Dissertations / Theses on the topic 'Na/MnO2 Cells'

The modification of anode materials is important to enhance the power generation of MFCs (microbial fuel cells). A novel and cost-effective modified anode that is fabricated by dispersing manganese dioxide (MnO2) and HNTs (Halloysite nanotubes) on carbon cloth to improve the MFCs' power production was reported. The results show that the MnO2/HNT anodes acquire more bacteria and provide greater kinetic activity and power density compared to the unmodified anode. Among all modified anodes, 75 wt% MnO2/HNT exhibits the highest electrochemical performance. The maximum power density is 767.3 mWm(-2), which 21.6 higher than the unmodified anode (631 mW/m(2)). Besides, CE (Coulombic efficiency) was improved 20.7, indicating that more chemical energy transformed to electricity. XRD (X-Ray powder diffraction) and FTIR (Fourier transform infrared spectroscopy) are used to characterize the structure and functional groups of the anode. CV (cyclic voltammetry) scans and SEM (scanning electron microscope) images demonstrate that the measured power density is associated with the attachment of bacteria, the microorganism morphology differed between the modified and the original anode. These findings demonstrate that MnO2/FINT nanocomposites can alter the characteristics of carbon cloth anodes to effectively modify the anode for practical MFC applications. (C) 2016 Elsevier Ltd. All rights reserved.

Une pile à combustible microbiennes (PCM) est un dispositif capable de produire de l’énergie électrique à partir d’énergie chimique grâce à l’activité catalytique des bactéries en présence de combustibles organiques. Ces travaux de thèse ont eu pour objectif la synthèse des nouveaux matériaux d’anode et de cathode qui pourraient constituer des alternatives aux matériaux à base de platine. Coté anode, nous avons synthétisé des matériaux par précipitation chimique sur du graphite en poudre à partir de mélanges contenant des ions ferreux et sulfures. Les caractérisations physicochimiques ont montré la formation de composés soufrés (mackinawite, polysulfures et soufre élémentaire) qui se transforment en produits soufrés plus oxydés en présence d’air. La formation de vivianite a été confirmée dans le cas d’un excès d’ions ferreux par rapport aux ions sulfures. Les analyses électrochimiques montrent que ces matériaux ont un comportement réversible avec des densités de courant d’oxydation élevées à bas potentiel. Coté cathode, nous avons choisi la synthèse par voie électrochimique d’un film de MnOx sur substrat d’acier inoxydable. Les caractérisations physicochimiques ont démontré la formation de la birnessite. Les analyses électrochimiques montrent que la réduction de ce matériau conduit à des courants cathodiques significatifs mais avec une réversibilité limitée, même en présence d’air. La réalisation de prototypes de PCM dans lesquels l’anode à base de composés soufrés est immergée dans une solution de terreau et la cathode à base de MnOx est au contact de l’air, a permis d’obtenir des puissances instantanées maximales de l’ordre de 12 W.m-3 et 1,8 W.m-2, et des densités de courant de l’ordre de 25 A.m-3 et 3,8 A.m-2. Un travail d’optimisation du fonctionnement de PCM a été réalisé. Ainsi, l’augmentation de la conductivité de la solution anodique et la diminution de quantité de sédiment dans la solution de terreau a permis d’améliorer la réponse électrochimique du matériau anodique et d’obtenir des puissances instantanées maximales de l’ordre de 17,5 W.m-3 et 2,7 W.m-2, et des densités de courant de l’ordre de 60 A.m-3 et 9,2 A.m-2. Le facteur limitant reste toujours le comportement électrochimique du film de MnOx
A microbial fuel cell (MFC) is a device allowing the production of electric power from chemical energy thanks to the catalytic activity of bacteria in presence of organic fuel. These works aimed the synthesis of new anode and cathode materials which could be an alternative to platinum materials. On the anode side, we synthesized the materials by chemical precipitation on powder graphite from mixtures containing ferrous and sulfide ions. Physicochemical characterizations showed the formation of sulfur compounds (mackinawite, polysulfide and elementary sulfur) which transform into sulfur products more oxidized in presence of air. Formation of vivianite was confirmed in the case of an excess of ferrous ions in relation to sulfide ions. Electrochemical analysis shows that these materials have a reversible behavior with high current densities at low voltage. On the cathode side, we chose electrochemical synthesis of an MnOx film on stainless steel substrate. Physicochemical characterizations showed birnessite formation. Electrochemical analysis show that the reduction of this material Leeds to significative cathodic currents but with a limited reversibility, even in presence of air. The realization of MFC prototypes in which the sulfur compounds-based anode is submerged in compost solution and the MnOx-based cathode is in contact with air, allowed the getting of maximum instantaneous powers on the order of 12 W.m-3 and 1,8 W.m-2, and current densities on the order of 25 A.m-3 et 3,8 A.m-2. An optimization work of the MFC functioning has been done. So, the conductivity increase of the anodic solution and the decrease of sediment quantity in the compost solution allowed the improvement of the electrochemical response of the anodic material and to obtain maximal instantaneous powers on the order of 17,5 W.m-3 and 2,7 W.m-2, and current densities on the order of 60 A.m-3 et 9,2 A.m-2. The limiting factor remains the electrochemical behavior of the MnOx film

Construed bachelor work features into problems hydrogen fuel articles and survey on low-temperature fuell elements with polymeric electrolyte (PEMFC). Basic sight work is study feature catalyzers on base MnOx on real fuel cell type PEMFC. Exit are then measured characteristic this way creation fuel cell.

Fuel cell´s have to function and be exploited for the purposes to dawdler were to be designed, behind achievement their requisite feature. To achievement these needs is then need use fit chemical accelerator about specific features and ensure his fit incorporated to the article. In those work in the concrete will treat of recognition feature chemical accelerator lay on in form inks obtained from powdery matters, like chemical accelerator will on used electrode aggradation MnOx. Recognition feature chemical accelerator will conducted by the help of method EQCM (Electrochemical Quartz Crystal Microbalance).

