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Advanced Carbon Materials for Environmental and Energy ApplicationsDua, Rubal 05 1900 (has links)
Carbon based materials, including porous carbons and carbon layer composites, are finding increased usage in latest environmental and energy related research. Among porous carbon materials, hierarchical porous carbons with multi-modal porosity are proving out to be an effective solution for applications where the traditional activated carbons fail. Thus, there has been a lot of recent interest in developing low-cost, facile, easy to scale-up, synthesis techniques for producing such multi-modal porous carbons. This dissertation offers two novel synthesis techniques: (i) ice templating integrated with hard templating, and (ii) salt templating coupled with hard templating, for producing such hierarchically porous carbons. The techniques offer tight control and tunability of porosity (macro- meso- and microscale) in terms of both size and extent. The synthesized multi-modal porous carbons are shown to be an effective solution for three important environment related applications – (i) Carbon dioxide capture using amine supported hierarchical porous carbons, (ii) Reduction in irreversible fouling of membranes used for wastewater reuse through a deposition of a layer of hierarchical porous carbons on the membrane surface, (iii) Electrode materials for electrosorptive applications. Finally, because of their tunability, the synthesized multi-modal porous carbons serve as excellent model systems for understanding the effect of different types of porosity on the performance of porous carbons for these applications. Also, recently, there has been a lot of interest in developing protective layer coatings for preventing photo-corrosion of semiconductor structures (in particular Cu2O) used for photoelectrochemical water splitting. Most of the developed protective strategies to date involve the use of metals or co-catalyst in the protective layer. Thus there is a big need for developing low-cost, facile and easy to scale protective coating strategies. Based on the expertise gained in synthesizing porous carbon materials, and owing to our group’s interest in developing suitable photoelectrode materials, this dissertation also proposes a novel carbon-Cu2O composite comprising of a carbon layer coated Cu2O nanowire array structure as a high performance and stable photoelectrode material for photoelectrochemical water splitting.
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Enhanced Energy Storage and Conversion Applications by Porous Carbon and Atomic Layer DepositionAbdelmoaty, Yomna H 01 January 2017 (has links)
The design and synthesis of porous materials attracted great attention recently because of their potential use in many fields like clean energy and environmental protection. Herein, we introduced new synthetic approaches for the preparation for porous carbons and organic polymers for selective CO2 and iodine capture application. Regarding CO2 capture application, Two new
series of porous carbons (PYDCs) and (TRI-Ps) were synthesized by thermally activating Pyrazole and Triazolo Pyridine monomers respectively using KOH as a catalyst, which leads to porous carbon. PYDCs exhibit high surface area according to Brunauer–Emmett–Tellertheory (SABET = 1266–2013 m2 g−1), high CO2 Isosetric heat Qst(33.2-37.1 kJ/mol) and significantly high CO2 uptakes 8.59mmol g−1 (1bar) at 273k. The reported porous carbons also show significantly high adsorption selectivity for CO2/N2 (128) and CO2/CH4 (13.4) according to Ideal adsorbed solution theory (IAST) calculation using pure gas isotherms at 298 K. TRI-Ps exhibit high surface area (SABET=1852- 2917 m2 g−1) with a combination of mesoporous and microporous pores. TRI-Ps exhibit CO2 capture capacity of 6.98mmol g−1 at 1 bar and 273K. The development of majority of microporous offered a high CO2 storage capacity to TRI-Ps. High CO2 uptake achieved as a result of preferable pore size, surface area, and high oxygen content and high Qst values. Based on IAST calculation, high CO2/N2 selectivity (113.9) at 298K was achieved.
Regarding iodine capture application, two new series of porous organic polymers Benzamidizole Linked Polymers (BILPs) and nitrogen rich porous Polymers (NRPPs) were synthesized and tested. Iodine capture, sorption isotherm and kinetics of adsorption were studied. BILPs exhibit iodine uptake capacity of 227.8 wt.% and 202.8 wt. % for BILP-A and BILP-B respectively. BILP-A shows ability of releasing 95.8% of captured iodine, while, BILP-B released 82.22%. Sorption curves were fitted by Freundlich equation indicating a heterogeneity of adsorption process on the surface. NRPPs exhibit iodine capacity of 192.35 wt.% and 222.35 wt. % for NRPP-1 and NRPP-2 respectively. NRPPs shows ability of releasing the majority of adsorbed Iodine. Sorption curves were fitted by Langmuir equation indicating a heterogeneity of adsorption process on the surface.
