bluuebunny/crossref_metadata_2025 huggingface dataset:
Supercapacitor Behavior of CNT/MnO2 Composite
Authors: Wei S. , Kang W. P. , Davidson J. L. , Rogers B. R. , Huang Jin-Hua
Published: October 2010

An effective technique to fabricate thin-film carbon nanotube (CNT)/manganese dioxide (MnO2) composite material is developed for electrochemical supercapacitor applications. Cyclic voltammetry and galvanostatic charging-discharging experiments indicate that this composite material demonstrates far superior capacitive properties than prestine CNTs. The chemistry of this material is confirmed with XPS.
SnO2-Modified MnO2 Electrode Materials for Electrochemical Capacitor
Authors: Chen Yatao , He Ping , Huang Ping , Wang Li , Yi Xiaofang , Dong Faqin
Published: October 2010

MnO2 was prepared by simple redox reaction and SnO2 was synthesized by sol-gel method. The structure and surface morphology of as-prepared MnO2 and SnO2 were characterized by XRD and SEM, respectively. According to different weight ratio, as-prepared samples were mixed as electrode materials. The corresponding electrochemical characteristics were evaluated by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy in KCl solution. It was shown that the as-prepared composite electrode had excellent properties in capacitance, and the specific capacitance of single electrode with 10 wt% SnO2 was up to 302.1 F g-1 at the current density of 5 mA/cm2. Furthermore, the composite electrode exhibited a very stable capacitance after repeating cycles compared to that of the separate MnO2 or SnO2 electrode. It was concluded that the doped SnO2 had positive effect on the electrochemical performance of MnO2. The composite materials of them could be potential and cost-effective electrode for electrochemical capacitor.
Hydrogen Permeation, Diffusion and Solution in LaNi5-Based Electrode
Authors: Mirkova Lidia
Published: October 2010

LaNi5 electrodes are widely used in electrochemical power sources. Such electrodes were prepared and were used as a membrane in the cell of Devanathan-Stachurski set-up. The processes of permeation, transport and solution of hydrogen in the electrodes are investigated trough analysis of permeation transients in 6M KOH. The total amount of hydrogen, permeating the electrode and the distribution of trapped hydrogen are also evaluated. The permeation efficiency of 56 % is estimated to be very high. The value of the diffusion coefficient of 5.8.10-5 cm2 sec-1 is in correlation with the literature data for similar materials. The reversible trapped hydrogen is distributed mainly in the electrode range near to the entry side of the electrode. It is shown that in spite of the complexity of such electrodes, the electrochemical permeation technique of Devanathan-Stachurski could be used for obtaining important data for hydrogen behavior in such Me-H system.
SnO2-Ionomer Composites: A Comparative Study of the Transport Properties
Authors: Mecheri Barbara , Felice Valeria , D'Epifanio Alessandra , Tavares Ana , Licoccia Silvia
Published: October 2010

Composite membranes were prepared using hydrated tin oxide as filler and either Nafion or sulfonated poly sulfone (SPS) as ionomers. The filler content ranged between 5 and 35 wt.%. The ion exchange capacity (IEC) values of the membranes, as well as their proton conductivity and water uptake properties, were determined by means of potentiometric titrations, electrochemical impedance spectroscopy (EIS) and dynamic vapor sorption (DVS). The effect of the filler on the ionomer properties was found to be strongly dependent on the ionomer microstructure. Such effect resulted to be particularly important for SPS membranes, whose proton conductivity was improved al low RH as the filler content increased.
Development of New Anion-Conducting Layered Perovskite-Type Oxide Electrolytes
Authors: Watanabe Hiroshi , Takahashi Hiroki , Takeguchi Tatsuya , Yamanaka Toshiro , Ueda Wataru
Published: October 2010

Layered perovskite oxide LaSr3Fe3O10 (LSFO) was characterized by electrochemical measurements and XRD. The H2 sensing property of the oxide with 15wt% Pd/LSFO anode catalyst in H2 at room temperature was examined. As for H2 sensing, the potential about 0.9 V was gained in the presence of H2 without cathode catalyst. Furthermore, the membrane potential for concentration cell of NaOH with LSFO showed negative value, and the potential with anion exchange membrane (AEM) also showed negative value. These results suggest that LSFO shows OH- conductivity and the possibility of a new type fuel cell by using LSFO as electrolyte.
Characteristics of Conducting Polymer-Coated Nanosized LiFePO4 Cathode in the Li+ Batteries
Authors: Dinh Hung-Cuong , Yeo In-Hyeong , Cho Won Il , Mho Sun-il
Published: October 2010

Both nano-sized and micron-sized LiFePO4 crystalline particles with rhombus structure were synthesized by a hydrothermal method for the cathode materials. Coating conductive polymers, such as polypyrrole (PPy) and poly-3,4-ethylenedioxythiophene (PEDOT), on the surfaces of LiFePO4 particles improved the battery capacities by increasing the ionic and electric conductivities of the cathode materials. The nano-sized LiFePO4 coated with PEDOT shows the largest specific capacity (167 mAhg-1 for initial to 158 mAhg-1 after 50 cycles), compared to the cases coated with PPy (165 mAhg-1 to 127 mAhg-1) and with carbon (152 mAhg-1 to 147 mAhg-1). Compared to the nano-sized particles, the micron-sized particles have much smaller surface-to-volume ratios, which resulted in increased diffusion distance requirements for lithium ions and, also, reduced accessibility of lithium ions.
The Effect of Ion-Pairing on the Open Circuit Potential of 3-Mercaptoproprionic Acid Modified Gold Electrodes
Authors: Anderson Mark R. , Harper Alice C.
Published: October 2010