The rechargeable alkaline manganese dioxide-zinc (RAM™) battery system has been difficult to commercially develop in the past due to irreversible phase formation and progressive and cumulative capacity fade. This system has many advantages however, such as low cost and environmentally sustainable materials, long shelf life, moderate energy density, and safety. A flat-plate architecture was developed and investigated in half and full-cell apparatuses with the goal of understanding and improving cumulative capacity fade in the electrolytic manganese dioxide (EMD) cathode. Two types of cathode current collectors (CCs) were developed, a thin film foil CC and an expanded metal mesh CC and used to assess the effect of various additives over 30+ cycles under various operating conditions. Conductive carbon black (Super C65) and graphite (KS44) additives were shown to improve cell performance at 15 wt. % KS44 graphite providing an electrically conductive network between adjacent EMD particles. In addition, other chemical additives (BaSO₄, Sr(OH)₂•8H₂O, Ca(OH)₂, and Bi₂O₃) were investigated at 5 wt. % with Bi₂O₃ providing a reproducible improvement over a control recipe. Mechanical stability of the cathode electrode and pressure application were significant causes of cell failure. Slow rates of discharge, and shallow depth of discharge (DOD) charge/discharge protocols reduced capacity fade by limiting electrochemically irreversible phase formation such as Mn₂O₃, Mn₃O₄, Zn₂MnO₄, and Mn(OH)₂. Analytical characterization techniques including Scanning Electron Microscopy/ Energy Dispersive X-Ray Spectroscopy (SEM/EDS), X-Ray Photoelectron Spectroscopy (XPS), Powder X-Ray Diffraction (XRD), and Potentiostatic Electrochemical Impedance Spectroscopy (PEIS) were used to provide supporting evidence indicating that the main causes of capacity fade are linked to the cathode electrode’s mechanical properties, increased cell resistance, and progressive and irreversible phase formation.
Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate

The present work deals with the use of manganese oxide as a catalyst for positive electrode of fuel cells. The theoretical part is to analyze the problem of fuel cells, focusing on lowtemperature fuel cells. Are discussed and the methods of measurement and evaluation of properties of manganese oxide layer. The practical part deals with doping electrolytic manganese dioxide salts of divalent metals and monitoring their behavior in the cyclic voltammetry by the EQCM method.

The subject of this graduation thesis is low-cost alkaline power cells and especially electrodes with alternative catalyst made of MnOx + dopant. The thesis expands the bachelor´s thesis [1] and previous research [4] [12] [13] [14]. Volt-ampere characteristics and power characteristics of the katodes for AFC, subsidized with various dopants, are the outcome of this project. The project presents the optimalisation of preparation process of AFC electrodes. The aim is to prepair several electrodes with identical construction, which varies only with the type of the dopant.

This master thesis deals with qualifications of the catalytic materials for positive electrode low-temperature fuel cells. The teoretical part focuses on the physical and chemical properties of low-temperature fuel cells. There are described methods of hydrodynamic RDE and RRDE. RRDE study utilizes methods linear and cyclic voltammetry for qualifying performance of catalytic materials and presentation of results. The practical part describes the preparation various types of carbon materials. There are monitored the oxygen reduction using RRDE. Catalytic materials are evaluated: CV, stability, kinetic parameters, creation of intermediate H2O2 and kinetics of electrode reactions.

Master's thesis deals with new methods of preparing catalytic materials for positive electrode of an oxygen-hydrogen fuel cell and the influence of potassium permanganate or doping agent molar mass change on theirs attributes. Further it studies the use of proper measuring methods designed to qualify theirs attributes and the presentation of achieved results. In particular methods of linear sweep and cyclic voltammetry and the processing of data using Koutecky-Levich and Tafel plot and wave log analysis. Values of half-wave and onset potential and kinetic coefficient have been measured and calculated.

Genomic instability, in the form of gene mutations, insertions/deletions, and gene amplifications, is one of the hallmarks in many types of cancers and other inheritable genetic disorders. Trinucleotide repeat (TNR) disorders, such as Huntington’s disease (HD) and Myotonic dystrophy (DM) can be inherited and repeats may be extended through subsequent generations. However, it is not clear how the CAG repeats expand through generations in HD. Two possible repeat expansion mechanisms include: 1) polymerase mediated repeat extension; 2) persistent TNR hairpin structure formation persisting in the genome resulting in expansion after subsequent cell division. Recent in vitro studies suggested that a family A translesion polymerase, polymerase θ (Polθ), was able to synthesize DNA larger than the template DNA. Clinical and in vivo studies showed either overexpression or knock down of Polθ caused poor survival in breast cancer patients and genomic instability. However, the role of Polθ in TNR expansion remains unelucidated. Therefore, we hypothesize that Polθ can directly cause TNR expansion during DNA synthesis. The investigation of the functional properties of Polθ during DNA replication and TNR synthesis will provide insight for the mechanism of TNR expansion through generations.

Ce mémoire décrit la synthèse, la caractérisation – notamment thermogravimétrique et structurale – et les propriétés d'intercalation électrochimique du lithium de plusieurs types d'oxydes de manganèse. On décrit tout d'abord la préparation d'une 'ramsdellite synthétique', à faible taux de défauts structuraux de type rutile. Les oxydes de manganèse lamellaires (phyllomanganates) ont donné lieu à une nouvelle voie de synthèse du phyllomanganate de lithium par une succession de réactions topotactiques (échanges d'ions) à basse température. Sa stabilité thermique et ses propriétés d'intercalation sont examinées en comparaison avec celles du composé de sodium. La majeure partie de ce mémoire est consacrée aux spinelles Li1+xMn2–xO4, qui sont des matériaux d'électrode positive prometteurs pour les accumulateurs au lithium. Ce travail montre la faisabilité de synthèses à basse température à partir de béta-MnO2 (procédé breveté), et l'existence d'une corrélation entre température de synthèse et composition de la phase spinelle. L'intercalation du lithium est étudiée en électrolyte solide et liquide pour plusieurs compositions. L'emploi d'une cellule électrochimique in situ dans un diffractomètre de rayons X a permis de mettre en évidence le caractère biphasé de l'intercalation, même pour des spinelles de Li:Mn = 0.69. Les performances électrochimiques de spinelles substituées au magnésium et à l'aluminium sont également examinées. L'étude thermogravimétrique des spinelles Li–Mn–O a permis de mettre en évidence des réactions réversibles avec dégagement d'oxygène. Des affinements structuraux à partir de diagrammes de diffraction neutronique mettent en évidence des réactions différentes en fonction de la température d'équilibre, avec apparition de lacunes d'oxygène dans un échantillon trempé à 925°C. Enfin, un nouveau composé appelé "phase m", de formule Li0.25MnO2, a été obtenu à 150°C. Sa caractérisation structurale aux rayons X et par diffraction électronique montre qu'il s'agit d'une phase nouvelle monoclinique avec une sous-structure pseudo-hexagonale proéminente.