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Synthesis and Structural Analyses of Activated Porous Carbon Derived from Silica TemplateSu, Yuan-Hao 26 July 2011 (has links)
This research mainly includes two parts. First, monodispersed silica spheres with diameter about 58 and 73 nm were successfully synthesized. The tablet-like silica template could be made using a stainless steel mold by pressing the mold with a pressure ~ 10 MPa. The advantage of this molding process is it takes only a short time to accomplish the total fabrication. Second, infiltration of the carbon precursor was done using the monomers resorcinol (R) and furfural (F) in the interval of tablet-like silica template, and then polymerization and drying. It was subsequently carbonized in N2 atmosphere at 800 ¢J and then the silica template was removed by 20 wt % HF solution. The activated porous carbon material has larger specific surface area than the traditional powder carbon material. The chemical activation process by KOH plays a vital role in raising the specific surface area, since the KOH would etch the carbon pore surface to produce a large number of micropores (diameter < 2 nm), forming a macro-micro or meso-micro porous carbon materials.
The F/R molar ratios for polymerization between 2.0 to 3.0 were applied and the carbon yields of these resins were higher than 51% in this range. An F/R ratio below 2.0 or 3.0 gave a lower carbon yield when carbonization at 800 ¢J. X-ray diffraction analyses on the macroporous carbon materials indicate a semi-crystalline structure which belong to the hexagonal crystal system with (002) d-spacing of = 0.373 nm, which is larger than the 0.339 nm of graphite. In Raman spectra analysis, the integral area of D-peak (ID) and G-peak (IG) is an index to define the degree of graphitization. The ratios ID/IG of lie between 1.7 - 1.8, which are larger than that of graphite (ID/IG = 0.1 - 0.3), so the FR series macroporous carbon is mostly amorphous and is far from highly crystallized structure. The un-activated macroporous carbon materials has open pore structure, the pore diameter is 56 nm which is classified to the macroporous scale.
The nitrogen adsorption/desorption isotherm of the porous carbon materials belongs to the type IV, with H1 type hysteresis. The BET results show that the specific surface area increases with increasing KOH concentration; whereas the open pore structure remain the same. SEM observations reveal the pore structure doesn¡¦t collapse but the pore wall does become thinner. From this work, macroporous carbon materials with total pore volume as high as 2.23 cm3/g and the specific surface area as high as 658 m2/g have successfully been synthesized. Activation by KOH creates more micropores on its carbon walls, resulting in a macro-microporous carbon material having two scales of pores in the same time and with a high surface area of 1404 m2/g.