Open circuit potential (OCP) measurement is used to monitor the charge of a monolayer of 3-mercaptopropionic acid. OCP is determined by the concentrations of the reduced and oxidized forms of a redox couple in the solution adjacent to the modified interface. OCP values were monitored in the presence of the one-electron redox couple Fe(CN)63-/4- as a function of solution pH. The OCP measured at basic pHs was different from the acidic OCP due to differences in electrostatic interactions between the interface and the redox species as described by the Nernst equation. The influence of ion-pairing with the monolayer is studied by varying the identity and concentration of the electrolyte cations in the solution.
Dielectric Relaxation in Dimethyl Sulfoxide/Water Mixtures
Authors: Lu Zijie , Manias Evangelos , Lanagan Michael , Macdonald Digby
Published: October 2010

Dielectric spectra of dimethyl sulfoxide (DMSO)/water mixtures, over the entire concentration range, were measured using the transmission line method at frequencies from 45 MHz to 26 GHz and at temperatures of 298-318 K. The relaxation times of the mixtures showed a maximum at an intermediate molar fraction of DMSO. A water structure "breaking effect", manifested by a reduced average number of hydrogen bonds per water molecule, was observed in dilute aqueous solutions based on the dielectric relaxation dynamics analysis. The increase in the dielectric relaxation time in DMSO/water mixtures was attributed to the spatial (steric) constraints of DMSO molecules on the hydrogen bond network, rather than being due to hydrophobic hydration of the methyl groups. The interactions between water and DMSO molecules in DMSO-rich mixtures are also discussed.
Electrodeposition of Platinum Nanowires: Electrochemical Characterization
Authors: Mahshid Sahar S. , Dolati Abolghasem , Hashemi Daryan Sahar , Ghorbani Mohammad , Ghahramaninezhad Ahmad
Published: October 2010

Platinum nanowires (PtNWs) were electrodeposited on the polycarbonate templates (PCTs) in aqueous solution of H2PtCl6 in triply distilled water. Nanowires with diameters of 50 and 100 nanometers were electrodeposited on the same condition. The kinetics of electrodeposition process was studied by electrochemical techniques such as voltammetry and chronoamperometry methods. Increasing the scan rate, the peaks shifted to more negative potentials and the current density also increased in each peak which was typical for a diffusion-control process. The potential range for the deposition of platinum nanowires was specified and consequently the potentiostatic i-t transients were utilized to produce the nanowires. Afterward, diffusion coefficient and also density of primer nuclei were then calculated by electrochemical measurements. Morphology of the nanowires was then characterized by scanning electron microscopy (SEM).
Analytical Impedance Model for Electrochemically Driven Conducting Polymer Devices
Authors: Shoa Tina , Yoo Dan S. , Fok Eddie , Madden John
Published: October 2010

An analytical model is presented to describe the electrochemical impedance of conducting polymer based devices. The analytical expression of the impedance is obtained from a two dimensional finite transmission line equivalent circuit. The model relates impedance to cell geometry, electrolyte conductivity, polymer ionic and electronic conductivities and capacitance. These parameters were measured for a hexafluorophosphate (PF6-) doped polypyrrole material (the conducting polymer used in this study) and entered to the model to predict its impedance as a function of frequency. The model is unique in representing the two dimensional charging of the polymer, namely ionic mass transport through the thickness of the polymer structure and electronic resistance along its length. Close agreement is observed between impedance spectroscopy results and model prections of the charging of a polypyrrole film electrically connected at one end. The provides a means of modeling the electrochemical charging of conducting polymers and electrochemical double layer capacitor electrodes having significant ionic and electronic conductivities.
Utilization of Electrochemical Techniques for Copper Removal, Speciation, and Analysis in Aqueous Systems
Authors: Gomes Jewel A. , Islam Kamrul , Islam Mohammad R. , Irwin George , Bernazzani Paul , Cocke David
Published: October 2010

Copper is vital for human health in minute amounts, but rapid and excessive intake of it from drinking water can cause short-term gastrointestinal disturbance. Long-term exposure to copper higher than 1.3 ppm over many years can cause kidney and liver damage. People with Wilsons disease and children under one year of age are more sensitive to copper than others. For this reason, in 1991 the U.S. Environmental Protection Agency established rules for controlling copper levels in public water supplies. Copper has long been an USEPA priority pollutant and also is an important environmental concern because of its toxicity. In the present work, electrocoagulation technique has been used to remove copper from aqueous systems using iron sacrificial electrodes, and its analysis has been performed using a relatively new nano-band electrode system, whose working principle is anodic stripping voltammetry. We optimized this analytical technique for measurement copper in water samples. The influence of deposition potential, different supporting electrolytes and mercury plating time on nano-band iridium electrodes has been investigated. The floc produced by electrocoagulation has been characterized using XRD, SEM-EDS, Moessbauer, and FTIR.
An XAFS Study of Tantalum Chloride in the Ionic Liquid 1-Ethyl-3-Methyl Imidazolium Chloride/Aluminum Chloride
Authors: Roeper Donald , Pandya Kumi , Cheek Graham T. , O'Grady William
Published: October 2010

Tantalum chloride was studied with extended X-ray absorption fine structure spectroscopy (XAFS) in acidic and basic aluminum chloride/1-ethyl-3-methyl imidazolium chloride ionic liquids (ILs). Anhydrous Ta2Cl10 is more soluble in the basic solution than in the acidic solution and the X-ray absorption data shows that the coordination shell of chlorides around the tantalum is larger in the basic solution. In the acidic solution, tantalum has five chlorides in its coordination shell while in the basic solution; the tantalum is coordinated by seven chlorides. This indicates that the Lewis acidity of the tantalum chloride causes the Ta to coordinate differently in the acidic and the basic solutions.
Interaction of Anticancer Drug Methyl Caffeate with DNA Investigated by Electrochemical and Spectroscopic Methods
Authors: Wang Wei , He Ping , Liang Yan , Chen Yatao , Xia An , Zeng Qingyou
Published: October 2010