Ce travail consiste en l'etude de materiaux de cathode pour les piles a combustible haute temperature. Ces materiaux ont pour formule generale la1-xsrxmno3 et (la1-yyy)0,5sr0,5mno3. Dans un premier chapitre nous faisons le point sur l'etat des recherches sur les piles a combustible a oxyde electrolyte solide et leurs constituants. Le deuxieme chapitre presente la synthese des echantillons ainsi que les differents dispositifs de mesures. Le chapitre trois est consacre a la caracterisation physique et electrique des echantillons. Nous avons montre en particulier que le dopage a l'yttrium diminuait le coefficient de dilatation thermique des manganites de lanthane. Pour les echantillons exempts d'yttrium une conductivite maximale est obtenue pour x=0,55. Une etude sur la reaction de reduction de l'oxygene a l'interface la1-xsrxmno3/y2o3-zro2 est menee dans le chapitre quatre. Nous confirmons l'apparition d'un effet electrocatalytique specifique a ce materiau d'electrode. Nous apportons une contribution complementaire a la comprehension du processus d'electrode: l'echantillon qui presente la plus grande activite electrocatalytique est celui qui a la plus forte conductivite electrique. Aux faibles polarisations cathodiques, superieures a -150 mv/air, nous prouvons que l'etape limitante a lieu le long du contact triple. Aux plus fortes polarisations cathodiques nous emettons l'hypothese d'une extension progressive de la reaction sur une zone annulaire autour du perimetre de contact entre le materiau de cathode et l'electrolyte. Enfin, la surface du materiau d'electrode exposee au gaz n'est pas limitante

碩士
國立臺灣科技大學
機械工程系
106
Nowadays, manganese dioxide (MnO2) is mainly used as a catalyst in chemical reactions, such as oxygen production; or as an oxidant in an acidic solution, its characteristics have large porosity and low polarization, and can be compressed in a certain space. More manganese powder has good electrode characteristics. However, micro fuel cells have poor surface area due to very small electrode surface area. Under the condition that the surface area of the electrode is very small, carbon dioxide such as carbon black, carbon nanotubes and graphene can be mixed to improve the catalyst. And the electricity production efficiency of the air cathode. In this study, the design of single-chamber microbial fuel cell was drawn by AutoCAD software, and the microbial fuel cell was fabricated by CNC traditional milling method using acrylic as the outer casing material to improve the 3D printing used in Lin Yanting's literature [1]. The problem is leakage and cost in the technology. The carbon dioxide, carbon black, carbon nanotubes and graphite thin carbon materials were mixed by a magnet mixer, and the mixture was coated on a carbon cloth and subjected to microbial fuel cell voltage measurement and polarization experiments using an electrochemical instrument. The use of manganese dioxide to add carbon materials to improve the function of the catalyst and air cathode, in order to find the best open circuit potential value and maximum power density value, is expected to achieve the best power generation benefits. The results of this study shows that the coating of manganese dioxide on carbon cloth gives the maximum current density value of 0.523 A/m2 and the maximum power density value of 0.290 W/m2. Among the catalysts, the best effect was obtained with 50% MnO2/CNT, the open circuit potential value was increased to 0.808 V, and the maximum power density was increased to 0.694 W/m2. Keywords: single-chamber microbial fuel cell, carbon cloth modification, manganese dioxide, power generation

abstract: The fuel cell is a promising device that converts the chemical energy directly into the electrical energy without combustion process. However, the slow reaction rate of the oxygen reduction reaction (ORR) necessitates the development of cathode catalysts for low-temperature fuel cells. After a thorough literature review in Chapter 1, the thesis is divided into three parts as given below in Chapters 2-4. Chapter 2 describes the study on the Pt and Pt-Me (Me: Co, Ni) alloy nanoparticles supported on the pyrolyzed zeolitic imidazolate framework (ZIF) towards ORR. The Co-ZIF and NiCo-ZIF were synthesized by the solvothermal method and then mixed with Pt precursor. After pyrolysis and acid leaching, the PtCo/NC and PtNiCo/NC were evaluated in proton exchange membrane fuel cells (PEMFC). The peak power density exhibited > 10% and 15% for PtCo/NC and PtNiCo/NC, respectively, compared to that with commercial Pt/C catalyst under identical test conditions. Chapter 3 is the investigation of the oxygen vacancy (OV) effect in a-MnO2 as a cathode catalyst for alkaline membrane fuel cells (AMFC). The a-MnO2 nanorods were synthesized by hydrothermal method and heated at 300, 400 and 500 ℃ in the air to introduce the OV. The 400 ℃ treated material showed the best ORR performance among all other samples due to more OV in pure a-MnO2 phase. The optimized AMFC electrode showed ~ 45 mW.cm-2, which was slightly lower than that with commercial Pt/C (~60 mW.cm-2). Chapter 4 is the density functional theory (DFT) study of the protonation effect and active sites towards ORR on a-MnO2 (211) plane. The theoretically optimized oxygen adsorption and hydroxyl ion desorption energies were ~ 1.55-1.95 eV and ~ 0.98-1.45 eV, respectively, by Nørskov et al.’s calculations. All the configurations showed oxygen adsorption and hydroxyl ion desorption energies were ranging from 0.27 to 1.76 eV and 1.59 to 15.0 eV, respectively. The site which was close to two Mn ions showed the best oxygen adsorption and hydroxyl ion desorption energies improvement with the surface protonation. Based on the results given in Chapters 1-4, the major findings are summarized in Chapter 5.
Dissertation/Thesis
Doctoral Dissertation Systems Engineering 2019