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Préparation de matériaux d’électrode pour l’élimination et la valorisation de polluants azotés / Preparation of electrode materials for removal and valorization of nitrogenous pollutantsMirzaei, Peyman 16 October 2018 (has links)
Les technologies de traitement physico-chimique et biologique des eaux usées ne permettent pas un traitement efficace de l’azote puisque 40% est encore rejeté en rivière. La thèse porte sur le développement de nouveaux matériaux d’électrode pour la conversion des polluants azotés (nitrates, urée) en produits valorisables (NH3, H2) ou inertes (N2). Le travail consiste à synthétiser des matériaux composites constitués de nanoparticules mono ou bimétalliques jouant le rôle de catalyseurs, dispersées dans des carbones de grande surface spécifique. La forme ultra-divisée permet d’augmenter les surfaces actives et ainsi réduire les quantités de métal. Ces produits sont caractérisés par Microscopie Electronique à Balayage et en Transmission, par analyses ICP et DRX pour décrire leur morphologie, composition et structure. Des études électrochimiques analytiques sont ensuite réalisées à l’aide d’une MicroÉlectrode à Cavité afin de déterminer l’activité électro-catalytique des matériaux et accéder à des aspects mécanistiques. La première partie de la thèse a concerné l’électro-réduction des nitrates. Des composites Cu-Rh/C et Cu-Ni/C avec différentes compositions ont été synthétisés par une méthode chimique consistant à imprégner le carbone par des sels métalliques puis à les réduire par NaBH4 en présence d’un surfactant (CTAB). Les particules présentent des tailles d’environ 2 nm de diamètre. Ces bimétalliques présentent des courants plus élevés que ceux obtenus avec des particules monométalliques. En particulier, dans le cas du système Cu-Rh, il a été mis en évidence un comportement « bi-fonctionnel » où le cuivre réduit les nitrates en nitrites et le rhodium les nitrites en ammoniaque. Des matériaux composites ont ensuite été synthétisés dans les mêmes conditions mais en utilisant un carbone greffé afin de contrôler la dispersion et l’ancrage des nanoparticules. Pour cela, les carbones sont préalablement greffés par des groupements aryle avec substituant puis décorés des nanoparticules métalliques. Le but est de déterminer les conditions de greffage optimales conduisant aux réactivités les plus élevées en contrôlant l’épaisseur des films organiques greffés et la nature du substituant (-SH, -NH2, -COOH). La seconde partie de la thèse a concerné l’électro-oxydation de l’urée. Cette réaction est généralement effectuée sur des matériaux à base de nickel et, d’après la littérature, l’ajout d’un co-élément permet de modifier les propriétés électrochimiques (potentiel, intensité). Une étude sur des composites bimétalliques Ni100-xMx / C avec M = Co, Rh, Mn, Fe (selon la méthode déjà décrite ci-dessus) a été conduite pour déterminer le rôle de différents co-éléments. Le rhodium est apparu comme l’élément apportant la meilleure intensité et la meilleure stabilité. Une étude plus complète a alors été réalisée avec la synthèse de composites Ni100-xRhx / C avec différentes compositions par réduction des ions métalliques sous Ar/H2 dans un four à température modérée (500°C). L'oxydation électrochimique de l'urée est significativement améliorée par l'ajout de rhodium qui induit une forte diminution de la taille des nanoparticules (de 15 nm pour le nickel et à 2 nm le rhodium). Ce travail de thèse a montré l’intérêt d’utiliser des catalyseurs bimétalliques dispersés dans des matrices carbonées pour le traitement de polluants azotés. Elle confirme par ailleurs que la Microélectrode à Cavité est un outil performant pour l’étude des poudres grâce à la bonne résolution des signaux électrochimiques. La perspective la plus intéressante de ce travail est de poursuivre l’étude de l’électrocatalyse de l’urée sur les Ni-M/C pour pouvoir dépolluer l’urine tout en produisant à faible coût de l’hydrogène comme moyen de stockage de l’électricité renouvelable. Il a permis d’initier des collaborations avec d’autres laboratoires et un industriel de l’assainissement des eaux en vue de traiter de l’urine collectée à la source / Physico-chemical and biological wastewater treatment technologies do not allow efficient nitrogen treatment since 40% is still discharged into rivers. The thesis concerns the development of new electrode materials for the conversion of nitrogenous pollutants (nitrates, urea) into recoverable (NH3, H2) or inert products (N2). The work consists in synthesizing composite materials made of mono or bimetallic nanoparticles acting as catalysts, dispersed in large surface area carbons. The ultra-divided shape increases the active surface and thus reduces the amount of metal. These products are characterized by Scanning and Transmission Electron Microscopy, ICP and DRX analysis to describe their morphology, composition