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Activated graphene as a material for supercapacitor electrodes: effects of surface area, pore size distribution and hydrophilicity
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.
Umeå University, Faculty of Science and Technology, Department of Physics.
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2019 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084Article in journal (Refereed) Epub ahead of print
Abstract [en]

Activated reduced graphene oxide (a-rGO) is a material with a rigid 3D porous structure and high specific surface area (SSA). Using variation of activation parameters and post-synthesis mechanical treatment we prepared two sets of materials with a broad range of BET (N2) SSA ∼1000–3000 m2 g−1, and significant differences in pore size distribution and oxygen content. The performance of activated graphene as an electrode in a supercapacitor with KOH electrolyte was correlated with the structural parameters of the materials and water sorption properties. a-rGO is a hydrophobic material as evidenced by the negligibly small BET (H2O) SSA determined using analysis of water vapor sorption isotherms. However, the total pore volume determined using water vapor sorption and sorption of liquid water is almost the same as the one found by analysis of nitrogen sorption isotherms. Ball milling is found to provide an improved bulk density of activated graphene and collapse of all pores except the smallest ones (<2 nm). A decrease in the activation temperature from 850 °C to 550 °C is found to result in materials with a narrow micropore size distribution and increased oxygen content. Elimination of mesopores using ball milling or a lower activation temperature provided materials with better specific capacitance despite a significant decrease (by ∼30%) of the BET (N2) SSA. The best gravimetric and volumetric capacitances in KOH electrolyte were achieved not for samples with the highest value of the BET (N2) SSA but for materials with 80–90% of the total pore volume in micropores and an increased BET (H2O) SSA. Comparing the performance of electrodes prepared using rGO and a-rGO shows that a more hydrophilic surface is favorable for charge storage in supercapacitors with KOH electrolyte.

Place, publisher, year, edition, pages
RSC Publishing, 2019.
Keywords [en]
graphene, energy storage, supercapacitors
National Category
Condensed Matter Physics
Research subject
Physical Chemistry
Identifiers
URN: urn:nbn:se:umu:diva-162087OAI: oai:DiVA.org:umu-162087DiVA, id: diva2:1342445
Available from: 2019-08-13 Created: 2019-08-13 Last updated: 2019-08-13

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Iakunkov, ArtemSkrypnychuk, VasylNordenström, AndreasTalyzin, Aleksandr V.

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