The commercialization of Li-ion battery (LIB) in 1990s by Sony Corporation has led to its applications in portable electronic devices such as mobile phones, cameras, laptop computers, etc. Initially, the energy density of commercial LIB was only about 120 Wh Kg-1. However, with sustained improvements in properties of various cell components, the present-day LIB provides energy density of about 250 Wh Kg-1. With future use envisaged for mobility applications such as electric vehicles, research activities have gained momentum for development of high energy density Li-S and Li-O2 batteries. However, due to limited sources of lithium (0.007 % in earth’s crust and 0.2 ppm in sea water) and uneven distribution, concerns arise about its cost and availability which would inhibit bulk production and utilization of lithium-based batteries. Hence, there is an urgent need to switch over to battery systems employing earth abundant and environmentally benign materials. Sodium and potassium-based batteries have received attention in research laboratories as alternatives to lithium-based batteries due to their natural abundance and low cost. Na and K are the metals below Li in the periodic table and their physical and chemical properties are similar to those of Li. Na and K are the sixth and seventh most abundant elements, constituting 2.6 % and 2.4 %, respectively of the earth’s crust. Sea water contains about 10800 ppm Na and 400 ppm K. Although, the standard potentials of Na/Na+ (-2.71 V vs. standard hydrogen electrode (SHE)) and K/K+ (-2.93 V vs. SHE) are less than Li/Li+ (-3.04 V vs. SHE) by about 300 and 100 mV, respectively, the cost and availability factors overweigh the marginal reduction in energy density. The quest for new electrode materials for Na- and K-based batteries, their physicochemical characterizations and electrochemical investigations are described in the thesis. It consists of a comprehensive review of the literature on the evolution of battery systems with a focus on the next generation Na- and K-based batteries. The cathode and anode materials for Na- and K-ion batteries are reviewed along with the current research activities in Na- and K-sulphur, and Na- and K-O2 batteries. It furnishes a brief description of various experimental techniques and procedures adopted at different stages of the present thesis. The amorphous MnO2 has been prepared by two different methods: (i) reduction of KMnO4 using ethylene glycol (EG) and (ii) the redox reaction between KMnO4 and MnSO4.H2O at ambient conditions. The as prepared MnO2 samples in both cases are amorphous in nature and on heating in the temperature range of 300 – 800 °C, they convert to α-MnO2. The MnO2 prepared by reduction by EG has been studied for Na/MnO2 and Li/MnO2 laboratory scale primary cells in non-aqueous electrolytes. The specific capacity of amorphous MnO2 is 300 mAh g-1 in both Na/MnO2 and Li/MnO2 cells. Na/MnO2 cell shows a nominal voltage less than Li/MnO2 cell by 0.35 V, as expected. MnO2 prepared by the redox reaction between KMnO4 and MnSO4.H2O has a specific surface area of 184 m2 g-1 with narrowly distributed mesopores of 3.5 nm pore diameter. The crystallinity increases and specific surface area decreases upon heating. The as prepared sample provides the first discharge capacity of about 300, 200 and 80 mAh g-1 for Li-, Na- and K-MnO2 cells, respectively, at a specific current of 50 mA g-1. The attractively high discharge capacity of the as prepared amorphous MnO2 is attributed to the large specific surface area and mesoporosity. However, the crystalline samples exhibit low specific discharge capacity in comparison with amorphous samples. It deals with electrochemical impedance spectroscopy (EIS) study of Na/MnO2 primary cell fabricated in a non-aqueous electrolyte of Na salt. The EIS data provides a high resistance of Na metal due to the surface passive film. On subjecting the cell for discharge, the surface film causes a delay response of the cell voltage and the closed-circuit voltage reaches the normal discharge level following dielectric break-down of the film. The EIS data measured at different stages of cell discharge are subjected to non-linear least squares fitting with the aid of an appropriate equivalent circuit. The impedance parameters are examined to throw light on state-of-charge of Na/MnO2 primary cells. The study has been further extended to analyze the delay-time behaviour of the non-aqueous Na/MnO2 cells and quantifying the film resistance and break-down field for the film formed on the Na surface. P2-type Na0.67Mn0.65Fe0.20Ni0.15O2 is studied as a cathode material for Na-ion battery and presented. It is synthesized in microspherical and disc-like morphologies using two different synthetic procedures. Microspheres of FeCO3 are first prepared and used as a template to synthesize Mn0.65Fe0.20Ni0.15CO3, followed by its thermal decomposition to the corresponding oxide and finally, thermal fusion of the oxide with Na2CO3 to produce P2-type Na0.67Mn0.65Fe0.20Ni0.15O2. However, disc-like Na0.67Mn0.65Fe0.20Ni0.15O2 is synthesized by sintering the product obtained using a low temperature solution combustion method using aqueous solution of stoichiometric quantities of corresponding metal nitrates and sucrose as the fuel at 800 °C. Cyclic voltammograms in both the samples are characterized by well-defined two pairs of current peaks corresponding to the oxidation and reduction processes in two different stages. The sodiated microspherical oxide provides an initial discharge capacity of about 216 mAh g-1 at C/15 rate cycling with an excellent cycling stability (Fig. 3a). The rate capability is also high, and the discharge capacity is about 100 mAh g-1 at 2C rate. The high discharge capacity and high rate capability are attributed to porous microspherical morphology. When the cells with disc-like morphology cathode sample are cycled at a current density of 35 mA g-1, a specific discharge capacity of 178 mAh g-1 is obtained with close to 100 % coulombic efficiency. Capacity retention of more than 70 % is observed after 50 charge-discharge cycles Potassium tetratitanate (K2Ti4O9) is synthesized by solid-state method using K2CO3 and TiO2 and studied as an anode material for potassium ion batteries (KIB) for the first time. A discharge capacity of 97 mAh g-1 has been obtained at a current density of 30 mA g-1 (0.2 C rate) and 80 mAh g-1 at 100 mA g-1 (0.8 C rate), initially (Fig. 4a). The proposed mechanism of charging involves reduction of two Ti ions from 4+ oxidation state to 3+ oxidation state, which facilitates insertion of two K+ ions per formula unit in the zig-zag layer of TiO6 octahedra separated with K+ ions with interlayer spacing of 0.85 nm. For KIB cathode, K0.27Mn0.65Fe0.35-xNixO2 (0.00 ≤ x ≤ 0.35) is synthesized in microspherical morphology. The potassiated mixed metal oxide formed in microspherical morphology is in pure crystalline phase. The oxide with the composition x = 0.35 i.e., K0.27Mn0.65Ni0.35O2 provides the highest first specific discharge capacity of 97 mAh g-1 at C/10 rate (Fig. 4b). A good cycling stability is observed. It deals with carbonization of milk-free coconut kernel pulp carried out at low temperatures. The carbon samples are activated using KOH and electrical doublelayer capacitor (EDLC) properties are studied (Fig. 5a). Among the several samples prepared, activated carbon prepared at 600 °C has a large specific surface area (1200 m2 g-1). Cyclic voltammetry and galvanostatic charge-discharge studies suggest that activated carbons derived from coconut kernel pulp are appropriate materials for EDLC studies in acidic, alkaline and non-aqueous electrolytes. Specific capacitance (SC) of 173 F g-1 is obtained in 1 M H2SO4 electrolyte for the activated carbon prepared at 600 °C. The supercapacitor properties of activated carbon sample prepared at 600 °C are superior to the samples prepared at higher temperatures. Electrochemical studies are also undertaken for the prepared and activated samples for sodium ion intercalation/deintercalation. It is found that various factors such as surface area, mesoporosity, inter-layer spacing, electrolyte diffusion, solid electrolyte interface formation for high surface area carbon, etc. contribute to the capacity and cycle life of the material. Carbon sample synthesized at 600 °C and having a specific surface area of about 280 m2 g-1 provides the highest discharge capacity of about 200 mAh g-1 with good cycling stability. The thesis ends with a short summary and prospects of the investigations described here in. The work presented in it is carried out by the candidate as a part of Int. Ph.D. program. Some of the results are published in the literature and some more manuscripts are in preparation. A list of publications is enclosed. It is hoped that the studies reported in the thesis are worthy contributions.

