co, and Mo, combined with nonmetallic elements, such as P, S, and N, embedded in a carbon-based matrix represent one of the most promising alternatives. Often these are referred to as single atom catalysts; however, the coordination number of the metal atom as well as the type and nearest neighbor configuration has a strong influence on the function of the active sites, and a more adequate term to describe them is metal-coordinated motifs. Despite intense research, their function and catalytic mechanism still puzzle researchers. They are not molecular systems with discrete energy states; neither can they fully be described by theories that are adapted for heterogeneous bulk catalysts. Here, recent results on single- and few-atom electrocatalyst motifs are reviewed with an emphasis on reports discussing the function and the mechanism of the active sites.

Place, publisher, year, edition, pages
John Wiley & Sons, 2020
Keywords
active sites, catalyst motifs, electrocatalysis, oxygen reduction reaction, single active atom catalysts, transition metals, X-ray adsorption spectroscopy
National Category
Other Chemistry Topics Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-164137 (URN)10.1002/aenm.201902084 (DOI)000486795700001 ()2-s2.0-85073921376 (Scopus ID)
Funder
Swedish Research Council, 186-0637Swedish Energy Agency, 45419-1Swedish Research Council, 2018-03937Swedish Research Council, 2017-04862
Available from: 2019-10-17 Created: 2019-10-17 Last updated: 2023-03-24Bibliographically approved
Wu, J., Sharifi, T., Gao, Y., Zhang, T. & Ajayan, P. M. (2019). Emerging Carbon-Based Heterogeneous Catalysts for Electrochemical Reduction of Carbon Dioxide into Value-Added Chemicals. Advanced Materials, 31(13), Article ID 1804257.
Open this publication in new window or tab >>Emerging Carbon-Based Heterogeneous Catalysts for Electrochemical Reduction of Carbon Dioxide into Value-Added Chemicals
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2019 (English)In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 31, no 13, article id 1804257Article, review/survey (Refereed) Published
Abstract [en]

The electrocatalytic reduction of CO2 provides a sustainable way to mitigate CO2 emissions, as well as store intermittent electrical energy into chemicals. However, its slow kinetics and the lack of ability to control the products of the reaction inhibit its industrial applications. In addition, the immature mechanistic understanding of the reduction process makes it difficult to develop a selective, scalable, and stable electrocatalyst. Carbon-based materials are widely considered as a stable and abundant alternative to metals for catalyzing some of the key electrochemical reactions, including the CO2 reduction reaction. In this context, recent research advances in the development of heterogeneous nanostructured carbon-based catalysts for electrochemical reduction of CO2 are summarized. The leading factors for consideration in carbon-based catalyst research are discussed by analyzing the main challenges faced by electrochemical reduction of CO2. Then the emerging metal-free doped carbon and aromatic N-heterocycle catalysts for electrochemical reduction of CO2 with an emphasis on the formation of multicarbon hydrocarbons and oxygenates are discussed. Following that, the recent progress in metal-nitrogen-carbon structures as an extension of carbon-based catalysts is scrutinized. Finally, an outlook for the future development of catalysts as well as the whole electrochemical system for CO2 reduction is provided.

Keywords
aromatic N-heterocycles, carbon, CO2 reduction, heteroatom doping, metal-nitrogen-carbon ructures
National Category
Physical Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-158381 (URN)10.1002/adma.201804257 (DOI)000463970200006 ()30589109 (PubMedID)2-s2.0-85059134052 (Scopus ID)
Available from: 2019-04-29 Created: 2019-04-29 Last updated: 2023-03-23Bibliographically approved
Sharifi, T., Xie, Y., Zhang, X., Barzegar, H. R., Lei, J., Coulter, G., . . . Ajayan, P. M. (2019). Graphene as an electrochemical transfer layer. Carbon, 141, 266-273
Open this publication in new window or tab >>Graphene as an electrochemical transfer layer
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2019 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 141, p. 266-273Article in journal (Refereed) Published
Abstract [en]

The capability of graphene to adopt a property from an adjacent material is investigated by measuring the electrochemical performance of a monolayer graphene placed on top of thin cobalt oxide (Co3O4) nanosheets. In this assembly, monolayer graphene works as an interfacial layer which inhibits the direct contact of the actual electroactive material and electrolyte during electrochemical reaction. The results show that while graphene is electrochemically inert, it behaves as an active material to catalyze oxygen evolution reaction (OER) once placed on top of Co3O4 nanosheets. The graphene-covered Co3O4 model system shows electrochemical performance similar to Co3O4 indicating complete transference of the electrochemical property of the metal oxide to the graphene. Based on density functional theory (DFT) calculations, charge transfer from graphene to Co3O4 is the key factor for turning the electrochemically inactive graphene to an apparent active material. 