The interaction of methyl caffeate with herring sperm DNA was investigated by cyclic voltammetry, differential pulse voltammetry and ultraviolet absorption spectrometry. Methyl caffeate had a well-defined electrochemical signal in 0.50 M acetate buffer (pH 4.6) involving two electrons and two protons. The binding of methyl caffeate to herring sperm DNA resulted in a series of changes in the electrochemical behavior, giving a considerable decrease in the peak currents and a negative shifts in the peak potential of methyl caffeate, suggesting the interaction of methyl caffeate and herring sperm DNA by an electrostatic mode. Furthermore, the data from the electrochemical investigation showed that a non-electroactive supramolecular compound was formed between methyl caffeate and herring sperm DNA. The conclusion was reinforced by ultraviolet absorption spectrometry.
Electrochemical Behavior of Esculetin on Glassy Carbon Electrode
Authors: Chen Yatao , He Ping , Liang Yan , Cheng Lanying , Xia An , Zhang Tinghong
Published: October 2010

The electrochemical behavior of esculetin was investigated by cyclic voltammetry on glassy carbon electrode. The experimental conditions, such as supporting electrolyte and pH value, were tested for the electrochemical characterization of esculetin. It was shown that, in acetate buffer, the electrochemical behavior of esculetin had good reversibility. The average peak potential of esculetin was linearly correlative with pH value of acetate buffer, indicating that proton was involved in the electrochemical process of esculetin. Furthermore, the peak current of esculetin had linear relationship with the potential scan rate, showing that esculetin presented surface confined on glassy carbon electrode. It was observed that the cathodic peak currents were linear to the concentration of esculetin in range of 5.0 × 10-6 to 4.6 × 10-5 mol L-1 (r = 0.9994, n = 10) and the detection limit was 3.8 × 10-7 mol L-1.
Simultaneous Species Determination in Industrial Solutions by Differential Alternative Pulse Voltammetry (DAPV)
Authors: Valera Jose Adolfo , Zlatev Roumen K. , Stoytcheva Margarita , Valdez Benjamin , Carrillo Monica
Published: October 2010

The Differential Alternative Pulses Voltammetry (DAPV) combining the high sensitivity of the Differential Pulse Voltammetry with the increased resolution of the second order voltammetric techniques was applied for on-site simultaneous determination of species as As(III), Pb(II) and Tl(I) in industrial solution without preliminary species separation. The limits of the species concentration ratios allowing simultaneous determination with preset precision of les than 10% were determined. The method was applied for determination in real industrial solutions.
New Amperometric Methods for the Trace Determination of Cu(II), Ag(I) and Au(III)
Authors: Khatkar Satyender P. , Langyan Dayawati , Langyan Ritu
Published: October 2010

In the present study, amperometric determination of Cu(II), Ag(I) and Au(III) was carried out. We have used thioglycolic acid (TGA) for this purpose at d.m.e. (dropping mercury electrode). We have employed 0.1M NH3 + 0.1M NH4Cl medium for Cu(II) and Au(III) and 0.1M KNO3 for Ag(I). Both cathodic and anodic titrations were carried out successfully for all the metal ions in their respective mediums. Metal species- TGA stoichiometry obtained was 1:2, 2:1 and 1:1 for Cu(II), Ag(I) and Au(III) respectively. By amperometric method, 3.18 ppm (Cu), 5.39 ppm (Ag) and 9.52 ppm (Au) and 6.35 ppm (Cu), 10.79 ppm (Ag) and 19.70 ppm (Au) were estimated in cathodic and anodic titrations respectively with high degree of accuracy. Interference of different foreign ions has also been studied.
Detection of Oxidative Stress Biomarker Homocysteine Utilizing Resonance Elastic Light Scattering
Authors: Stobiecka Magdalena , Cutler Sara , Reed Zachary , Prance Amanda , Hepel Maria
Published: October 2010

Homocysteine is a biomarker of oxidative stress and a risk factor for many disorders, including cardiovascular and Alzheimer's disease. We have investigated new methods for the development of homocysteine assays based on gold nanoparticles (AuNP) in solutions and modified solid gold piezoelectrodes. In this work, we have applied sensitive resonance elastic light scattering (RELS) and plasmonic UV-Vis spectroscopy to monitor homocysteine-induced AuNP assembly. The assembly of AuNP frameworks by covalent binding of interparticle glutaraldehyde nanobridges has been utilized for sensitive homocysteine determination. The selectivity of a glutaraldehyde crosslinking reactions toward homocysteine has been exploited to discriminate against other aminoacids. The measurements of a homocysteine adsorption on a solid Au electrode, carried out using the electrochemical quartz crystal nanogravimetry (EQCN), have shown that a multilayer film, with thickness of up to 3 equivalent monolayers, is formed in the zwitterionic pH range of homocysteine.
Theories for Predicting Reversible Potentials of Reactions on Electrode Surfaces from Internal and Gibbs Energies: Applications to ORR
Authors: Anderson Alfred B.
Published: October 2010