碩士
國立東華大學
光電工程學系
100
Hydrogen is now considered as a charming alternative to fossil fuels. Since the environmental degradation problem and increased energy demand while reducing the fossil energy are forcing various countries to take an aggressive stance for environmental friendly alternative power source. In this study, in order to develop the bi-functional photoelectrochemical cell assembly with hydrogen/oxygen generation, we propose to establish the nano-complex photocatalyst process, MEA technology, surface modified technology, and then combine all components in photoelectrochemical cell. In first part, we propose to prepare the nano-complex MnO2 photocatalytic materials with photochemical properties and evaluate the decomposition characteristics of methylene blue in an aqueous solution under visible light irradiation in order to find the optimal prepared conditions. It is indicated that the MnO2 photocatalyst prepared with precursor of MnSO4 and (NH4)2S2O8 contains the of Pyrolusite and Ramsdellite structure. In particular, the vibration mode of the Pyrolusite and Ramsdellite structure are enhanced as precursor concentration decrease from 0.7M to 0.1M. When MnO2 prepared with precursor concentration of 0.1M under annealing temperature of 160oC, it can clearly find the diffraction profile at 2 theta of 28.68o corresponding to the B-MnO2 (110)crystalline phase as compared to the MnO2 with 0.7M prescription prepared. To further evaluate the decomposition characteristics of methylene blue in an aqueous solution under the visible light irradiation, it can be found the significant characteristics of decomposition as the introduction of 0.01g MnO2 photocatalyst. In second part, based on above discussion, the optimal condition is proposed to fabrication and integration for establishing bi-functional photoelectrochemical cell. It is found that the hydrogen generation (2260 umol/hr) of Pt-MnO2/C MEA is larger than Pt-TiO2/C MEA (1840 umol/hr), which can ascribe to the easily CO poisoning effect for Pt-TiO2/C MEA case when electrode working in MeOH environment. For PEM fuel cell test, the MEA without photocatalyst (Pt/C/Nafion 212) have maximum short-circuit current than others, and indicating the optimal hydrophobic properties and mass transfer properties of Pt/C electrode. The maximum output power is 2.2mW/cm2 corresponding to the current density of 11.2 mA/cm2. For photoelectrochemical cell test, the MEA with containing hydrophilicity and high surface energy can provide low mass transfer resistance (e.g. Pt-B-MnO2/C/ Nafion 212 MEA). Under the visible light irradiation, Pt-B-MnO2 /C/ Nafion 212 MEA show the maximum power density of 2.93 mW/cm2 corresponding to the current density of 14.78 mA/cm2.

