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Nitrogen-doped Reduced Graphene Oxide Hydrogel Achieved via a One-Step Hydrothermal Process
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, Shenyang 110016, Liaoning, Peoples R China.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
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2019 (English)In: CHEMNANOMAT, ISSN 2199-692X, Vol. 5, no 9, p. 1144-1151Article in journal (Refereed) Published
Abstract [en]

We report an efficient one-step method to achieve highly reduced graphene oxide (rGO) hydrogel doped with nitrogen where the rGO sheets are interconnected forming a porous structure by means of hydrothermal process. During the synthesis, ammonium formate is used as reducing reagent and simultaneously as nitrogen supplier, which delivers nitrogen-doped rGO (NRGO) hydrogel that exhibits C/O atomic ratio as high as at ~11.1 and contains decent ~5.4 at.% nitrogen. As comparison, the reduction efficiency is only half of the value and no nitrogen doping can be obtained when L-ascorbic acid is used as reducing reagent. The resultant NRGO shows enhanced electrocatalytic ability for oxygen reduced reaction indicating its great potential of the one-step method for the catalyst and energy applications. 

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH , 2019. Vol. 5, no 9, p. 1144-1151
Keywords [en]
reduced graphene oxide, ammonium formate, hydrothermal, reduction, oxygen reduction reaction
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Electronics
Identifiers
URN: urn:nbn:se:uu:diva-377624DOI: 10.1002/cnma.201900167ISI: 000476035600001OAI: oai:DiVA.org:uu-377624DiVA, id: diva2:1291198
Funder
Swedish Foundation for Strategic Research , Dnr SE13-0061Swedish Research Council, 621-2014-5596Available from: 2019-02-22 Created: 2019-02-22 Last updated: 2019-11-04Bibliographically approved
In thesis
1. Graphene Based Inks for Printed Electronics
Open this publication in new window or tab >>Graphene Based Inks for Printed Electronics
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The outstanding properties of graphene make it attractive ink filler for conductive inks which plays an important role in printed electronics. This thesis focuses on the ink formulation based on graphene and graphene oxide (GO).

Liquid phase exfoliation of graphite is employed to prepare graphene dispersions, i.e., shear- and electrochemical exfoliation. High concentration graphene dispersions with small size, few-layer graphene platelets are obtained by both methods. With the addition of ethyl cellulose stabilizer, shear-exfoliated graphene platelets in NMP were successfully inkjet printed on different substrates. The printed graphene film with electrical conductivity of ~3^104 S/m was obtained after annealing at 350 °C for one hour. Alternatively, the electrochemically exfoliated graphene nano-platelets were collected and redispersed in DMF to form inks. The printed film of conductivity ~2.5^103 S/m was obtained after annealing at 300 °C for one hour.

Water based GO/Ag hybrid inks were developed for screen printing. When high concentration GO aqueous dispersion was mixed with reactive silver ink, the viscosity of the mixture increased instantly to above 1000 cP as a result of reactions between oxygen functional groups (OFGs) on GO sheets and ingredients in the reactive silver ink. When the screen printed lines with different GO:Ag ratios were annealed in air, the conductivity of the resultant reduced graphene oxide/silver nanoparticles (RGO/AgNPX) composites decreased as silver content increased. As oxygen enriched compounds in RGO/AgNPX composites were detected, we proposed that AgOx compounds were generated on the AgNPs surface, which raised the contact resistance between AgNPs and RGO flakes. To solve this problem, the printed patterns were instead annealed in reducing gas (Ar/H2 5%). The electrical conductivity ~2.0^104 S/m was then achieved.

Furthermore, the reduction of GO using ammonium formate as reducing reagent was investigated. When applying a hydrothermal method, ammonium formate shows excellent reduction ability, surpassing the widely used reducing agent, L-ascorbic acid, under same condition. Elemental analysis shows the C/O ratio of RGO as high as ~11 and most OFGs were removed in the reduction process. Meanwhile, incorporated nitrogen atoms introduced active sites in resultant RGO, making it a promising electrocatalyst for oxygen reduction reaction.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. p. 64
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1780
Keywords
Exfoliation, Graphene inks, Inkjet printing, Screen printing, GO/Ag hybrid inks, Leuckart reaction, Reduction.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-377697 (URN)978-91-513-0588-2 (ISBN)
Public defence
2019-04-25, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Opponent
Supervisors
Available from: 2019-04-01 Created: 2019-02-25 Last updated: 2019-05-07

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Song, ManZhao, JieRiekehr, LarsGrennberg, HelenaZhang, Zhi-Bin

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