When I arrived at Case in January of 1979, Ernie Yeager introduced me to the oxygen cathode reaction, which was then, as now, the kinetic bottleneck for hydrogen fuel cells. Armed with a slow semiempirical quantum theory that lacked charge self-consistency, I soon found that even the dissociative adsorption of O2 on platinum surfaces could not be calculated accurately. My semiempirical band shift technique was good only for estimating electrode potential dependencies of vibrational frequencies and some dissociation processes involving adsorbed molecules. By the late 1990's, charge self-consistent calculations were at last feasible in my lab and I began using them to develop ways to calculate reversible potentials and potential dependencies of electron transfer reactions for adsorbed molecules. Sadly, Ernie passed away about the time I began making progress in understanding the oxygen reduction reaction. Here, emphasizing O2 reduction, is an overview of these quantum electrochemistry developments at Case.
A Comparative Spectroelectrochemical Study of the Redox Electrochemistry of N-(Polyvinylamine)-Substituted-o-Nitroaniline
Authors: Jbarah Abdel Aziz , Roth Isabelle , Spange Stefan , Holze R.
Published: October 2010

The electrochemistry and spectroelectrochemistry of polyvinylamine (PVAm) and N-(polyvinylamine)-substituted-o-nitroaniline at a polycrystalline gold electrode in contact with different electrolyte solutions (0.1 M HClO4 and 0.1 M KClO4) have been investigated with cyclic voltammetry and surface enhanced Raman spectroscopy (SERS). Cyclic voltammograms recorded with in acidic electrolyte solution showed formation of N-(polyvinylamine)-o-phenylenediamine in the negative going potential scan; in neutral solution reduction proceeds only to N-(polyvinylamine)-o-phenylhydroxylamine. Vibrational modes are discussed and assigned to monomer-surface interactions of adsorbates at the gold surface in both electrolyte solutions. A variety of adsorption behaviors of these polymers at a gold surface is concluded; they apparently depend on the applied electrode potential, pH of electrolyte (acidic or neutral), type and mole percentage of the o-nitroaniline moiety. The adsorption at the gold surface is strongly enhanced with 12.7 mole% of o-nitroaniline moiety, respectively, at its PVAm-backbone. The direct coordination of these polymers with the gold surface occurred via the nitro-group of the o-nitroaniline moiety and primary amino-groups located at the polymer backbone.
Binding Energy Shifts for Cu and Ag UPD on Rh(111) Determined by Online EC-XPS
Authors: Anjos Daniela , Rigsby Matthew , Wieckowski Andrzej
Published: October 2010

The nature of Cu and Ag underpotentially-deposited on Rh(111) was investigated by X-ray photoelectron spectroscopy (XPS). These underpotential deposition (UPD) systems present multipeak features, which were evaluated by cyclic voltammetry and in terms of binding energy shifts. The use of different electrolytes (sulfuric and perchloric acid) strongly affected the metallic coverage and slightly affected the UPD shifts. Through XPS, the examined surfaces were found to contain C, O, and S or Cl, which confirms the presence of anions and/or products of their reduction at the Rh(111) surface, in addition to the deposited metals. The binding energies for underpotentially-deposited Cu and Ag displayed negative shifts (to lower binding energy) with respect to both the bulk deposits and clean metal references. These negative shifts were discussed in terms of contributions from charge transfer, orbital rehybridization, and lattice strain.
Palladium Nanostructures Synthesis by Sputtering Deposition on HOPG Surfaces
Authors: Arroyo-Ramírez Lisandra , Figueroa Yaritza , Rodríguez Diego , Otaño Wilfredo , Cabrera Carlos R.
Published: October 2010

The synthesis of palladium thin films and shell nanostructures by dc-magnetron sputtering deposition on highly ordered pyrolytic graphite (HOPG) surfaces is described. Electrospun polymer fibers mats were used as templates for the Pd shell nanostructures formation. The morphology was characterized with atomic force microscopy (AFM) and scanning electron microscopy (SEM). Pd nanostructures were used as catalysts for oxygen reduction reaction (ORR). The ORR activity was evaluated in sulfuric acid and the methanol tolerance in 1 M methanol solutions saturated with oxygen. The Pd shell nanostructures have better ORR activity than Pd thin films.
Layer-by-Layer Copper Photonic Crystals for Near Infrared Spectral Region
Authors: Wu Shich-Chuan , Yang Yu-Lin , Huang Wen-Hsien , Huang Yang-Tung
Published: October 2010

We selected copper as the material to form the 3D structures with feature sizes of 0.4 μm to study its desirable optical properties at near infrared wavelengths from using the high compatible process of damascene copper interconnections technique. The reflectance and transmittance spectra of the 3D copper photonic crystals were measured with the Fourier-transform infrared (FTIR) spectroscopy and simulated with the 3D FDTD method. Through both the experimental observation and the calculation verification, the characterization of the PBG is right at near infrared wavelengths. It is worth noted that some interesting behavior were observed in the spectra and transmitting ratio under different polarization incident conditions.
Pattern Formation in Anodic Aluminum Oxide Growth by Flow Instability and Dynamic Re-Stabilization
Authors: Barkey Dale , McHugh John
Published: October 2010

The viscous flow of oxide driven by the electrostriction force during growth of anodic aluminum oxide is treated by linear stability analysis and scale analysis. It is shown that a uniform oxide film is unstable to a periodic deformation. The re-stabilization of pore growth is examined by scale analysis of the steady pore diameter. The pattern spatial period and pore radius predicted by the analysis is compared with experimental observations reported in the literature.
Room-Temperature Synthesis of Cobalt Nanoparticles in Aqueous Solution
Authors: Balela Mary Donnabelle L. , Yagi Shunsuke , Matsubara Eiichiro
Published: October 2010