Rechargeable Li-ion batteries and supercapacitors are the most promising electrochemical energy storage devices in terms of energy density and power density, respectively. Recently, nanostructured materials have gained enormous interest in the field of energy technology as they have special properties compared to the bulk. Commercially available Li-ion batteries, which are the most advanced among the rechargeable batteries, utilize microcrystalline transition metal oxides as cathode materials which act as lithium insertion hosts. To explore better electrochemical performance the use of nanomaterials instead of conventional materials would be an excellent alternative. High Li-ion insertion at high discharge rates causes slow Li+ transport which in turn results in concentration polarization of lithium ions within the electrode material, causing a drop in cell voltage. This eventually, leads in termination of the discharge process before realizing the maximum capacity of the electrode material being used. This problem can be addressed by decreasing the average particle size which leads to an increase in surface area of the electrode material. Nanostructured materials, because of their high surface area and large surface to volume ratio, to some extent can overcome the problem of slow diffusion of ions. Supercapacitors are electrical energy storage devices which can deliver large energy in a short time. A supercapacitor can be used as an auxiliary energy device along with a primary source such as a battery or a fuel cell to achieve power enhancement in short pulse applications. Active materials for supercapacitors are classified into three categories: (i) carbonaceous materials, (ii) conducting polymers and (iii) metal oxides. Among the materials studied over the years, metal oxides have been considered as attractive electrode materials for supercapacitors due to the following merits: variable oxidation state, good chemical and electrochemical stability, ease of preparation and handling. The performance of supercapacitors can be enhanced by moving from bulk to nanostructured materials. The theme of the thesis is to explore novel routes to synthesize nanostructured materials for Li-ion batteries and supercapacitors, and to investigate their physical and electrochemical characteristics. Chapter I is an introduction of various types of electrochemical energy systems such as battery, fuel cell and supercapacitor. A brief review is made on electrode materials for Li-ion batteries and supercapacitors, and nanostructured materials. Chapter II deals with the study of nanostrip orthorhombic V2O5 synthesized by a two-step procedure, with the formation of a vanadyl ethylene glycolate precursor and post-calcination treatment. The precursor and the final product are characterized for phase and composition by powder X-ray diffraction (XRD), infrared (IR) spectroscopy, thermal analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The morphological changes are investigated using field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HRTEM). It is found that the individual strips have the following dimensions, length: 1.3 μm, width: 332 nm and thickness: 45 nm. The electrochemical lithium intercalation and de-intercalation of nanostrip V2O5 is investigated by cyclic voltammetry (CV), galvanostatic charge-discharge cycling, galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy. Chapter III describes the synthesis of nanoparticels of LiMn2O4 by microwave assisted hydrothermal method. The phase and purity of spinel LiMn2O4 are confirmed by powder XRD analysis. The morphological studies are carried out using FE-SEM and HRTEM. The electrochemical performance of spinel LiMn2O4 is studied by using CV and galvanostatic charge-discharge cycling. The initial discharge capacity is found to be about 89 mAh g-1 at a current density of 21 mA g-1 with reasonably good cyclability. Chapter IV deals with synthesis of MoO2 nanoparticles through ethylene glycol medium and its electrochemical characterization. XRD data confirms the formation MoO2 on monoclinic phase, space group P21/c. Polygon shape of MoO2 is observed in HRTEM. MoO2 facilitates reversible insertion-extraction of Li+ ions between 0.25 to 3.0 V vs. Li/Li+. CV and galvanostatic charge-discharge cycling are conducted on this anode material to complement the electrochemical data. Chapter V reports the synthesis of nanostructured MnO2 at ambient conditions by reduction of potassium permanganate with aniline. Physical characterization is carried out to identify the phase and morphology. The as prepared MnO2 is amorphous and it contains particles of 5 to 10 nm in diameter. On annealing at a temperature > 400 °C, the amorphous MnO2 attains crystalline α-phase with a concomitant change in morphology. A gradual conversion of nanoparticles to nanorods (length 500-750 nm and diameter 50-100 nm) is evident from SEM and TEM studies. High resolution TEM images suggest that nanoparticles and nanorods grow in different crystallographic planes. The electrochemical lithium intercalation and de-intercalation of nanorods was performed by (CV) and galvanostatic charge-discharge cycling. The initial discharge capacity of nanorod α-MnO2 is found to be about 197 mAh g-1 at a current density of 13.0 mA g-1. Capacitance behavior of amorphous MnO2 is studied by CV and galvanostatic charge-discharge cycling in a potential range from -0.2 to 1.0 V vs. SCE in 0.1 M sodium sulphate solution. The effect of annealing on specific capacitance is also investigated. Specific capacitance of about 250 F g-1 is obtained for as prepared MnO2 at a current density of 0.5 mA cm-2 (0.8 A g-1). Chapter VI pertains to electrochemical supercapacitor studies on nanostructured MnO2 synthesized by polyol method. Although X-ray diffraction (XRD) pattern of the as synthesized nano-MnO2 shows poor crystallinity, it is found that it is locally arranged in δ-MnO2 type layered structure composed of edge-shared network of MnO6 octahedra by Mn K-edge X-ray Absorption Near Edge Structure (XANES) measurement. Annealed MnO2 shows high crystalline tunneled based α-MnO2 as confirmed by powder XRD pattern and XANES. As synthesized MnO2 exhibits good cyclability as an electrode material for supercapacitor. In Chapter VII, capacitance behavior of nanostrip V2O5, TiO2 coated V2O5 and nanocomposites of PEDOT/V2O5 are presented. Structural and morphological studies are carried out by powder XRD, IR, TGA, SEM and TEM. Cyclic voltammogram of pristine V2O5 shows the regular rectangular shape indicating the ideal capacitance behavior in aqueous 0.1 M K2SO4. The SC value of pristine V2O5 is found to be about 100 F g-1. Nanostrip V2O5 is modified with TiO2 using titanium isobutoxide to enhance the capacitance retention upon cycling. Only 48 % of the initial capacitance remains in the case of pristine V2O5 after 100 cycles, while TiO2 coated V2O5 exhibits better cyclability with capacitance of 70 % of the initial capacitance. The capacitance retention is attributed to the presence of TiO2 on the surface of V2O5 which prevents the vanadium dissolution into the electrolyte. Microwave assisted hydrothermally synthesized PEDOT/V2O5 nanocomposites are utilized as capacitor materials. The initial SC of PEDOT/V2O5 (237 F g-1) is higher than that of either pristine V2O5 or PEDOT. The enhanced electrochemical performance is attributed to synergic effect and an enhanced bi-dimensionality. Details of the above studies are described in the thesis with a conclusion at the end of each Chapter.

