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Electrochemical Properties of Biobased Carbon Aerogels Decorated with Graphene Dots Synthesized from Biochar
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.ORCID iD: 0000-0002-3171-5979
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.ORCID iD: 0000-0002-1641-0448
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.ORCID iD: 0000-0003-2099-7605
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.ORCID iD: 0000-0003-1785-7177
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2021 (English)In: ACS Applied Electronic Materials, E-ISSN 2637-6113, Vol. 3, no 11, p. 4699-4710Article in journal (Refereed) Published
Abstract [en]

Carbon aerogels prepared from low-cost renewable resources are promising electrode materials for future energy storage applications. However, their electrochemical properties must be significantly improved to match the commercially used high-carbon petroleum products. This paper presents a facile method for the green synthesis of carbon aerogels (CAs) from lignocellulosic materials and graphene dots (GDs) from commercially available biochar. The produced carbon aerogels exhibited a hierarchical porous structure, which facilitates energy storage by forming an electrical double-layer capacitance. Surprisingly, the electrochemical analyses of the GD-doped carbon aerogels revealed that in comparison to pristine carbon aerogels, the surface doping of GDs enhanced the electrochemical performance of carbon aerogels, which can be attributed to the combined effect from both double-layer capacitance and pseudocapacitance. Herein, we designed and demonstrated the efficacy of a supercapacitor device using our green carbon electrode as a sustainable option. These green carbon aerogels have opened a window for their practical use in designing sustainable energy storage devices. 

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2021. Vol. 3, no 11, p. 4699-4710
Keywords [en]
graphene dots, cellulose nanofibers, kraft lignin, carbon aerogels, electrochemical properties
National Category
Materials Chemistry
Research subject
Wood and Bionanocomposites; Experimental Physics
Identifiers
URN: urn:nbn:se:ltu:diva-87706DOI: 10.1021/acsaelm.1c00487ISI: 000756989100004Scopus ID: 2-s2.0-85118673944OAI: oai:DiVA.org:ltu-87706DiVA, id: diva2:1607426
Note

Validerad;2021;Nivå 2;2021-11-30 (johcin)

Available from: 2021-11-01 Created: 2021-11-01 Last updated: 2023-09-05Bibliographically approved
In thesis
1. Trees to supercapacitors: green energy storage for sustainable future
Open this publication in new window or tab >>Trees to supercapacitors: green energy storage for sustainable future
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Currently the world is transitioning to a fossil free and circular economy-based development to achieve the environmental and climate objectives along with the sustainable development goals. To achieve this target, efficient use of resource materials is important, which can increase the lifetime and economic value of the resources while decreasing both the extraction of new raw materials and landfill waste. Hence replacing conventional fossil based raw materials with bio-based raw materials play an important role in the circular economy. In addition to that, lack of green and environment friendly energy storage systems to meet the increasing global energy demand is another major challenge faced by countries across the world. Within this context, the overall objective of this study is to use biomass based raw materials for the development of biocarbon that can make energy storage “greener”, thereby addressing the sustainability objectives and energy storage demands. 

In this work, the second most abundant biopolymer on earth, lignin has been utilized as the raw material for making carbon aerogels (CAs) which are extremely light, hierarchically porous, having high specific surface area with interconnected microstructure and mechanically stable. CAs were prepared by carbonizing the aerogels prepared using lignin and cellulose nanofibers (CNFs). Lignin and CNFs were mixed to make aqueous lignin/CNF suspensions which were subjected to unidirectional ice-templating process to obtain directionally arranged ice crystals in the frozen suspension. Freeze drying was performed for sublimating the ice crystals resulting in lignin/CNFs aerogels with directional porosity. These lignin/CNFs aerogels were further carbonized to obtain CAs which were evaluated for their suitability as supercapacitor electrodes. 

Results from this work demonstrated the potential of lignin-based carbon aerogels as suitable materials for future energy storage applications. Kraft lignin (KL) based CAs showed superior properties compared to soda lignin (SL) based CAs. The type of CNF used, whose function is to modify the rheology of lignin/CNF suspensions and act as sacrificial template during carbonization, was also shown to have an impact on the microstructure of CAs. Mechanically fibrillated CNFs resulted in CAs with more mesoporous (pore size between 2-50 nm) microstructure which is advantageous of energy storage applications. Graphene quantum dots (GQDs) prepared from biochar was used as capacitance enhancer for KL based CAs. Introduction of GQDs on the surface of CAs resulted in the improvement of specific capacitance. Further improvement in the microstructure and specific capacitance was achieved by controlling the process parameters during ice-templating process. Ice templating cooling rate and solid content of lignin/CNFs suspensions were varied systematically and observed that ice templating cooling rate had predominant influence on the microstructure of CAs. Effect of carbonization temperature on the final carbon structure was investigated by preparing carbon particles from different technical lignins and the results showed that carbon particles produced from SL is more graphitic and electrically conductive. The dependance of microstructure on the ice templating cooling rate was utilized for the preparation of CAs reinforced carbon epoxy composites with superior mechanical properties. 

In summary, this thesis demonstrates that unidirectional ice-templating, freeze drying followed by direct carbonization route of preparation of lignin based CAs is a green and effective strategy for making supercapacitor electrodes for energy storage application. Results indicated that type of lignin, ice-templating cooling rate, and carbonization temperature affect the microstructure and electrochemical performance of the carbon electrodes. This study opens new opportunities to investigate the usage of lignin-based carbon materials for meeting the demands of future energy storage devices. 

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2022
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Other Materials Engineering
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-93688 (URN)978-91-8048-200-4 (ISBN)978-91-8048-201-1 (ISBN)
Public defence
2022-12-16, E246, Luleå tekniska universitet, Luleå, 10:00 (English)
Opponent
Supervisors
Available from: 2022-10-24 Created: 2022-10-22 Last updated: 2023-10-06Bibliographically approved

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Thomas, BonyGeorge, GejoLandström, AntonConcina, IsabellaGeng, ShiyuVomiero, AlbertoSain, MohiniOksman, Kristiina

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