A fast low-cost approach to the fabrication of metallic cobalt (Co) nanoparticles is proposed. Metallic Co nanoparticles with mean diameters of 24-112 nm are synthesized by electroless deposition (chemical reduction) in an aqueous solution at room temperature. H2PtCl6 and N2H4 are used as a nucleating agent and a reductant, respectively. The Co(II) reduction rate and the mean particles size are strongly influenced by the concentration of the nucleating agent, which are observed by in situ mixed potential measurement and electron microscopy. The mixed potential shifts negatively with increasing H2PtCl6, which results to fast reduction of Co(II) ions. Small Co nanoparticles are thus formed.
Accumulation-Mode MOSFET (AMOSFETs) Fabricated on Silicon Nanowires and Polysilicon Thin Films
Authors: Garg Pranav , Wu Jian , Fonash Stephen J.
Published: October 2010

Accumulation-mode MOSFET (AMOSFET) is an extremely simple FET configuration which can be used to fabricate high performance FETs on nanowires, nanoribbons and ultra-thin films. Unlike conventional FETs, AMOSFETs are majority carrier devices, and rely on the ability of the gate to accumulate or deplete a nanoscale thick channel region to turn the FET ON or OFF, respectively. AMOSFETs do not require heavily doped source/drain regions (no p-n junctions) or very thin gate dielectrics; this makes the device structure extremely easy and potentially inexpensive to fabricate. Our group has previously demonstrated AMOSFETs on VLS-grown SiNWs. In this report, we give an update on AMOSFET performance for devices fabricated on VLS-grown SiNWs and on polysilicon ultra-thin films as well.
Effects of Quantum Confinement on Interdependence between DOS Spectrum and C(V) Characteristic of Si Nanowire-Based MOS Structure
Authors: Ligatchev Valeri , Chin Sai Kong
Published: October 2010

Interrelation between capacitance - gate voltage [C(V)] characteristic and density-of-states (DOS) spectrum [N(E)] is analyzed using experimental C(V) data obtained from silicon-nanowire (SiNW) based metal-oxide-semiconductor (MOS) structure, solution of coupled Schrödinger-Poisson (SP) equations (with full treatment on quantum confinement) and semi-classical Fredholm integral equation (FIE) of the first kind. It is shown that FIE valid for NW-based MOS structures with NW radii a equal to or beger than 10 nm at temperature T exceeding 38 K. However, significant deviations from FIE is predicted by SP treatment for a = 5 nm and T = 5 K. Such deviation is attributed to considerable effect of quantum confinement not only on N(E) distributions, but also on fundamental statistical distribution functions of electrons.
Facile Preparation and Characterizations of Potential Low-Cost Nanostructured Materials for Energy Gas Storage
Authors: Misran Halina , Aminuddin Atiah , Mohd Zini Faizul Akmal , Singh Ramesh
Published: October 2010

Mesoporous γ-alumina with relatively high surface area of 400 m2/g and pore size of ca. 3.8 nm were successfully prepared using facile and cost-effective method employing sol-gel route at room temperature and atmospheric pressure in the presence of conventional surfactant and fatty alcohol (palm oil derived) as template. The limited amount of water gradually added during the synthesis was found to control the rapid hydrolysis rate of the alumina precursors resulting in mesoporous formation. The mesoporosity were retained when changing the surfactant to fatty alcohol. In addition, the materials porosity was made up from framework porosity as well as textural porosity given rise from the aggregations of γ-alumina nanoparticulates.
Self-Organized Titanium Oxide Nanotubes Prepared in Phosphate Electrolytes: Effect of Voltage and Fluorine Concentration
Authors: Mahshid Sara , Dolati Abolghasem , Goodarzi Mona , Askari Masoud , Ghahramaninezhad Ahmad
Published: October 2010

TiO2 a nanotube array was prepared using an anodization process. The process proceeded in a two-electrode cell containing of platinum sheet as the cathode electrode. Two phosphate-base electrolyte solutions containing different amounts of HF and NH4F were prepared. Different concentration of fluorine ions were examined in respected electrolytes. Current transient techniques were used to produce the TiO2 nanotubes at constant voltage of 18- 25V. It was revealed that anodization at 18- 22V, in so-called electrolytes would end up to nano-tubular structure. However the tubular structure prepared at 20V and from phosphate electrolyte containing of 0.5 wt% NH4F as well as 0.5 wt% HF, was recognized the best. The results were also confirmed by Scanning Electron Microscopy (SEM) images. Phase characterization of the nanotube oxide layer was carried out using x-ray diffraction (XRD) method.
Surface Alloying/Dealloying in Pb/Au(111) System
Authors: Nutariya Jeerapat , Velleuer Jonathan , Schwarzacher Walther , Vasiljevic Natasa
Published: October 2010

In this work we examined under- and overpotential deposition of Pb on Au(111) films using a combination of electrochemical, in-situ STM and surface stress measurements. The renewed interest in Pb UPD on Au(111) is motivated by unusual surface stress relaxation at partial Pb coverage, that could be explained by a transition from Pb-Au surface-alloy to Pb incommensurate overlayer structure. The aim of our work is to investigate aspects of surface alloying transformations that have not been considered in this system so far. The extended polarization and the in-situ STM results confirm surface-alloy formation and qualitatively describe related surface changes. The initial stage of Pb overpotential growth is characterised by a compressive stress evolution for a thickness of up to 15 ML. The in-situ STM shows nucleation of a bulk Pb deposit at areas of high step density. The dissolution of Pb islands reveals unexpected surface damage associated with Pb localized alloying with Au at the Pb/Au interface.
Small Scale Microbial Fuel Cells and Different Ways of Reporting Output
Authors: Ieropoulos Ioannis A. , Winfield Jonathan , Greenman John , Melhuish Chris
Published: October 2010