Rechargeable Li-ion batteries and supercapacitors are the most promising electrochemical energy storage devices in terms of energy density and power density, respectively. Recently, nanostructured materials have gained enormous interest in the field of energy technology as they have special properties compared to the bulk. Commercially available Li-ion batteries, which are the most advanced among the rechargeable batteries, utilize microcrystalline transition metal oxides as cathode materials which act as lithium insertion hosts. To explore better electrochemical performance the use of nanomaterials instead of conventional materials would be an excellent alternative. High Li-ion insertion at high discharge rates causes slow Li+ transport which in turn results in concentration polarization of lithium ions within the electrode material, causing a drop in cell voltage. This eventually, leads in termination of the discharge process before realizing the maximum capacity of the electrode material being used. This problem can be addressed by decreasing the average particle size which leads to an increase in surface area of the electrode material. Nanostructured materials, because of their high surface area and large surface to volume ratio, to some extent can overcome the problem of slow diffusion of ions. Supercapacitors are electrical energy storage devices which can deliver large energy in a short time. A supercapacitor can be used as an auxiliary energy device along with a primary source such as a battery or a fuel cell to achieve power enhancement in short pulse applications. Active materials for supercapacitors are classified into three categories: (i) carbonaceous materials, (ii) conducting polymers and (iii) metal oxides. Among the materials studied over the years, metal oxides have been considered as attractive electrode materials for supercapacitors due to the following merits: variable oxidation state, good chemical and electrochemical stability, ease of preparation and handling. The performance of supercapacitors can be enhanced by moving from bulk to nanostructured materials. The theme of the thesis is to explore novel routes to synthesize nanostructured materials for Li-ion batteries and supercapacitors, and to investigate their physical and electrochemical characteristics. Chapter I is an introduction of various types of electrochemical energy systems such as battery, fuel cell and supercapacitor. A brief review is made on electrode materials for Li-ion batteries and supercapacitors, and nanostructured materials. Chapter II deals with the study of nanostrip orthorhombic V2O5 synthesized by a two-step procedure, with the formation of a vanadyl ethylene glycolate precursor and post-calcination treatment. The precursor and the final product are characterized for phase and composition by powder X-ray diffraction (XRD), infrared (IR) spectroscopy, thermal analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The morphological changes are investigated using field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HRTEM). It is found that the individual strips have the following dimensions, length: 1.3 μm, width: 332 nm and thickness: 45 nm. The electrochemical lithium intercalation and de-intercalation of nanostrip V2O5 is investigated by cyclic voltammetry (CV), galvanostatic charge-discharge cycling, galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy. Chapter III describes the synthesis of nanoparticels of LiMn2O4 by microwave assisted hydrothermal method. The phase and purity of spinel LiMn2O4 are confirmed by powder XRD analysis. The morphological studies are carried out using FE-SEM and HRTEM. The electrochemical performance of spinel LiMn2O4 is studied by using CV and galvanostatic charge-discharge cycling. The initial discharge capacity is found to be about 89 mAh g-1 at a current density of 21 mA g-1 with reasonably good cyclability. Chapter IV deals with synthesis of MoO2 nanoparticles through ethylene glycol medium and its electrochemical characterization. XRD data confirms the formation MoO2 on monoclinic phase, space group P21/c. Polygon shape of MoO2 is observed in HRTEM. MoO2 facilitates reversible insertion-extraction of Li+ ions between 0.25 to 3.0 V vs. Li/Li+. CV and galvanostatic charge-discharge cycling are conducted on this anode material to complement the electrochemical data. Chapter V reports the synthesis of nanostructured MnO2 at ambient conditions by reduction of potassium permanganate with aniline. Physical characterization is carried out to identify the phase and morphology. The as prepared MnO2 is amorphous and it contains particles of 5 to 10 nm in diameter. On annealing at a temperature > 400 °C, the amorphous MnO2 attains crystalline α-phase with a concomitant change in morphology. A gradual conversion of nanoparticles to nanorods (length 500-750 nm and diameter 50-100 nm) is evident from SEM and TEM studies. High resolution TEM images suggest that nanoparticles and nanorods grow in different crystallographic planes. The electrochemical lithium intercalation and de-intercalation of nanorods was performed by (CV) and galvanostatic charge-discharge cycling. The initial discharge capacity of nanorod α-MnO2 is found to be about 197 mAh g-1 at a current density of 13.0 mA g-1. Capacitance behavior of amorphous MnO2 is studied by CV and galvanostatic charge-discharge cycling in a potential range from -0.2 to 1.0 V vs. SCE in 0.1 M sodium sulphate solution. The effect of annealing on specific capacitance is also investigated. Specific capacitance of about 250 F g-1 is obtained for as prepared MnO2 at a current density of 0.5 mA cm-2 (0.8 A g-1). Chapter VI pertains to electrochemical supercapacitor studies on nanostructured MnO2 synthesized by polyol method. Although X-ray diffraction (XRD) pattern of the as synthesized nano-MnO2 shows poor crystallinity, it is found that it is locally arranged in δ-MnO2 type layered structure composed of edge-shared network of MnO6 octahedra by Mn K-edge X-ray Absorption Near Edge Structure (XANES) measurement. Annealed MnO2 shows high crystalline tunneled based α-MnO2 as confirmed by powder XRD pattern and XANES. As synthesized MnO2 exhibits good cyclability as an electrode material for supercapacitor. In Chapter VII, capacitance behavior of nanostrip V2O5, TiO2 coated V2O5 and nanocomposites of PEDOT/V2O5 are presented. Structural and morphological studies are carried out by powder XRD, IR, TGA, SEM and TEM. Cyclic voltammogram of pristine V2O5 shows the regular rectangular shape indicating the ideal capacitance behavior in aqueous 0.1 M K2SO4. The SC value of pristine V2O5 is found to be about 100 F g-1. Nanostrip V2O5 is modified with TiO2 using titanium isobutoxide to enhance the capacitance retention upon cycling. Only 48 % of the initial capacitance remains in the case of pristine V2O5 after 100 cycles, while TiO2 coated V2O5 exhibits better cyclability with capacitance of 70 % of the initial capacitance. The capacitance retention is attributed to the presence of TiO2 on the surface of V2O5 which prevents the vanadium dissolution into the electrolyte. Microwave assisted hydrothermally synthesized PEDOT/V2O5 nanocomposites are utilized as capacitor materials. The initial SC of PEDOT/V2O5 (237 F g-1) is higher than that of either pristine V2O5 or PEDOT. The enhanced electrochemical performance is attributed to synergic effect and an enhanced bi-dimensionality. Details of the above studies are described in the thesis with a conclusion at the end of each Chapter.

碩士
國立臺北科技大學
車輛工程系所
102
According to current marketed electric scooter, the biggest problem is lack of cruising range. In the light of this, this study presents a hydrogen fuel cell hybrid range extended scooter, which consisted of 54V/24Ah Li-MnO2 battery and 200W hydrogen fuel cell. And use the wireless router to connect your tablet to make it through WiFi connection becomes monitor. This study focus on energy management system, the conversion process improvements measurement method of battery capacity (State of Charge, SOC). And write a program which update battery capacity to prevent inaccurate measurements caused by battery aging. This study designed a control system to meet the needs of actual driving. And use multi-mode and acceleration limit as an energy management strategy to reduce power output while low SOC. The experimental results show the dual power mode can reduce about 17% of battery power output, and acceleration limit can reduce to approximately 12.82% of the motor power consumption.