Place, publisher, year, edition, pages
Elsevier, 2019
National Category
Materials Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-154021 (URN)10.1016/j.carbon.2018.09.056 (DOI)000450312600029 ()2-s2.0-85056148229 (Scopus ID)
Funder
Swedish Research Council, 2015-06462Swedish Research Council, 2015-00520
Available from: 2018-12-20 Created: 2018-12-20 Last updated: 2023-03-23Bibliographically approved
Swaminathan, J., Puthirath, A. B., Sahoo, M. R., Nayak, S. K., Costin, G., Vajtai, R., . . . Ajayan, P. M. (2019). Tuning the Electrocatalytic Activity of Co3O4 through Discrete Elemental Doping. ACS Applied Materials and Interfaces, 11(43), 39706-39714
Open this publication in new window or tab >>Tuning the Electrocatalytic Activity of Co3O4 through Discrete Elemental Doping
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2019 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 11, no 43, p. 39706-39714Article in journal (Refereed) Published
Abstract [en]

To gain constructive insight into the possible effect of doping on the electrocatalytic activity of materials, a catalytic framework with a discrete distribution of dopants is an appropriate model system. Such a system assures well-defined active centers, maximum atom utilization efficiency, and hence enhanced selectivity, catalytic activity, and stability. Herein, a comprehensive investigation of the electrocatalytic activity of iron-doped cobalt oxide (Fe-Co3O4) nanosheets is presented. In order to understand the contribution of dopants, a series of materials with controlled doping levels are investigated. By controlled iron inclusion into the structure of Co3O4, an apparent improvement in the oxygen evolution reaction activity which is reflected in the decrease of 160 mV in the overpotential to reach the current density of 10 mA/cm(2) is manifested. Additionally, it is shown that there exists an optimum doping content above which the catalytic activity fades. Further investigation of the system with density functional calculations reveals that, along with the optimization of adsorption energy toward the reaction intermediates, substantial downshift of the Fermi level and delocalization of electron density occurs on introducing iron ions into the structure.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
Keywords
oxygen evolution reaction, doping, cobalt oxide, iron-doped cobalt oxide
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-165337 (URN)10.1021/acsami.9b06815 (DOI)000493869700027 ()31595745 (PubMedID)2-s2.0-85074198045 (Scopus ID)
Funder
Swedish Research Council, 2015-06462
Available from: 2019-11-26 Created: 2019-11-26 Last updated: 2023-03-24Bibliographically approved
Liu, Y., Liang, C., Wu, J., Sharifi, T., Xu, H., Nakanishi, Y., . . . Ajayan, P. M. (2018). Atomic layered titanium sulfide quantum dots as electrocatalysts for enhanced hydrogen evolution reaction. Advanced Materials Interfaces, 5(1), Article ID 1700895.
Open this publication in new window or tab >>Atomic layered titanium sulfide quantum dots as electrocatalysts for enhanced hydrogen evolution reaction
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2018 (English)In: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 5, no 1, article id 1700895Article in journal (Refereed) Published
Abstract [en]

The overall electrocatalytic activity toward hydrogen evolution reaction for layered transition metal dichalcogenides is governed by their intrinsic activity, the corresponding density of active sites, and the electron transfer resistance. Here, nanoengineering strategies to scale down both the lateral size and thickness of layered 1T-TiS2 powder to quantum dots (QDs) by bath sonication and probing sonication incision are employed. Uniform lateral size of 3-6 nm in the resulting QDs enhances the density of edge sites while the atomic layer thickness (1-2 nm) facilitates the electron transfer from the substrate to the edge sites. The obtained TiS2 QDs exhibit superior hydrogen evolution reaction activity over TiS2 nanosheets and MoS2 QDs prepared by the same method. The turnover frequency of TiS2 QDs with a small loading of 0.7 ng cm(-2) in an optimal deposition on electrode reached approximate to 2.0 s(-1) at an overpotential of -0.2 V versus RHE, several orders of magnitude higher than TiS2 nanosheets (0.01 s(-1)) and MoS2 QDs (0.07 s(-1)).

