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Temperature dependent intercalation of molten 1-hexadecanol into Brodie graphite oxide
Umeå University, Faculty of Science and Technology, Department of Physics.ORCID iD: 0000-0002-8438-2581
Umeå University, Faculty of Science and Technology, Department of Physics.ORCID iD: 0000-0002-1535-9476
Umeå University, Faculty of Science and Technology, Department of Physics.ORCID iD: 0000-0002-3881-6764
Umeå University, Faculty of Science and Technology, Department of Physics.
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2023 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 203, p. 770-784Article in journal (Refereed) Published
Abstract [en]

Intercalation of very long molecules into the structure of multi-layered graphene oxide (GO) was studied using example of 1-hexadecanol (C16), an alcohol molecule with 16 carbon atoms. Brodie graphite oxide (BGO) immersed in excess of liquid C16 just above the melting point shows expansion of c-unit cell parameter from ∼6 Å to ∼48.76 Å forming a structure with two densely packed layers of C16 molecules in a perpendicular orientation relative to the GO planes (α-phase). Heating of the BGO-C16 α-phase in excess of C16 melt results in reversible phase transition into β-phase at 336–342K. The β-phase shows much smaller unit cell parameter of 29.83 Å (363K). Analysis of data obtained using vacuum-driven evaporation of C16 from the β-phase provides evidence for structure of β-phase consisting of five layers of C16 molecules in parallel to GO plane orientation. Therefore, the transition from α-to β-phase corresponds to change in orientation C16 molecules from perpendicular to parallel relative to GO planes and decrease in the amount of intercalated solvent. Cooling of the β-phase in absence of C16 melt is found to result in the formation of γ-phase with inter-layer distance of ∼26.5 Å corresponding to one layer of C16 molecules intercalated perpendicularly relative to the GO planes. Structures with one and two layers of C16 molecules parallel to GO planes were identified in samples with rather small initial loading of C16. Surprisingly rich variety of structures revealed in the BGO-C16 system provides opportunities to create materials with precisely controlled GO inter-layer distance.

Place, publisher, year, edition, pages
Elsevier, 2023. Vol. 203, p. 770-784
Keywords [en]
Graphene oxide, Graphite oxide, Intercalation, Phase transition, Swelling
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:umu:diva-201949DOI: 10.1016/j.carbon.2022.12.030ISI: 000906322600001Scopus ID: 2-s2.0-85143963156OAI: oai:DiVA.org:umu-201949DiVA, id: diva2:1722412
Funder
EU, Horizon 2020, 881603Swedish Energy Agency, 50620-1Swedish Research Council, 2018-07152Vinnova, 2018-04969Swedish Research Council Formas, 2019-02496Available from: 2022-12-29 Created: 2022-12-29 Last updated: 2023-09-05Bibliographically approved
In thesis
1. Properties and applications of materials based on graphite oxide
Open this publication in new window or tab >>Properties and applications of materials based on graphite oxide
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Egenskaper och tillämpningar av material baserade på grafitoxid
Abstract [en]

Graphite oxide (GO) is a hydrophilic, layered material prepared by oxidation of graphite. In the first part of this thesis, we studied materials produced from GO by intercalation and functionalization. The second part of the thesis was focused on supercapacitor applications of high surface area carbons prepared from GO using chemical activation. 

A detailed study of acetylated GO (AcGO) was performed to verify structure and properties of this material. Reports from 1960’s suggested that AcGO has “pillared” structure. Our analysis showed that the AcGO demonstrates expanded structure due to acetylation but exhibits negligible specific surface area and should not be considered as a pillared material. 

Pillared reduced GO (prGO) was prepared by applying mild annealing to GO material pillared with tetrapod-shaped amine molecules. PrGO showed relatively high surface area due to remaining pillaring molecules in the structure. The prGO is hydrophobic and exhibits 100x improved conductivity compared to precursor. PrGO is one of few true pillared structures reported in literature so far, and the first ever prepared starting from pillared GO.

We also investigated the sorption of common dyes, methylene blue (MB), rose bengal (RB) and crystal violet (CV), by multilayered graphene oxide materials. We found that MB dissolved in ethanol intercalates the GO structure, as evidenced by significant expansion of inter-layer distance, and increase in weight due to sorption. In contrast to MB, GO is not easily intercalated by CV and RB dyes. We believe that the flat MB molecule shape allows easier insertion between GO layers compared to twisted and non-flat CV and RB molecules. Our results suggest that penetration into GO inter-layers depends not only on the size of molecules, but also on the shape.

Temperature dependent study of structures formed by Brodie GO (BGO) in liquid alkyl alcohols was performed for a set starting from undecyl alcohol (no. of C=11) and up to behenyl alcohol (no. of C=22). We found that BGO exhibits strong swelling in all molten alcohols in this set. Heating just above the melting point of alcohol results in expansion of inter-layer distance of GO due to intercalation of two layers of alcohol molecules in orientation perpendicular to graphene oxide planes (α-phase). Further heating of α-phase results in incongruent melting and formation of new phase with significantly smaller inter-layer distance and amount of intercalated alcohol (β-phase). The transition from α-to β-phase is distinctly different compared to swelling transitions previously observed for BGO in smaller alcohols (no. of C<10). A more detailed study of the BGO-C16 system revealed that β-phase has structure with alcohol molecules forming layers mostly in parallel to graphene oxide orientation.

In the second part of this thesis we studied activated reduced GO (a-rGO) as electrode material in supercapacitors. A-rGO is a high surface material (~3000 m2g-1) obtained by KOH activation of rGO. We developed formulations for stable aqueous dispersions of a-rGO optimized for preparation of electrodes by semi-industrial spray-gun deposition. The electrodes prepared by spray deposition showed energy storage parameters only slightly lower compared to lab scale blade-deposited electrodes. Spray-gun deposition might provide significant advantage for industry over conventional methods to prepare electrodes from a-rGO. 

We also applied KOH activation procedure, optimized for producing high surface area a-rGO, to biochar prepared from pine cones. Using this cost free “waste” picked up in Umeå region forest we produced high quality activated carbon very similar to a-rGO in terms of structure, pore size and surface area. Overall, the energy storage parameters of electrodes prepared using the activated carbon from pine cones were on the same level as a-rGO electrodes, which are produced by a lot more complex and expensive chemical treatments.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2023. p. 86
Keywords
Graphene, Graphite Oxide, Graphene Oxide, Swelling, Phase Transition, Intercalation, Activated Graphene, Activated Carbon, Supercapacitors, Neutron Reflectometry
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-214116 (URN)978-91-8070-102-0 (ISBN)978-91-8070-103-7 (ISBN)
Public defence
2023-09-29, NAT.D.480, Naturvetarhuset, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2023-09-08 Created: 2023-09-05 Last updated: 2023-09-05Bibliographically approved

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Nordenström, AndreasIakunkov, ArtemBoulanger, NicolasLi, GuiTalyzin, Aleksander V.

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