The present study, reports on the findings of connecting 2 stacks of 48 MFCs and the importance of maturity and acclimation for the anodic biofilms. Furthermore, an attempt is made to emphasize the importance of a universal unit for quantifying power output. Finally, this paper presents data from the smallest MFCs, specifically designed for wastewater treatment. The main aims of this study were to (1) configure a high number of small-scale MFCs (48) to run as a stack for a long period of time (2-years); (2) repeat this process with a new set of MFCs configured as a stack of equal dimensions (units) and compare individual as well as stack performances of both old and new MFC, through polarization experiments under identical conditions; (3) normalize and compare the recorded power output according to the plethora of methods reported in the literature; (4) design even smaller MFCs and investigate their performance.
Electrochemical Quartz Crystal Microbalance to Monitor Biofilm Growth and Properties during BioElectrochemical System Inoculation and Load Conditions
Authors: Brown-Malker Shelley T. , Read Sue , Rowlands Andrew , Cooper-White Justin , Keller Jurg
Published: October 2010

BioElectrochemical Systems are an emerging technology of interest. Central to the successful operation of these systems is the development of a biofilm on an electrode surface that facilitates the interaction of microorganisms capable of extra-cellular electron transfer. Porous graphite is typically chosen as the electrode material. However, other materials could contribute to a significant improvement in reactor performance. In order to evaluate these novel materials, a platform methodology is required. In this study, E-QCM-D was evaluated using a gold electrode, a mixed biofilm population and a challenging real influent (fermented solubilised sludge). The results gave real-time feedback on both the acoustic and electrochemical impedance of the working electrode, hence providing information about biofilm thickness, viscoelasticity, kinetics and mass transport. The use of E-QCM-D is novel for this field and has the potential to provide a wealth of new data to help optimise the performance of biofilms in these systems.
MFCs and Algae
Authors: Ieropoulos Ioannis A. , Greenman John , Sauer Manuel
Published: October 2010

Algae and photosynthetic bacteria may be integrated or associated with Microbial Fuel Cells MFCs in a number of different ways including: (1) use of whole (intact) or lipid-extracted lyzed cells as the primary carbon-energy source for anodic microbial metabolism; (2) use of algal cultures (with light) as cathodic oxygenators to improve output. The idea that microalgae can grow continuously producing oxygen in close proximity to a cathode, and that their cell production as biomass can be later fed to the anode as substrate, would represent an attractive self-contained autonomous system to extract useful energy from carbon dioxide and light. The aims of the present study were to investigate the suitability of processed algal by-products as suitable fuel (C-E substrate) in the anodic feedstock (at constant flow) for electricity generation and to investigate whether live algal cultures could be used as an efficient cathodic oxygenator in a self-sustaining (catholyte) circulatory system.
Redox Flow Battery for Energy Storage
Authors: Zhang Huamin
Published: October 2010

Saving fossil energy and the widespread application of renewable energy have become important strategies of world government to maintain sustainable development of the society. With the rapid development of renewable energy (such as solar and wind energy) and the pushing forward of smart grid, large-scale and high-efficiency energy storage technology is urgently needed to remove the random and intermittent natures of the renewable energy and increase the compatibility of the renewable energy to the grid. The vanadium redox flow battery (VRB) becomes one of the most promising technologies with advantages of long cycle life, high energy convention efficiency, flexible system design, deep-discharge capability and low cost. In this paper, current progress on the VRB technology and the work undertaken by DICP will be described in detail.
A Laboratory Experiment with PEMFC Oriented towards Evaluation of the Fuel Cell for Failure Analysis in Automobiles
Authors: Santhanam Kalathur S. , Kalra N. , Hill T. , Stephenson J. , Wahila M.
Published: October 2010

An improvised laboratory experiment has been designed to evaluate the polymer electrolyte membrane fuel cell (PEMFC) under different conditions such as in resting and flooding situations. The voltage and power output of the fuel cell are dependent on the state of the membrane. The experiments are simulated for failure analysis in automobiles when flooding were to occur during the operation.
Cycle Life Prediction of Battery-Supercapacitor Hybrids Using Artificial Neural Networks
Authors: Weigert Thomas J. , Tian Qifeng , Lian Keryn K.
Published: October 2010

The cycle life of batteries and battery-supercapacitor hybrid systems was predicted using artificial neural networks. The presented techniques are able to predict the cycle life of a device based on a short (around 4% of the average cycle life) initial segment of the discharge curve. The prediction showed good performance with a correlation coefficient above 0.95. We were able to improve the predication further by considering ready measurements about the device and usage.
Development of a New Nanoscale Electrochemical Method Using Scanning Tunneling Microscopy
Authors: Honbo Kyoko , Mabuchi Katsumi
Published: October 2010

A new in-situ measurement technique for analyzing corrosion of the submicron level area in liquids was developed. In this technique, after topography is measured with a scanning tunneling microscope (STM), the measurement mode is switched and electrochemical measurements such as cyclic voltammetry are conducted by using the STM probe as a working electrode. The distance between the probe and the material is separated up to the distance where the tunneling current does not flow. The valency, concentration, and species of dissolution ions from metal can be inferred according to potential and the current density of the reduction peak of a cyclic voltammogram. We report the corrosion behavior of copper minuteness wiring using the new technique.
Electrochemical Performance of Nanoscaled La0.6Sr0.4CoO3-δ as Intermediate Temperature SOFC Cathode
Authors: Hayd Jan , Guntow Uwe , Ivers-Tiffée Ellen
Published: October 2010