and structure. Electrochemical analytical studies are then carried out using a Cavity MicroElectrode to determine the electro-catalytic activity of the materials and access mechanistic aspects.The first part of the thesis concerned the electro-reduction of nitrates. Cu-Rh/C and Cu-Ni/C composites with different compositions were synthesized by a chemical method consisting of impregnating the carbon with metal salts and then reducing them with NaBH4 in the presence of a surfactant (CTAB). The particles are approximately 2 nm in diameter. These bimetals have higher currents than those obtained with monometallic particles. In particular, in the case of the Cu-Rh system, a "bi-functional" behavior has been demonstrated where copper reduces nitrates to nitrites and rhodium reduces nitrites to ammonia. Composite materials were then synthesized under the same conditions by using grafted carbon to control the dispersion and anchoring of nanoparticles. For this, the carbons are previously grafted by aryl groups with a substituent and then decorated with metal nanoparticles. The aim is to determine the optimal grafting conditions leading to the highest reactivity by controlling the thickness of the grafted organic films and the nature of the substituent (-SH, -NH2, -COOH). The second part of the thesis concerned the electro-oxidation of urea. This reaction is generally carried out on nickel-based materials and, according to the literature, the addition of a co-element makes it possible to modify the electrochemical properties (potential, intensity). A study on bimetallic composites Ni100-xMx / C with M = Co, Rh, Mn, Fe (according to the method described above) was conducted to determine the role of the different co-elements. Rhodium appeared as the element providing the best intensity and the best stability. A more complete study was then carried out by synthesizing Ni100-xRhx / C composites with different compositions through the reduction of metal ions under Ar/H2 in a furnace at moderate temperature (500°C). The electrochemical oxidation of urea is significantly improved by the addition of rhodium which induces a strong decrease in the nanoparticle size (from 15 nm for nickel to 2 nm for rhodium). This thesis work has shown the interest of using bimetallic catalysts dispersed in carbon matrices for the treatment of nitrogenous pollutants. It also confirms that the Cavity Microelectrode is a powerful tool for the study of powders thanks to the good resolution of electrochemical signals.The most interesting perspective of this work is to continue the study of urea electrocatalysis on Ni-M/C to be able to depollute urine while producing hydrogen at low cost for chemical storage of renewable electricity. It has enabled collaborations to be initiated with other laboratories and a water purification industrial company to treat urine collected separately
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Preparação e caracterização de materiais de carbono via termopolimerização de pré-polímero fenol-formaldeído / Preparation and characterization of carbon materials by thermopolimerization of pre-polymer phenol-formaldehydeMuscelli, Wesley Cardoso 17 August 2012 (has links)
O presente trabalho relata a investigação de uma rota reprodutível de obtenção de materiais de carbono a partir do tratamento térmico de pré-polímero fenol formaldeído (resina fenólica) levando em consideração características morfológicas e estruturais.O controle da composição de resina bem como o estabelecimento cuidadoso da rampa de aquecimento foram fatores decisisvos para a obtenção de materiais análogos ao carbono vítreo de maneira reprodutível. Os materiais obtidos apresentaram reduzida presença de poros e condutividade térmica apreciável uma vez que foram testados como eletrodos de trabalho em ensaios eletroquímicos . A análise estrutural e morfológica dos compostos sintetizados demonstrou a presença de estrutura semelhante ao carbono vítreo relatado na literatura com presença de poucos poros superficiais da ordem de micrômetros até nanômetros. Já em relação aos materias de carbono porosos, buscou-se obter compostos com arranjo ordenado de mesoporos. Resultados preliminares demonstraram que os materiais apresentaram poros micrométricos superficiais organizados. / The present work reports on the investigation of reproducible route to synthesize carbon materials from phenolic resin take into account the structural and morphological features. The control or the resin composotion and the careful establinshing of the ramp heating were decisive for achievement the materials analogous to the glassy carbon (vitreous carbon) in a reproducicle way. The materials obtained materials revealed the glassy carbon structure with the presence of the superficial pores in the range of micrometers to nanometrers. In relation to the carbon materilas, they organized arrangement of the porous in the micrometric scale.