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
Keywords
atomic layer, electrocatalysis, hydrogen evolution reaction, quantum dots, transition metal chalcogenides
National Category
Materials Chemistry Physical Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-144396 (URN)10.1002/admi.201700895 (DOI)000419675700010 ()2-s2.0-85032265264 (Scopus ID)
Available from: 2018-02-13 Created: 2018-02-13 Last updated: 2023-03-24Bibliographically approved
Sandström, R., Ekspong, J., Annamalai, A., Sharifi, T., Klechikov, A. & Wågberg, T. (2018). Fabrication of microporous layer - free hierarchical gas diffusion electrode as a low Pt-loading PEMFC cathode by direct growth of helical carbon nanofibers. RSC Advances, 8(72), 41566-41574
Open this publication in new window or tab >>Fabrication of microporous layer - free hierarchical gas diffusion electrode as a low Pt-loading PEMFC cathode by direct growth of helical carbon nanofibers
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2018 (English)In: RSC Advances, E-ISSN 2046-2069, Vol. 8, no 72, p. 41566-41574Article in journal (Refereed) Published
Abstract [en]

Improving interfacial contact between each component in the proton exchange membrane fuel cell (PEMFC) can lead to a significant increase in power density and Pt utilization. In this work, the junction between the catalyst layer and gas diffusion layer (GDL) is greatly enhanced through direct attachment of helical carbon nanofibers, giving rise to a hierarchical structure within the electrical interconnections. The alternative novel GDL is produced by spraying a thin layer of Pd2C60 precursor on commercial carbon paper, followed by chemical vapor deposition growth resulting in a surface morphology of well-attached nanofibers surrounding the microfibers present in the commercial carbon paper. Subsequent solvothermal deposition of platinum nanoparticles allowed evaluation of its suitability as gas diffusion electrode in cathodic H-2/O-2 PEMFC environment. A combination of lowered charge transfer resistance and enhanced Pt-utilization is attributed to its unique wire-like appearance and its robust properties. The fabricated microporous layer - free GDL is suitable for relatively aggressive membrane electrode assembly fabrication procedures and is produced by industrially favorable techniques, rendering it capable of efficiently supporting small amounts of precious metal catalyst nanoparticles in various PEM applications.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2018
National Category
Materials Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-155124 (URN)10.1039/c8ra07569g (DOI)000453914300053 ()2-s2.0-85058569317 (Scopus ID)
Funder
The Kempe FoundationsSwedish Energy AgencySwedish Research Council
Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2023-03-23Bibliographically approved
Sharifi, T., Yazdi, S., Costin, G., Apte, A., Coulter, G., Tiwary, C. & Ajayan, P. M. (2018). Impurity-Controlled Crystal Growth in Low-Dimensional Bismuth Telluride. Chemistry of Materials, 30(17), 6108-6115
Open this publication in new window or tab >>Impurity-Controlled Crystal Growth in Low-Dimensional Bismuth Telluride
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2018 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 30, no 17, p. 6108-6115Article in journal (Refereed) Published
Abstract [en]