Low-temperature operation (400 to 600 ºC) of solid oxide fuel cells has generated new concepts for materials choice, interfacial design and electrode microstructures. Nanoscaled and nanoporous La0.6Sr0.4CoO3-δ thin film cathodes (film thickness ~200 nm, grain size 15 - 150 nm, porosity {less than or equal to} 30 %) were derived from metal-organic precursors. A variation of calcination temperature and time made it possible to study the influence of electrode microstructure on electrochemical performance. Area specific polarization resistances as low as 0.023 Ω.cm² at 600 ºC were measured applying electrochemical impedance spectroscopy in a broad range of temperatures (400 to 600 ºC) and time (up to 300 h). These low resistance values were on the one hand facilitated by a substantial increase of the inner surface area of the porous thin film cathode. On the other hand, a significantly enhanced surface exchange was determined for nanoscaled La0.6Sr0.4CoO3-δ cathodes prepared by metal organic deposition.
Impedance Modeling of Solid Oxide Fuel Cell Cathodes
Authors: Mortensen Jakob E. , So̸gaard Martin , Jacobsen Torben
Published: October 2010

A 1-dimensional impedance model for a solid oxide fuel cell cathode is formulated and applied to a cathode consisting of 50/50 wt% strontium doped lanthanum cobaltite and gadolinia doped ceria. A total of 42 impedance spectra were recorded in the temperature range: 555-852°C and in the oxygen partial pressure range 0.028-1.00 atm. The recorded impedance spectra were successfully analyzed using the developed impedance model in the investigated temperature and oxygen partial pressure range. It is also demonstrated that the model can be used to predict how impedance spectra evolve with different physical parameters such as the cathode thickness.
Validation of the Simple Infiltrated Microstructure Polarization Loss Estimation (SIMPLE) Model Using Single Layer, Nanocomposite Sm0.5Sr0.5CoO3-x - Ce0.9Gd0.1O1.95 Solid Oxide Fuel Cell Cathodes
Authors: Nicholas Jason D. , Barnett Scott A.
Published: October 2010

Single-layer nano-composite Sm0.5Sr0.5CoO3-x (SSC) - Ce0.9Gd0.1O1.95 (GDC) Solid Oxide Fuel Cell (SOFC) cathodes with various SSC loading levels were prepared through multiple nitrate solution infiltrations. Microstructural analyses indicated that the average infiltrate hemispherical particle radius remained roughly constant, at 25nm, across multiple infiltrate-gel-800oC fire sequences. Symmetric cell polarization resistance measurements of cathode performance showed that the Simple Infiltrated Microstructure Polarization Loss Estimation (SIMPLE) model, which accounts for electrical losses associated with surface oxygen incorporation and bulk oxygen transport, was able to predict the performance of heavily infiltrated cathodes to within 55% (without the use of fitting parameters) at all temperatures from 400-700oC. Results also indicate that electronic conduction losses limited the overall cathode performance at low and medium SSC infiltrate loading levels.
Oxygen Reduction at the Surface and the Hetero-Interface of La-Sr-Co-O-Oxides
Authors: Unemoto Atsushi , Nagao Kazuki , Tairako Toshiya , Amezawa Koji , Kawada Tatsuya
Published: October 2010

To date, we have reported that oxygen surface exchange is enhanced along the hetero-interface consisting of (La,Sr)2CoO4 and (La,Sr)CoO3. However, there still remain questions on the detailed mechanisms. In this study, we examined how the composition of porous (La,Sr)2CoO4, fabricated on (La,Sr)CoO3 film, affects the enhancement. Layered electrodes consisting of porous (La1-xSrx)2CoO4{plus minus}δ (x = 1.0 and 0.8) and La0.6Sr0.4CoO3-δ were prepared and tested by impedance spectrometry. Regardless of the La/Sr ratio in (La,Sr)2CoO4 phase, the area specific conductivity was modified at lower temperatures and in higher oxygen partial pressures while the degree of the enhancement was independent of La/Sr ratio. La0.6Sr0.4CoO3-δ film electrode degraded. Composition analysis of the film surface suggested that it had precipitates such as Sr- and Co-oxides. On the other hand, when porous (La,Sr)2CoO4 was fabricated on La0.6Sr0.4CoO3-δ film, surface precipitates disappeared. This suggested that the (La,Sr)2CoO4 phase plays an important role to keep the composition of La0.6Sr0.4CoO3-δ film to be a perovskite structure possibly by accepting and/or releasing cations near the hetero-interface, resulted in the modification of the electrode performance.
Oxygen Surface Exchange and Bulk Diffusion Coefficients Evaluated from Porous Mixed Ionic-Electronic Conducting Cathodes
Authors: Endler Cornelia , Leonide André , Rüger Bernd , Weber André , Ivers-Tiffée Ellen
Published: October 2010

(i) Oxygen Surface Exchange kδ and (ii) Bulk Diffusion Coefficients Dδ of a porous La0.58Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode are determined by electrochemical impedance measurements on anode supported solid oxide fuel cells. The cathode polarization resistance of anode supported cells was separated by the method of distribution of relaxation times (DRT) followed by a CNLS fitting approach using a reasonable equivalent circuit consisting of four physical related elements. The values for kδ and Dδ were determined for cathodes fresh from the start of the cell operation up to 700h and compared to literature data on bulk samples. At an operation temperature of T = 750°C the cathode polarization resistance changed substantially with time and ended with an overall increase of 310%. The analysis of the cathode polarization resistance which was described by a Gerischer element revealed a rather constant value for kδ but a distinct decrease for Dδ.
Microstructure-Electrical Properties of Original LSCF Films Deposited by ESD for IT-SOFCs
Authors: Marinha Daniel , Dessemond Laurent , Djurado Elisabeth
Published: October 2010