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Chalcogen-carbon nanocomposite cathodes for rechargeable lithium batteriesLee, Jung Tae 12 January 2015 (has links)
Current electrochemical energy storage systems are not sufficient to meet ever-rising energy storage requirements of emerging technologies. Hence, development of alternative electrode materials is inevitable. This thesis aims to establish novel electrode materials demonstrating both high energy and power density with prolonged cycle life derived from fundamental understandings on electrochemical reactions of chalcogens, such as sulfur (S) and selenium (Se). First, the effects of the pore size distribution, pore volume and specific surface area of porous carbons on the temperature-dependent electrochemical performance of S-infiltrated carbon cathodes in electrolytes having different salt concentrations are investigated. Additionally, the carbide derived carbon (CDC) synthesis temperature, electrolyte composition, and electrochemical S utilization have been correlated. The effects of thin Li-ion permeable but polysulfide non-permeable Al2O3 layer coating on the surface of S infiltrated carbon cathode are also examined. Similar with S studies, Se infiltrated ordered meso- and microporous CDC composites are prepared and the correlations between pore structure designing and electrolyte molarity are explored. Finally, this thesis demonstrates a simple process to form a protective solid electrolyte layer on the Se cathode surface in-situ. This technique adopts fluoroethylene carbonate to convert into a layer that remains permeable to Li ions, but prevents transport of polyselenides. As a whole, the correlations of multiple cell parameters, such as the cathode structure, the electrolyte composition, and operating temperature on the performances of lithium-chalcogen batteries are discussed.
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Nanoporous Conducting MaterialsJanuary 2012 (has links)
abstract: Nanoporous electrically conducting materials can be prepared with high specific pore volumes and surface areas which make them well-suited for a wide variety of technologies including separation, catalysis and owing to their conductivity, energy related applications like solar cells, batteries and capacitors. General synthetic methods for nanoporous conducting materials that exhibit fine property control as well as facility and efficiency in their implementation continue to be highly sought after. Here, general methods for the synthesis of nanoporous conducting materials and their characterization are presented. Antimony-doped tin oxide (ATO), a transparent conducting oxide (TCO), and nanoporous conducting carbon can be prepared through the step-wise synthesis of interpenetrating inorganic/organic networks using well-established sol-gel methodology. The one-pot method produces an inorganic gel first that encompasses a solution of organic precursors. The surface of the inorganic gel subsequently catalyzes the formation of an organic gel network that interpenetrates throughout the inorganic gel network. These mutually supporting gel networks strengthen one another and allow for the use of evaporative drying methods and heat treatments that would usually destroy the porosity of an unsupported gel network. The composite gel is then selectively treated to either remove the organic network to provide a porous inorganic network, as is the case for antimony-doped tin oxide, or the inorganic network can be removed to generate a porous carbon material. The method exhibits flexibility in that the pore structure of the final porous material can be modified through the variation of the synthetic conditions. Additionally, porous carbons of hierarchical pore size distributions can be prepared by using wet alumina gel as a template dispersion medium and as a template itself. Alumina gels exhibit thixotropy, which is the ability of a solid to be sheared to a liquid state and upon removal of the shear force, return to a solid gel state. Alumina gels were prepared and blended with monomer solutions and sacrificial template particles to produce wet gel composites. These composites could then be treated to remove the alumina and template particles to generate hierarchically porous carbon. / Dissertation/Thesis / Ph.D. Chemistry 2012
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Carbon Nanomaterials for Energy Storage, Actuators and Environmental ApplicationsJanuary 2015 (has links)
abstract: Carbon nanomaterials have caught tremendous attention in the last few decades due to their unique physical and chemical properties. Tremendous effort has been made to develop new synthesis techniques for carbon nanomaterials and investigate their properties for different applications. In this work, carbon nanospheres (CNSs), carbon foams (CF), and single-walled carbon nanotubes (SWNTs) were studied for various applications, including water treatment, energy storage, actuators, and sensors.
