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Maghemite nanorods anchored on a 3D nitrogen-doped carbon nanotubes substrate as scalable direct electrode for water oxidation
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Chemistry.ORCID iD: 0000-0002-9732-8867
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Umeå University, Faculty of Science and Technology, Department of Physics.
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2016 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 41, no 1, 69-78 p.Article 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. 

Place, publisher, year, edition, pages
2016. Vol. 41, no 1, 69-78 p.
Keyword [en]
Nitrogen-doped carbon nanotubes, Maghemite, Hybrid catalyst, Water oxidation, 3D electrode
National Category
Materials Chemistry Other Chemistry Topics Other Chemical Engineering
Identifiers
URN: urn:nbn:se:umu:diva-130009DOI: 10.1016/j.ijhydene.2015.11.165ISI: 000368955300005OAI: oai:DiVA.org:umu-130009DiVA: diva2:1063895
Available from: 2017-01-11 Created: 2017-01-11 Last updated: 2017-03-21Bibliographically approved
In thesis
1. Efficient electrocatalysts based on nitrrogen-doped carbon nanostructures for energy applications
Open this publication in new window or tab >>Efficient electrocatalysts based on nitrrogen-doped carbon nanostructures for energy applications
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Carbon nanostructures have emerged as a key material in nanotechnology and continuously find new areas of applications. Particularly, they are attractive due to their excellent properties as support for catalyst nanostructures leading to highly efficient composite materials for various electrochemical applications. The interest in these structures is further increased by the possibility to alter their electronic and structural properties by various methods. Heteroatom doping of carbon nanostructures is one of the approaches which may induce intrinsic catalytic activity in these materials. In addition, such introduction of guest elements into the hexagonal carbon skeleton provides strong nucleation sites which facilitate the stabilization of nanostructures on their surface. In this thesis we present detailed studies on the nitrogen incorporation into carbon nanostructures, particularly carbon nanotubes and reduced graphene oxide. Due to the high impact of nitrogen configuration on the intrinsic electrocatalytic properties of carbon nanostructures, we investigated the nitrogen functionalities using X-ray photoelectron spectroscopy and Raman spectroscopy. Based on our achievements we could assign the most electrocatalytic active nitrogen site in nitrogen-doped carbon nanotubes (NCNTs) for catalytic oxygen reduction reaction (ORR) which is an important reaction in energy conversion systems such as fuel cells. We then used nitrogen-doped carbon nanostructures as a key component to manufacture hybrid material, where the nitrogen doped nanostructures has a role of both stabilizing the nanostructures and to work as conductive additive to assist the charge transfer from the other constituents suffering from inherently poor conductivity. Our hybrid material comprising transition metal oxides (Fe2O3 and Co3O4) anchored on nitrogen-doped carbon nanostructure were used to both manufacture an exotic type of graphene nanoscrolls, as well as studied and evaluated as an electrocatalyst in various electrochemical reactions. We show that the self-assembled electrodes exhibited better performance and higher stability compared to when the same material was loaded on common current collectors such as fluorine tin oxide (FTO) coated glass and glassy carbon electrode, with both higher current densities, more efficient charge transfer and lower overpotentials for oxygen evolution and hydrogen evolution reactions, the two important processes in a water splitting device. Our NCNTs-based electrodes showed further excellent performance in lithium ion batteries with high cyclability and capacity. The thesis gives insight into processes, materials, and methods that can be utilized to manufacture an efficient water splitting device, based on earth-abundant self-assembled materials. It further represents a significant advancement of the role of nitrogen in heteroatom-doped nanostructures, both regarding their intrinsic catalytic activity, as well as their role for stabilizing nanostructures.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2015. 76 p.
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:umu:diva-100676 (URN)978-91-7601-214-7 (ISBN)
Public defence
2015-03-31, Naturvetarhuset, N420, Umeå University, Umeå, 13:00 (English)
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Supervisors
Available from: 2015-03-10 Created: 2015-03-06 Last updated: 2017-03-21Bibliographically approved

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Sharifi, TivaKwong, Wai LingBerends, Hans-MartinLarsen, ChristianMessinger, JohannesWågberg, Thomas
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