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Stabilizing Active Edge Sites in Semicrystalline Molybdenum Sulfide by Anchorage on Nitrogen-Doped Carbon Nanotubes for Hydrogen Evolution Reaction
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
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2016 (Engelska)Ingår i: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 26, nr 37, s. 6766-6776Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Finding an abundant and cost-effective electrocatalyst for the hydrogen evolu-tion reaction (HER) is crucial for a global production of hydrogen from water electrolysis. This work reports an exceptionally large surface area hybrid catalyst electrode comprising semicrystalline molybdenum sulfi de (MoS 2+ x) catalystattached on a substrate based on nitrogen-doped carbon nanotubes (N-CNTs), which are directly grown on carbon fiber paper (CP). It is shown here that nitrogen-doping of the carbon nanotubes improves the anchoring of MoS 2+ xcatalyst compared to undoped carbon nanotubes and concurrently stabilizes a semicrystalline structure of MoS 2+ x with a high exposure of active sites for HER. The well-connected constituents of the hybrid catalyst are shown to facilitate electron transport and as a result of the good attributes, the MoS 2+ x/N-CNT/CPelectrode exhibits an onset potential of −135 mV for HER in 0.5 M H2SO4, a Tafel slope of 36 mV dec −1, and high stability at a current density of −10 mA cm −2.

Ort, förlag, år, upplaga, sidor
Wiley-VCH Verlagsgesellschaft, 2016. Vol. 26, nr 37, s. 6766-6776
Nyckelord [en]
carbon paper, hydrogen evolution reaction, molybdenum disulfide—MoS2, nitrogen doped carbon nanotubes, water splitting catalysts
Nationell ämneskategori
Oorganisk kemi Annan kemiteknik Den kondenserade materiens fysik
Identifikatorer
URN: urn:nbn:se:umu:diva-128753DOI: 10.1002/adfm.201601994ISI: 000384810300006Scopus ID: 2-s2.0-84979085766OAI: oai:DiVA.org:umu-128753DiVA, id: diva2:1056159
Tillgänglig från: 2016-12-14 Skapad: 2016-12-14 Senast uppdaterad: 2023-03-23Bibliografiskt granskad
Ingår i avhandling
1. Electrocatalysts for sustainable hydrogen energy: disordered and heterogeneous nanomaterials
Öppna denna publikation i ny flik eller fönster >>Electrocatalysts for sustainable hydrogen energy: disordered and heterogeneous nanomaterials
2021 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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. 

Ort, förlag, år, upplaga, sidor
Umeå: Umeå Universitet, 2021. s. 88
Nyckelord
Water splitting, Electrochemistry, Nanomaterials, Density functional theory, Hydrogen evolution, MoS2, Fuel cell
Nationell ämneskategori
Den kondenserade materiens fysik
Forskningsämne
nanomaterial; fysik; fysikalisk kemi
Identifikatorer
urn:nbn:se:umu:diva-180130 (URN)978-91-7855-482-9 (ISBN)978-91-7855-481-2 (ISBN)
Disputation
2021-03-11, BIO.A.206 – Aula Anatomica, Umeå, 09:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2021-02-18 Skapad: 2021-02-15 Senast uppdaterad: 2021-02-16Bibliografiskt granskad

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Ekspong, JoakimSharifi, TivaShchukarev, AndreyKlechikov, AlexeyWågberg, ThomasGracia-Espino, Eduardo

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Ekspong, JoakimSharifi, TivaShchukarev, AndreyKlechikov, AlexeyWågberg, ThomasGracia-Espino, Eduardo
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