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Stable Sulfur‐Intercalated 1T′ MoS2 on Graphitic Nanoribbons as Hydrogen Evolution Electrocatalyst
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics.
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2018 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 28, no 46, article id 1802744Article in journal (Refereed) Published
Abstract [en]

The metastable 1T′ polymorph of molybdenum disulfide (MoS2) has shown excellent catalytic activity toward the hydrogen evolution reaction (HER) in water‐splitting applications. Its basal plane exhibits high catalytic activity comparable to the edges in 2H MoS2 and noble metal platinum. However, the production and application of this polymorph are limited by its lower energetic stability compared to the semiconducting 2H MoS2 phase. Here, the production of stable intercalated 1T′ MoS2 nanosheets attached on graphitic nanoribbons is reported. The intercalated 1T′ MoS2 exhibits a stoichiometric S:Mo ratio of 2.3 (±0.1):1 with an expanded interlayer distance of 10 Å caused by a sulfur‐rich intercalation agent and is stable at room temperature for several months even after drying. The composition, structure, and catalytic activity toward HER are investigated both experimentally and theoretically. It is concluded that the 1T′ MoS2 phase is stabilized by the intercalated agents, which further improves the basal planes′ catalytic activity toward HER.

Place, publisher, year, edition, pages
WILEY-VCH VERLAG GMBH , 2018. Vol. 28, no 46, article id 1802744
Keywords [en]
DFT calculations, hydrogen evolution reaction, intercalation, MoS2, transition metal chalcogenides
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:umu:diva-154948DOI: 10.1002/adfm.201802744ISI: 000449887300019Scopus ID: 2-s2.0-85054188827OAI: oai:DiVA.org:umu-154948DiVA, id: diva2:1275999
Available from: 2019-01-07 Created: 2019-01-07 Last updated: 2023-03-23Bibliographically approved
In thesis
1. Electrocatalysts for sustainable hydrogen energy: disordered and heterogeneous nanomaterials
Open this publication in new window or tab >>Electrocatalysts for sustainable hydrogen energy: disordered and heterogeneous nanomaterials
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

With the current global greenhouse gas emissions, our remaining carbon budget is depleted in only 7 years. After that, several biophysical systems are predicted to collapse such as the arctic ice, coral reefs and the permafrost, leading to potentially irreversible consequences. Our emissions are strongly correlated to access of energy and even if we are aware of the planetary emergency today, our emissions still continue to grow. Electrical vehicles have the possibility to reduce the emissions in the transportation sector significantly. However, these vehicles are still expensive and impractical for long-distance or heavy transportation. While political actions and technological development are essential to keep prices down, the driving dis- tance can be increased by replacing the batteries for onboard electricity production. 

In hydrogen fuel cells, electricity is produced by combining hydrogen gas (H2) and oxygen with only water as the by-product and if employed in electrical vehicles, distances of 500 km are enabled with a refueling time in 5 minutes. For other uses than in vehicles, H2 is also promising for large-scale electricity storage and for several industrial processes such as manufacturing CO2-free steel, ammonia and synthetic fuels. However, today most H2 production methods relies on fossil fuels and releases huge amounts of CO2. 

Electrolysis of water is an alternative production method where H2, along with oxygen are produced from water. To split the water, electricity has to be added and if renewable energy sources are used, the method has zero emissions and is considered most promising for a sustainable hydrogen energy economy. The tech- nique is relatively expensive compared to the fossil fuel-based methods and relies on rare noble metals such as platinum as catalysts for decreasing the required energy to split water. For large scale productions, these metals need to be replaced by more sustainable and abundant catalysts to lower the cost and minimize the environmental impacts. 

In this thesis we have investigated such candidates for the water splitting reaction but also to some extent for the oxygen reduction reaction in fuel cells. By combining theory and experiments we hope to aid in the development and facilitate a transition to clean hydrogen energy. We find among other things that i) defects in catalytic materials plays a significant role the performance and efficiency, and that ii) heterogeneity influence the adsorption energies of reaction intermediates and hence the catalytic efficiency and iii) while defects are not often studied for electrocatalytic reactions, these may inspire for novel materials in the future. 

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2021. p. 88
Keywords
Water splitting, Electrochemistry, Nanomaterials, Density functional theory, Hydrogen evolution, MoS2, Fuel cell
National Category
Condensed Matter Physics
Research subject
nanomaterials; Physics; Physical Chemistry
Identifiers
urn:nbn:se:umu:diva-180130 (URN)978-91-7855-482-9 (ISBN)978-91-7855-481-2 (ISBN)
Public defence
2021-03-11, BIO.A.206 – Aula Anatomica, Umeå, 09:00 (English)
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Supervisors
Available from: 2021-02-18 Created: 2021-02-15 Last updated: 2021-02-16Bibliographically approved

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Ekspong, JoakimSandström, RobinWågberg, ThomasGracia-Espino, Eduardo

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