A facile spray pyrolysis synthesis technique was developed to synthesize individual CNSs with specific surface area (SSA) up to 1106 m2/g. The hollow CNSs showed adsorption of up to 300 mg rhodamine B dye per gram carbon, which is more than 15 times higher than that observed for conventional carbon black. They were also evaluated as adsorbents for removal of arsenate and selenate from water and displayed good binding to both species, outperforming commercial activated carbons for arsenate removal in pH > 8. When evaluated as supercapacitor electrode materials, specific capacitances of up to 112 F/g at a current density of 0.1 A/g were observed. When used as Li-ion battery anode materials, the CNSs achieved a discharge capacity of 270 mAh/g at a current density of 372 mA/g (1C), which is 4-fold higher than that of commercial graphite anode.
Carbon foams were synthesized using direct pyrolysis and had SSA up to 2340 m2/g. When used as supercapacitor electrode materials, a specific capacitance up to 280 F/g was achieved at current density of 0.1 A/g and remained as high as 207 F/g, even at a high current density of 10 A/g.
A printed walking robot was made from common plastic films and coatings of SWNTs. The solid-state thermal bimorph actuators were multifunctional energy transducers powered by heat, light, or electricity. The actuators were also investigated for photo/thermal detection. Electrochemical actuators based on MnO2 were also studied for potential underwater applications.
SWNTs were also used to fabricate printable electrodes for trace Cr(VI) detection, which displayed sensitivity up to 500 nA/ppb for Cr(VI). The limit of detection was shown to be as low as 5 ppb. A flow detection system based on CNT/printed electrodes was also demonstrated. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2015
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Preparação e caracterização de materiais de carbono via termopolimerização de pré-polímero fenol-formaldeído / Preparation and characterization of carbon materials by thermopolimerization of pre-polymer phenol-formaldehydeWesley Cardoso Muscelli 17 August 2012 (has links)
O presente trabalho relata a investigação de uma rota reprodutível de obtenção de materiais de carbono a partir do tratamento térmico de pré-polímero fenol formaldeído (resina fenólica) levando em consideração características morfológicas e estruturais.O controle da composição de resina bem como o estabelecimento cuidadoso da rampa de aquecimento foram fatores decisisvos para a obtenção de materiais análogos ao carbono vítreo de maneira reprodutível. Os materiais obtidos apresentaram reduzida presença de poros e condutividade térmica apreciável uma vez que foram testados como eletrodos de trabalho em ensaios eletroquímicos . A análise estrutural e morfológica dos compostos sintetizados demonstrou a presença de estrutura semelhante ao carbono vítreo relatado na literatura com presença de poucos poros superficiais da ordem de micrômetros até nanômetros. Já em relação aos materias de carbono porosos, buscou-se obter compostos com arranjo ordenado de mesoporos. Resultados preliminares demonstraram que os materiais apresentaram poros micrométricos superficiais organizados. / The present work reports on the investigation of reproducible route to synthesize carbon materials from phenolic resin take into account the structural and morphological features. The control or the resin composotion and the careful establinshing of the ramp heating were decisive for achievement the materials analogous to the glassy carbon (vitreous carbon) in a reproducicle way. The materials obtained materials revealed the glassy carbon structure with the presence of the superficial pores in the range of micrometers to nanometrers. In relation to the carbon materilas, they organized arrangement of the porous in the micrometric scale.
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RENEWABLE CARBON FROM LIGNIN BIOMASS AND ITS ELECTRODE AND CATALYST APPLICATIONS IN BATTERIES, SUPERCAPACITORS, AND FUEL CELLSdemir, muslum 01 January 2017 (has links)
Over the last century, almost all of the carbon materials developed for the energy industry are derived from fossil fuels. The growing global concerns about energy needs, fossil fuels consumption, and the related environmental issues have motived scientists to find new, green and sustainable energy resources such as the wind, solar and biomass energy. Essentially, biomass-derived materials can be utilized in energy storage and conversion devices such as Li-ion batteries, fuel cells, and supercapacitors. Among the biomass resources, lignin is a high volume byproduct from the pulp and paper industry and is currently burned to generate electricity and steam. The pulp and paper industry has been searching for high value-added uses of lignin to improve its overall process economics.
