bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct Evaluation of O2-Reduction-Based H2O2 Generation at Pt/C-Containing Powder Microelectrode Using Scanning Electrochemical Microscopy
Authors: Umeda Minoru , Inoue Mitsuhiro , Shironita Sayoko
Published: March 2011

The percentage of H2O2 during oxygen reduction reaction (ORR) at practical powder electrocatalysts have been evaluated using a scanning electrochemical microscopy (SECM). We employed a porous microelectrode which contains the electrocatalysts of Pt/C, Pt-Co/C, and Pt-Ru/C as the oxygen reduction electrode of the SECM. And the Pt microelectrode was used as the H2O2 detector. First, the H2O2 generation amount at Pt/Cs has been measured by changing the Pt loading amount. A higher Pt loading Pt/C possesses a higher ORR activity and generates a larger amount of H2O2. However, the percentage of H2O2 generated with respect to the ORR is the same irrespective of the Pt loading amount. Next, H2O2 generations have been drastically suppressed at the Pt-Co/C and Pt-Ru/C in the potential ranges of practical fuel cell cathode and anode, respectively. This explains that the used Pt-Co/C is effective when used as a cathode; and, the anode Pt-Ru/C enables to reduce the H2O2 generation even if O2 crossleak occurred in the practical PEFC.
Local In-Situ Analysis of PEM Fuel Cells by Impedance Spectoscopy and Raman Measurements
Authors: Gülzow Erich F. , Schulze Mathias , Friedrich Andreas K. , Fischer Peter , Bettermann Hans
Published: March 2011

An understanding of the processes inside of low temperature fuel cells on a local scale is required for an effective improvement strategy. For this purpose in situ Raman spectroscopy and local impedance spectroscopy is being developed. The contribution describes the modifications to the cell, and installations of additional devices and the experimental detection systems for integrating both methods into a single cell set up. First results to verify the combined results were carried out and are presented. In the case of the local impedance with segmented cells the additional effort for the simultaneous frequency analysis of all segments is described. The Raman signals of hydrogen, oxygen and water from the channels of the flow field are shown and first measurements of gas composition along the fuel path are analyzed.
A New Membrane Electrode Assembly for Low-Temperature PEM Fuel Cells Having a Nanocomposite Catalyst Layer
Authors: Dvorak David , Shahinpoor Mohsen
Published: March 2011

Studies are currently underway to manufacture a novel membrane electrode assembly (MEA) for polymer electrolyte fuel cells. This MEA will be designed to incorporate a nanocomposite catalyst layer comprising a functionally graded distribution of Platinum nano particles chemically embedded near boundaries and surfaces of the polyelectrolytic membrane. The process involved is called a REDOX operation in which first the ionic polymer membrane is oxidized with a catalyst metal. After oxidation, the ionic polymer is reduced to create functionally-graded conductor composite and near boundary porous electrodes. Initial performance tests of fuel cells incorporating these membranes show promising results which will serve as a baseline for further process optimization.
AQUIVION - The Short-Side-Chain PFSA for Next Generation PEFCs Presents D79-20BS as New Stabilized Low-EW Dispersion grade
Authors: Gebert Matthias , Merlo Luca , Arcella Vincenzo
Published: March 2011

Solvay Solexis has expanded its low-EW PFSA ionomer portfolio with a new grade. AQUIVION{trade mark, serif} is a copolymer produced from C2F4 and the co-monomer C2F3-O-(CF2)2-SO2F and represents the long-term commitment of Solvay Solexis to the emerging PEFC industry. The very short and light side chain which carries the functional SO3H group incurs a number of advantageous factors. Customers such as MEA producers enjoy benefits from the short side chain when using the various AQUIVION{trade mark, serif} membrane and dispersion grades. Both membranes and dispersions are vital for the manufacturing for Polymer Electrolyte Fuel Cell (PEFC) stacks as well as other applications such as gas humidifiers and filtration devices. The paper describes the portfolio of enhanced technical and operational characteristics resulting from use of D79-20BS dispersion.
New Approaches to Non-PGM Catalysts through Rational Design
Authors: Liu Di-Jia , Goenaga Gabriel , Ma Shengqian , Yuan Shengwen , Shui Jianglan
Published: March 2011

