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Sharifi, Tiva
Publications (10 of 29) Show all publications
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
Identifiers
urn:nbn:se:umu:diva-158381 (URN)10.1002/adma.201804257 (DOI)000463970200006 ()30589109 (PubMedID)
Available from: 2019-04-29 Created: 2019-04-29 Last updated: 2019-04-29Bibliographically 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
Identifiers
urn:nbn:se:umu:diva-154021 (URN)10.1016/j.carbon.2018.09.056 (DOI)000450312600029 ()
Funder
Swedish Research Council, 2015-06462Swedish Research Council, 2015-00520
Available from: 2018-12-20 Created: 2018-12-20 Last updated: 2018-12-20Bibliographically approved
Sharifi, T., Gracia-Espino, E., Chen, A., Hu, G. & Wågberg, T. (2019). Oxygen Reduction Reactions on Single- or Few-Atom Discrete Active Sites for Heterogeneous Catalysis. Advanced Energy Materials, 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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2019 (English)In: Advanced Energy Materials, ISSN 1614-6832, article id 1902084Article in journal (Refereed) Epub ahead of print
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
WILEY-V C H VERLAG GMBH, 2019
Keywords
active sites, catalyst motifs, electrocatalysis, oxygen reduction reaction, single active atom catalysts, transition metals, X-ray adsorption spectroscopy
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:umu:diva-164137 (URN)10.1002/aenm.201902084 (DOI)000486795700001 ()
Available from: 2019-10-17 Created: 2019-10-17 Last updated: 2019-10-17
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
Identifiers
urn:nbn:se:umu:diva-144396 (URN)10.1002/admi.201700895 (DOI)000419675700010 ()
Available from: 2018-02-13 Created: 2018-02-13 Last updated: 2018-06-09Bibliographically 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, ISSN 2046-2069, 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
Identifiers
urn:nbn:se:umu:diva-155124 (URN)10.1039/c8ra07569g (DOI)000453914300053 ()
Funder
The Kempe FoundationsSwedish Energy AgencySwedish Research Council
Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2019-04-29Bibliographically 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 ()
Funder
Swedish Research Council, 2015-06462
Available from: 2018-10-05 Created: 2018-10-05 Last updated: 2018-10-05Bibliographically 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, ISSN 2045-2322, 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.

National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:umu:diva-127042 (URN)10.1038/s41598-017-05215-1 (DOI)000406285700020 ()28733585 (PubMedID)
Projects
Bio4Energy
Available from: 2016-10-26 Created: 2016-10-26 Last updated: 2019-08-30Bibliographically approved
Sharifi, T., Zhang, X., Costin, G., Yazdi, S., Woellner, C. F., Liu, Y., . . . Ajayan, P. (2017). Thermoelectricity Enhanced Electrocatalysis. Nano letters (Print), 17(12), 7908-7913
Open this publication in new window or tab >>Thermoelectricity Enhanced Electrocatalysis
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2017 (English)In: Nano letters (Print), 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
Identifiers
urn:nbn:se:umu:diva-143944 (URN)10.1021/acs.nanolett.7b04244 (DOI)000418393300102 ()29116809 (PubMedID)
Available from: 2018-01-15 Created: 2018-01-15 Last updated: 2018-06-09Bibliographically approved
Hu, G., Gracia-Espino, E., Sandström, R., Sharifi, T., Cheng, S., Shen, H., . . . Wågberg, T. (2016). Atomistic understanding of the origin of high oxygen reduction electrocatalytic activity of cuboctahedral Pt3Co-Pt core-shell nanoparticles. Catalysis Science & Technology, 6(5), 1393-1401
Open this publication in new window or tab >>Atomistic understanding of the origin of high oxygen reduction electrocatalytic activity of cuboctahedral Pt3Co-Pt core-shell nanoparticles
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2016 (English)In: Catalysis Science & Technology, ISSN 2044-4753, E-ISSN 2044-4761, Vol. 6, no 5, p. 1393-1401Article in journal (Refereed) Published
Abstract [en]

PtM-based core-shell nanoparticles are a new class of active and stable nanocatalysts for promoting oxygen reduction reaction (ORR); however, the understanding of their high electrocatalytic performance for ORR at the atomistic level is still a great challenge. Herein, we report the synthesis of highly ordered and homogeneous truncated cuboctahedral Pt3Co-Pt core-shell nanoparticles (cs-Pt3Co). By combining atomic resolution electron microscopy, X-ray photoelectron spectroscopy, extensive first-principles calculations, and many other characterization techniques, we conclude that the cs-Pt3Co nanoparticles are composed of a complete or nearly complete Pt monolayer skin, followed by a secondary shell containing 5-6 layers with similar to 78 at% of Pt, in a Pt3Co configuration, and finally a Co-rich core with 64 at% of Pt. Only this particular structure is consistent with the very high electrocatalytic activity of cs-Pt3Co nanoparticles for ORR, which is about 6 times higher than commercial 30%-Pt/Vulcan and 5 times more active than non-faceted (spherical) alloy Pt3Co nanoparticles. Our study gives an important insight into the atomistic design and understanding of advanced bimetallic nanoparticles for ORR catalysis and other important industrial catalytic applications.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:umu:diva-118998 (URN)10.1039/c5cy01128k (DOI)000371607600014 ()
Available from: 2016-05-03 Created: 2016-04-07 Last updated: 2018-06-07Bibliographically approved
Sharifi, T., Kwong, W. L., Berends, H.-M., Larsen, C., Messinger, J. & Wågberg, T. (2016). Maghemite nanorods anchored on a 3D nitrogen-doped carbon nanotubes substrate as scalable direct electrode for water oxidation. International journal of hydrogen energy, 41(1), 69-78
Open this publication in new window or tab >>Maghemite nanorods anchored on a 3D nitrogen-doped carbon nanotubes substrate as scalable direct electrode for water oxidation
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2016 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 41, no 1, p. 69-78Article in journal (Refereed) Published
Abstract [en]

A hybrid catalyst 3D electrode for electrochemical water oxidation to molecular oxygen is presented. The electrode comprises needle shaped maghemite nanorods firmly anchored to nitrogen doped carbon nanotubes, which in turn are grown on a conducting carbon paper that acts as efficient current collector. In 0.1 M KOH this hybrid electrode reaches a current density of 1 mA/cm(2) (geometric surface) at an overpotential of 362 mV performing high chronoamperometric stability. The electrochemical attributes point toward efficient catalytic processes at the surface of the maghemite nanorods, and demonstrate a very high surface area of the 3D electrode, as well as a firm anchoring of each active component enabling an efficient charge transport from the surface of the maghemite rods to the carbon paper current collector. The latter property also explains the good stability of our hybrid electrode compared to transition metal oxides deposited on conducting support such as fluorine doped tin oxide. These results introduce maghemite as efficient, stable and earth abundant oxygen evolution reaction catalyst, and provide insight into key issues for obtaining practical electrodes for oxygen evolution reaction, which are compatible with large scale production processes. 

Keywords
Nitrogen-doped carbon nanotubes, Maghemite, Hybrid catalyst, Water oxidation, 3D electrode
National Category
Materials Chemistry Other Chemistry Topics Other Chemical Engineering
Identifiers
urn:nbn:se:umu:diva-130009 (URN)10.1016/j.ijhydene.2015.11.165 (DOI)000368955300005 ()
Available from: 2017-01-11 Created: 2017-01-11 Last updated: 2018-06-09Bibliographically approved
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