The importance of manufacturing valuable materials from lignin is, discussed in Chapter 2, demonstrating the need for a facile, green and scalable approach to synthesize bio-char and porous carbon for use in Li-ion batteries. From this context, lignin is first carbonized in water at 300 °C and 103 bar to produce bio-char, which is then graphitized using a metal nitrate catalyst at 900-1100 °C in an inert gas at 1 bar. Graphitization effectiveness of three different catalysts, iron, cobalt and manganese nitrates was examined. The obtained materials were analyzed for morphology, thermal stability, surface properties, and electrical conductivity. Both annealing temperature and the catalyst affects the degree of graphitization. High-quality graphitization is obtained by using Mn(NO3)2 at 900 °C or Co(NO3)2 catalysts at 1100 °C.
Research on various energy storage materials for supercapacitors has grown rapidly in the recent years. Various advanced materials have been shown as a promising candidate for future’s high-energy supercapacitor electrodes. For a material in a supercapacitor electrode to be considered, it must show promising results for its specific power and energy density, electrical conductivity, surface properties, durability, surface area and pore-size distribution in order to design and develop high-performance supercapacitor devices. The industrial applications of supercapacitors have not been satisfied due to the low energy density (the commercially available supercapacitors have between 5 to 10 times less energy density than that of batteries) and moderate charge-discharge rate of supercapacitor electrode. Thus, chapter 3 was aimed to design and synthesize nitrogen-doped carbon materials that show the characteristic of high-energy and high-power density supercapacitor electrodes with a long cycle life. With this aim, organosol lignin was successfully converted into N-doped carbon materials using a two-step conversion process. The nitrogen content in the carbon was up to 5.6 wt.%. The synthesize materials exhibit high surface area up to 2957 m2/g with micro/meso porosity and a sheet-like structure. The N-doped carbon produced at 850 oC exhibited a high capacitance value of 440 F g-1 at a 1 mV s-1 scan rate and demonstrated excellent cyclic stability over 30,000 cycles in 1 M KOH. In addition, the NC-850 delivers a high energy density of 15.3 W h kg-1 and power density of 55.1 W kg−1 at 1 mV s-1. Therefore, this study suggests that N-doped carbon materials synthesized from a pulp and paper byproduct, lignin, are promising environmentally-sustainable candidates for supercapacitor applications.
Challenges for commercialization of fuel cells include high operation cost, inadequate operational stability, and poisoning by H2O2. To address the challenge, costly Pt-based catalysts are needed in order to facilitate the oxygen reduction reaction (ORR) at the cathode and the hydrogen oxidation reaction (HOR) at the anode. In chapter 4, alternative metal-free ORR catalyst materials derived from lignin are studied in order to simultaneously enhance the catalytic activity, lessen the Pt dependency and reduce the excessive costs associated. Calcium sulfonate lignin was successfully converted into sulfur self-doped carbons via in-situ hydrothermal carbonization and followed by post-annealing treatment. The sulfur content in the as-prepared porous carbons is up to 3.2 wt.%. The resulting materials displayed high surface areas (up to 660 m2 g-1) with micro/meso porosity and graphitic/amorphous carbon structure. The as-prepared sulfur self-doped electrode materials (SC-850) were tested as a potential cathodic material for ORR. The number of electrons transferred per molecule was measured to be ~ 3.4 at 0.8 V, which approaches the optimum 4 electron pathway. Additionally, S-doped materials were also applied as a supercapacitor electrode material. The SC-850 electrode exhibited a high specific and volumetric capacitance values of 225 F g-1 and 300 F cm-3 at a scan rate of 0.5 A g-1. The SC-850 electrode also exhibited consistent response over 10,000 cycles at harsh conditions. It was shown that the metal-free SC-850 is a promising electrode material for supercapacitors and ORR applications.
All of the studies presented in this dissertation involve the development and application of carbon-based materials derived from lignin and its application towards the Li-ion batteries, supercapacitor, and fuel cell. Insight into the applicability of lignin-derived carbon materials towards electrochemical applications is made readily available, supplemented by detailed physical, chemical and electrochemical characterization, to examine the specific factors influencing the Li-ion batteries, supercapacitor, and electrocatalysis of fuel cell activity.
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