Topological insulators, such as layered Bi2Te3, exhibit extraordinary properties, manifesting profoundly only at nanoscale thicknesses. However, it has been challenging to synthesize these structures with controlled thicknesses. Here, control over the thickness of solvothermally grown Bi2Te3 nanosheets is demonstrated by manipulating the crystal growth through select and controlled impurity atom addition. By a comprehensive analysis of the growth mechanism and intentional addition of Fe impurity, we demonstrate that the nucleation and growth of few-layer nanosheets of Bi2Te3 can be stabilized in solution. Via optimization of the Fe concentration, nanosheets thinner than 6 nm, and as thin as 2 nm, can be synthesized. Such thicknesses are smaller than the anticipated critical thickness for the transition of topological insulators to the quantum spin Hall regime.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
National Category
Materials Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-152406 (URN)10.1021/acs.chemmater.8b02548 (DOI)000444792800035 ()2-s2.0-85052320151 (Scopus ID)
Funder
Swedish Research Council, 2015-06462
Available from: 2018-10-05 Created: 2018-10-05 Last updated: 2023-03-24Bibliographically approved
Ngoc Pham, T., Sharifi, T., Sandström, R., Siljebo, W., Shchukarev, A., Kordas, K., . . . Mikkola, J.-P. (2017). Robust hierarchical 3D carbon foam electrode for efficient water electrolysis. Scientific Reports, 7, Article ID 6112.
Open this publication in new window or tab >>Robust hierarchical 3D carbon foam electrode for efficient water electrolysis
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2017 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 7, article id 6112Article in journal (Refereed) Published
Abstract [en]

Herein we report a 3D heterostructure comprising a hierarchical macroporous carbon foam that incorporates mesoporous carbon nanotubes decorated with cobalt oxide nanoparticles as an unique and highly efficient electrode material for the oxygen evolution reaction (OER) in electrocatalytic water splitting. The best performing electrode material showed high stability after 10 h, at constant potential of 1.7 V vs. RHE (reversible hydrogen electrode) in a 0.1 M KOH solution and high electrocatalytic activity in OER with low overpotential (0.38 V vs RHE at 10 mA cm(-2)). The excellent electrocatalytic performance of the electrode is rationalized by the overall 3D macroporous structure and with the firmly integrated CNTs directly grown on the foam, resulting in a large specific surface area, good electrical conductivity, as well as an efficient electrolyte transport into the whole electrode matrix concurrent with an ability to quickly dispose oxygen bubbles into the electrolyte. The eminent properties of the three-dimensional structured carbon matrix, which can be synthesized through a simple, scalable and cost effective pyrolysis process show that it has potential to be implemented in large-scale water electrolysis systems.

Place, publisher, year, edition, pages
Nature Publishing Group, 2017
National Category
Inorganic Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-127042 (URN)10.1038/s41598-017-05215-1 (DOI)000406285700020 ()28733585 (PubMedID)2-s2.0-85025588386 (Scopus ID)
Projects
Bio4Energy
Funder
Bio4Energy
Available from: 2016-10-26 Created: 2016-10-26 Last updated: 2022-09-15Bibliographically approved
Sharifi, T., Zhang, X., Costin, G., Yazdi, S., Woellner, C. F., Liu, Y., . . . Ajayan, P. (2017). Thermoelectricity Enhanced Electrocatalysis. Nano Letters, 17(12), 7908-7913
Open this publication in new window or tab >>Thermoelectricity Enhanced Electrocatalysis
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2017 (English)In: Nano Letters, ISSN 1530-6984, E-ISSN 1530-6992, Vol. 17, no 12, p. 7908-7913Article in journal (Refereed) Published
Abstract [en]

We show that thermoelectric materials can function as electrocatalysts and use thermoelectric voltage generated to initiate and boost electrocatalytic reactions. The electrocatalytic activity is promoted by the use of nanostructured thermoelectric materials in a hydrogen evolution reaction (HER) by the thermoelectricity generated from induced temperature gradients. This phenomenon is demonstrated using two-dimensional layered thermoelectric materials Sb2Te3 and Bi0.5Sb1.5Te3 where a current density approaching ∼50 mA/cm2 is produced at zero potential for Bi0.5Sb1.5Te3 in the presence of a temperature gradient of 90 °C. In addition, the turnover frequency reaches to 2.7 s–1 at 100 mV under this condition which was zero in the absence of temperature gradient. This result adds a new dimension to the properties of thermoelectric materials which has not been explored before and can be applied in the field of electrocatalysis and energy generation.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
Keywords
Thermoelectrocatalysis, thermoelectric materials, electrocatalysis, temperature gradient, hydrogen olution reaction
National Category
Other Materials Engineering Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-143944 (URN)10.1021/acs.nanolett.7b04244 (DOI)000418393300102 ()29116809 (PubMedID)2-s2.0-85038213982 (Scopus ID)
Available from: 2018-01-15 Created: 2018-01-15 Last updated: 2023-03-23Bibliographically approved
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