Original and different microstructures of La0.6Sr0.4Co0.2Fe0.8O3-x (LSCF) films were successfully deposited by electrostatic spray deposition (ESD) varying the process conditions. The correlation between deposition parameters and resulting morphology is discussed in detail. SEM/EDS analyses have shown that large arrays of different LSCF film microstructures were obtained, ranging from dense to reticulated to porous, with thicknesses ranging from 3 to 10 µm. Single phased LSCF with typical perovskite structure, were successfully deposited for the first time by ESD on CGO substrates. ASR values of 0.8 ohm.cm² for porous films were determined from impedance spectroscopy measurements at 600 ºC. This paper successfully shows that electrochemical performances are strongly dependent on the cathode microstructure for a fixed composition.
Influence of Electrode Morphology on Electrochemical Response of SOFC Cathodes
Authors: Kreller Cortney R. , Drake Melanie E. , Adler S.
Published: October 2010

Using finite element calculations, we have investigated theoretically the role of electrode microstructure on the rate of O2 reduction in mixed conducting solid oxide fuel cell (SOFC) cathodes. These calculations were used to predict both impedance and nonlinear higher order harmonic response of single-phase electrodes having idealized 3-D microstructures based on cylinders necked spheres. These calculations show that impedance shape and higher harmonic response are generally very sensitive to the exact details of the microstructure near the electrode/electrolyte interface, even when gradients extend far beyond the interface. In contrast, microstructural details further than about one particle diameter from the interface can be accurately modeled using a macrohomogeneous (average property) description.
Increase of Anode Performance of SOFC by Reverse Current Treatment
Authors: Klotz Dino , Butz Benjamin , Leonide André , Gerthsen Dagmar , Ivers-Tiffée Ellen
Published: October 2010

The electrochemistry in the anode functional layer is still one of the performance limiting factors for the standard planar anode-supported SOFC (ASC). In this contribution we present an effective method for the improvement of anode performance. It is based on a short-time application of a high current density in reverse direction (reverse current treatment, RCT). The measured impedance data sets show a progressive decrease of the overall area specific polarization resistance (ASRpol), when the ASC is exposed to a series of RCT. The change in ASRpol could be attributed to the electrochemical polarization loss in the anode functional layer (AFL), which was reduced by 40 %. Post-test analysis with FIB/SEM revealed the formation of a nanoscaled and highly porous Ni/YSZ layer between electrolyte (YSZ) and anode (Ni/YSZ). The hereby increased length of the electrochemically active triple phase boundary (TPB) is regarded to be the cause for this distinct improvement.
Effect of Ni-GDC AFL Composition on Performance of IT-SOFCs
Authors: Lee Kang Taek , Vito Nicholas J. , Camaratta Mattehw , Yoon Hee Sung , Wachsman Eric
Published: October 2010

Anode supported solid oxide fuel cells (SOFCs) with various NiO content in the anode function layer (AFL) were fabricated and investigated. For AFLs with lower NiO content, the observed open circuit potential was higher. However, the highest maximum power density of 1.15 W/cm2 at 650 °C was achieved at 60 wt% of NiO in the AFL, which is a 1:1 volume ratio of Ni to GDC phase. The optimal composition was valid in the intermediate temperature range from 450 to 650 °C. The effect of the optimal composition on power density was retained for 200 hours with high power density of 1.1 W/cm2. Electrochemical impedance tests supported this result by showing the lowest electrode area specific resistance at 60 wt% NiO, which has a linear relationship with maximum power density.
Thermodynamic Reconsiderations on Electronic Properties of Pure- and Doped-Ceria
Authors: Yokokawa Harumi , Xiong Yue-Ping , Kishimoto Haruo , Yamaji Katsuhiko , Brito M. E. , Horita Teruhisa
Published: October 2010

Reconsiderations have been made on the electronic properties of pure- and doped ceria on the basis of the energetic scheme which has been considered to take into account the regularity of the hole conductivity in rare earth doped ceria as well as the anomalous behavior of hole conductivity of nano-derived Gd-doped ceria; this assumes the constituent of Ce3+O2-O-, in other words, the electron-pair formation. To interpret the plateau found in our recent experiment on electron conductivity of pure ceria, the electron concentration has been calculated for the formation of electron-hole pairs with those data for Ce3+O2-O-. Calculated electron concentrations can reproduce essentially the same behavior as those in electron conductivity. Further considerations have been made on why the anomalous hole conductivity appeared only when the nano-powder derived GDC samples were polarized.
Electrochemical Removal of NOx-Gasses by Use of LSM-Cathodes Impregnated with a NOx Storage Compound
Authors: Traulsen Marie L. , Kammer Hansen Kent
Published: October 2010

Electrochemical decomposition of NO on La0.85Sr0.15MnO3-δ- Ce0.90Gd0.10O1.95electrodes with and without KNO3 impregnation is investigated. The KNO3 is added as this compound is expected to work as a NOx-storage compound. Measurements are made in the temperature range 300-400 degree C and in three different atmospheres: 1000 ppm NO, 10% O2 and 1000 ppm NO + 10% O2. Electrochemical impedance spectroscopy and cyclic voltammetry are used for electrochemical characterization of the electrodes, and the conversion of NO and O2 is measured on a mass-spectrometer. The results show a significant increase in the NO-conversion, when KNO3 is added to the La0.85Sr0.15MnO3-δ- Ce0.90Gd0.10O1.95electrodes.