Lithium-ion battery is attractive for various applications because of its high energy density. The performance of Li-ion battery is influenced by several properties of the electrode materials such as particle size, surface area, ionic and electronic conductivity, etc. Porosity is another important property of the electrode material, which influences the performance. Pores can allow the electrolyte to creep inside the particles and also facilitate volume expansion/contraction arising from intercalation/deintercalation of Li+ ions. Additionally, the rate capability and cycle-life can be enhanced. The following porous electrode materials are investigated. Poorly crystalline porous -MnO2 is synthesized by hydrothermal route from a neutral aqueous solution of KMnO4 at 180 oC and the reaction time of 24 h. On heating, there is a decrease in BET surface area and also a change in morphology from nanopetals to clusters of nanorods. As prepared MnO2 delivers a high discharge specific capacity of 275 mAh g-1 at a specific current of 40 mA g-1 (C/5 rate). Lithium rich manganese oxide (Li2MnO3) is prepared by reverse microemulsion method employing Pluronic acid (P123) as a soft template. It has a well crystalline structure with a broadly distributed mesoporosity but low surface area. However, the sample gains surface area with narrowly distributed mesoporosity and also electrochemical activity after treating in 4 M H2SO4. A discharge capacity of about 160 mAh g-1 is obtained at a discharge current of 30 mA g-1. When the acid-treated sample is heated at 300 °C, the resulting porous sample with a large surface area and dual porosity provides a discharge capacity of 240 mAh g-1 at a discharge current density of 30 mA g-1. Solid solutions of Li2MnO3 and LiMO2 (M=Mn, Ni, Co, Fe and their composites) are more attractive positive electrode materials because of its high capacity >200 mAh g-1.The solid solutions are prepared by microemulsion and polymer template route, which results in porous products. All the solid solution samples exhibit high discharge capacities with high rate capability. Porous flower-like α-Fe2O3 nanostructures is synthesized by ethylene glycol mediated iron alkoxide as an intermediate and heated at different temperatures from 300 to 700 oC. The α-Fe2O3 samples possess porosity with high surface area and deliver discharge capacity values of 1063, 1168, 1183, 1152 and 968 mAh g-1 at a specific current of 50 mA g-1 when prepared at 300, 400, 500, 600 and 700 oC, respectively. Partially exfoliated and reduced graphene oxide (PE-RGO) is prepared by thermal exfoliation of graphite oxide (GO) under normal air atmosphere at 200-500 oC. Discharge capacity values of 771, 832, 1074 and 823 mAh g -1 are obtained with current density of 30 mA g-1 at 1st cycle for PE-RGO samples prepared at 200, 300, 400 and 500 oC, respectively. The electrochemical performance improves on increasing of exfoliation temperature, which is attributed to an increase in surface area. The high rate capability is attributed to porous nature of the material. Results of these studies are presented and discussed in the thesis.

Lithium-ion battery is attractive for various applications because of its high energy density. The performance of Li-ion battery is influenced by several properties of the electrode materials such as particle size, surface area, ionic and electronic conductivity, etc. Porosity is another important property of the electrode material, which influences the performance. Pores can allow the electrolyte to creep inside the particles and also facilitate volume expansion/contraction arising from intercalation/deintercalation of Li+ ions. Additionally, the rate capability and cycle-life can be enhanced. The following porous electrode materials are investigated. Poorly crystalline porous -MnO2 is synthesized by hydrothermal route from a neutral aqueous solution of KMnO4 at 180 oC and the reaction time of 24 h. On heating, there is a decrease in BET surface area and also a change in morphology from nanopetals to clusters of nanorods. As prepared MnO2 delivers a high discharge specific capacity of 275 mAh g-1 at a specific current of 40 mA g-1 (C/5 rate). Lithium rich manganese oxide (Li2MnO3) is prepared by reverse microemulsion method employing Pluronic acid (P123) as a soft template. It has a well crystalline structure with a broadly distributed mesoporosity but low surface area. However, the sample gains surface area with narrowly distributed mesoporosity and also electrochemical activity after treating in 4 M H2SO4. A discharge capacity of about 160 mAh g-1 is obtained at a discharge current of 30 mA g-1. When the acid-treated sample is heated at 300 °C, the resulting porous sample with a large surface area and dual porosity provides a discharge capacity of 240 mAh g-1 at a discharge current density of 30 mA g-1. Solid solutions of Li2MnO3 and LiMO2 (M=Mn, Ni, Co, Fe and their composites) are more attractive positive electrode materials because of its high capacity >200 mAh g-1.The solid solutions are prepared by microemulsion and polymer template route, which results in porous products. All the solid solution samples exhibit high discharge capacities with high rate capability. Porous flower-like α-Fe2O3 nanostructures is synthesized by ethylene glycol mediated iron alkoxide as an intermediate and heated at different temperatures from 300 to 700 oC. The α-Fe2O3 samples possess porosity with high surface area and deliver discharge capacity values of 1063, 1168, 1183, 1152 and 968 mAh g-1 at a specific current of 50 mA g-1 when prepared at 300, 400, 500, 600 and 700 oC, respectively. Partially exfoliated and reduced graphene oxide (PE-RGO) is prepared by thermal exfoliation of graphite oxide (GO) under normal air atmosphere at 200-500 oC. Discharge capacity values of 771, 832, 1074 and 823 mAh g -1 are obtained with current density of 30 mA g-1 at 1st cycle for PE-RGO samples prepared at 200, 300, 400 and 500 oC, respectively. The electrochemical performance improves on increasing of exfoliation temperature, which is attributed to an increase in surface area. The high rate capability is attributed to porous nature of the material. Results of these studies are presented and discussed in the thesis.

碩士
國立臺北科技大學
車輛工程系所
101
To improve the driving range, the study presents a dual power system consisted of 54V/24Ah Li-MnO2 battery and 100W hydrogen fuel cell which is additional installed for range extender. We present two power management strategies that limit speed and acceleration capability. Finally we use ECE40 cycle to validate these two way can upgrade the range of the system. Speed lamination way could add 6 km .The maximum of speed are 50km/h、40km/h、30km/h when SOC (State of Charge) are 60-100%、40-60% and 0-40%，the power of depletion from 2188W to 1270W decline margin is 42%. Acceleration capability lamination could add 0.925 km. When SOC are 60-100%、40-60% 、20-40%、0-20% the energy are 5.9kWh、5.59kWh、5.14kWh、4.55kWh. Compare these two ways speed lamination has 16.91% and acceleration capability lamination has 2.9% range extender effect.