Thesis
Electrochemical supercapacitors from upcycled biomass and plastic waste derived activated carbon composites
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2024
- Thesis identifier
- T16856
- Person Identifier (Local)
- 201990197
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Flexible/Stretchable supercapacitors have emerged as attractive prospects forwearable and portable electronics among the next generation of energy storagedevices. These devices are resistant to shock, can be adapted to any curved surface,and provide a less energy-consuming alternative to flexible Lithium (Li)-ion batteries.So far, the most efficient electrodes materials for flexible/stretchable supercapacitorshave been based on carbon materials produced from fossil fuels, such as graphene,carbon nanotubes, and conductive polymers which are expensive and limited. As aresult, there is a need for the development of cost-effective and sustainable electrodematerials for the fabrication of flexible/stretchable supercapacitors.Biomass/plastic wastes pose a serious threat to the environment, and the massiveeconomy involved in the global disposal of biomass/plastic wastes has motivated usto recycle or reuse various categories of waste in order to gain value-added carbonproducts. Because of its large specific surface area, well-defined pore structure,excellent thermal and chemical durability, intrinsic high electrical conductivity, andwide availability, porous activated carbon (AC) is a common electroactive material forsupercapacitor applications. Over the last decade, a great deal of research has beendone on the biomass/plastic waste derived activated carbon; however, this researchhas largely concentrated on the electrodes alone or coin-cell type supercapacitors,that are unlikely to make the transfer from the laboratory to the real-world wearableand portable electronic applications. Underpinned by a design philosophy ofsustainability and scalability, the current research aims to use a diverse range ofbiomass/plastic wastes to create high surface area porous carbon materials that canbe used as electrodes in the fabrication of high energy density flexible/stretchablesupercapacitors with environmentally safe electrolytes such as bio-polymer gel andwater-in-salt electrolytes. Activated carbon derived from plant-based biomass(hazelnut shells, corn derivatives and pomelo peel) and plastic waste (Face shield andface mask) along with carbon composites with nanomaterials (siloxane, zinc cobaltoxide and tin sulphide) have been explored in this thesis for application as electrode material in electrochemical supercapacitors. Physicochemical properties of thesynthesized materials were determined by X-Ray diffraction (XRD), X-rayphotoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmissionelectron microscope (TEM), Raman Spectroscopy and N2 adsorption/desorptionanalyzer. The electrochemical performance of the as-prepared carbons wasinvestigated in both in three electrode system in aqueous electrolyte as well as in twoelectrode system via solid state supercapacitor using biopolymer gel electrolyte.This PhD thesis is structured into ten chapters. A short summary of those chapters isdescribed below.Chapter 1-3 includes a general introduction to fundamental principles ofsupercapacitors technology, biomass activated carbon and its composite electrodes,and electrolytes for supercapacitors. Additionally, the main motivation and objectivesof this PhD Thesis are briefly presented at the end of Chapter 3.Chapter 4 presents the synthesis of high specific surface area porous carbon fromhazelnut shells and their application in supercapacitors. By using a simple “sonoexfoliation method”, graphene like porous carbons was obtained from presynthesized activated carbon. It was observed that the textural and electrochemicalproperties of the as-prepared carbon materials enhanced significantly after sonoexfoliation process. The high surface area graphene-like carbon obtained after sonoexfoliation showed excellent electrochemical performance with specific capacitanceof 320.9 F g?1 at 0.2 A g?1current density and exceptional capacitance retention of77.8% at 2 A g?1current density after 10 000 cycles in 1 M Na2SO4 electrolyte.Furthermore, the symmetric flexible supercapacitor fabricated using sono-exfoliatedgraphene-like activated carbon and biopolymer gel electrolyte exhibits an outstandingenergy density of 38.7 W h kg?1 and power density of 198.4 W kg?1.Chapter 5 investigates the best possible precursor among different corn derivatives.The activated carbon (AC) obtained from corn grain possessed hierarchical porousstructure with appropriate amount of N, O functional groups, high specific surface area (1804 m2 g?1), and a high degree of graphitization and displayed the highestelectrochemical performance among the corn derived activated carbons with aspecific capacitance (411 F g?1 at 1.0 A g?1) and excellent rate capability (85.7%capacitance retention at 30 A g?1) in 6 M KOH aqueous electrolyte tested in threeelectrode configuration. High specific surface area and higher degree of graphitizationare observed to play a crucial role in determining the charge accumulation propertiesof activated carbon (AC) grain sample. Chapter 5 also investigated the electrochemicalbehavior of flexible symmetric supercapacitor based on slot-die coated AC grainelectrodes and hydroxyethyl cellulose (HEC)/KOH bio-polymer electrolyte whichdelivered an outstanding energy density of 31.1 W h kg?1 at 215 W kg?1 and ultra-highcyclic stability (91.3% after 10000 cycles at 5 A g?1current density).Chapter 6 presents the synthesis of novel biomass activated carbon compositeelectrodes and their applications in supercapacitors. Corn husk derived activatedcarbon/two-dimensional (2D) siloxene has been utilized as a novel compositeelectrode for fabricating high energy density and high temperature tolerantsupercapacitor. High surface area corn husk activated carbon was used in this study asa suitable framework for depositing siloxene nanosheets, allowing the overallsiloxene/corn husk derived activated carbon composite to give good electrochemicalperformance. The as-prepared composite electrode has a high specific capacitance of415 F g?1 at 0.25 A g?1 and retains 73.4% of its initial capacitance even at a high currentdensity of 30 A g?1in 1 M Na2SO4 electrolyte, thanks to the hierarchical porousstructure of activated carbon and sheet like siloxene structures. The siloxenenanosheet structures act as a spacer, exposing the surface-active sites of activatedcarbon for quick electrochemical reactions and ensuring maximum electrode materialutilisation. Furthermore, the symmetric supercapacitor assembled with the compositeelectrodes and “acetonitrile/water-in-salt (AWIS)” electrolyte displayed bestperformance with an outstanding energy density of 57.2 W h kg?1 at 338 W kg?1 witha cyclic stability of 92.8% after 10000 cycles at 5 A g?1current density. Besides, thefabricated supercapacitor can operate over wide temperature range from 0 to 100 ?C.
- Advisor / supervisor
- Berlouis, Leonard
- Ivaturi, Aruna
- Resource Type
- Note
- Previously held under moratorium from 13th March 2024 until 13th March 2025.
- DOI
- Funder
- Embargo Note
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