The catalytic oxygen reduction reaction (ORR) at the cathode represents the rate-limiting step in the overall electrocatalytic process inside of a proton exchange membrane fuel cell (PEMFC). The platinum group metals (PGMs) are current materials of choice for the cathode catalyst. Their high costs and limited reserves pose a significant challenge in implementing PEMFC for broad base commercial application. In this report, we discuss some of our recent activities in developing non-PGM electrocatalysts using rational design and synthesis approach. A variety of porous organic materials were developed as the catalyst precursors for the preparation of ORR catalysts with high surface area and active site density free of additional carbon support. Electrocatalytic activity and physical property of the new catalysts were investigated by various techniques in an attempt to understand the process of the active site formation.
Evaluation of a Self-Water Management Type of MEA in PEFC
Authors: Yamamoto Hiroyuki , Yamauchi Makoto , Doi Hirotaka , Sugiura Kimihiko
Published: March 2011

Polymer electrolyte fuel cells (PEFCs) have water management issues, such as flooding and plugging, where condensate blocks the pores of the gas-diffusion layer (GDL) and gas channels, respectively. We confirmed through visualization of the cell that the flooding/plugging phenomena in the anode gas channel occurs during low humidity conditions, when it is necessary for water to be transported from the cathode to the anode through the membrane. We developed the self-water management type of the membrane electrode assembly (MEA). The self-water management MEA was designed by combining GDLs with different properties. A GDL with high drainage properties was arranged in the gas inlet, where the electrochemical reaction was active, and a GDL with high hydration properties was arranged in the gas outlet. As a result, the cell performance was improved by using two types of GDLs with different properties.
Acceleration Test on SO2 Poisoning of Sm0.5Sr.0.5CoO3 Cathode
Authors: Yamaji Katsuhiko , Kishimoto Haruo , Horita Teruhisa , Yokokawal Harumi , Akikusa Jun , Kawano Mitsunobu
Published: March 2011

Acceleration test on the SO2 poisoning of SSC cathode was calculated by increasing the feeding rate of SO2 using 1 ppm SO2 - air mixture. The estimated degradation rate due to the SO2 poisoning was 0.05 % / 1000 h at T = 1073 K if we assumed that 1ppb SO2 existed in the ambient air.
Demonstration of Principle of Electrical Power Generation at High Fuel Utilization Efficiency by an SOFC System with an Anode Recycle Line
Authors: Watanabe Kimitaka , Yokoo Masayuki , Hayashi Katsuya , Arai Hajime
Published: March 2011

We show electric power generation of 380 W with fuel utilization of 90% using an anode recycle system, methane as fuel, and air as oxidant at a voltage of 7.5 V, which was approximately the same as that obtained with the anode recycling with fuel utilization of 80%.
Optimization of Gasifying Agent Composition in Molten Salts Gasification of Soy Sauce Cake for Molten Carbonate Fuel Cell System
Authors: Yamanaka Masao , Sugiura Kimihiko
Published: March 2011

Global warming has been a problem not only for advanced country, but also for developing country since COP15 was held. There-fore, R&D of clean energy like fuel cells is accelerated drastically. Meanwhile, the disposal of soy sauce cake is also important issue in Japan because it has rich sulfur and chlorine. There¬fore, we propose the gasification system of the soy sauce cake using molten salt. Moreover, this gasification gas is used as a fuel gas for MCFC which use same molten salts as an electrolyte. This paper elucidates about the fundamental gasification characteristics of soy sauce cake by optimizing the gasifying agent gas composition, and examines the influence of the gasification gas on the MCFC characteristic. As a result, the gasification is promoted when air is mixed with the gasifying agent, because molten salts temperature and the reactivity between soy sauce cake, gasifying agent and molten salts elevate.
Modeling of Pressurized Electrochemistry and Steam-Methane Reforming in Solid Oxide Fuel Cells Using Star-CD
Authors: Ippolito James , Recknagle Kurtis
Published: March 2011

Presented is an interesting and substantive paper in the development of effective CFD models. The paper presents a fully three-dimensional, computational fluid dynamics (CFD) study, using STAR-CD, to understand the effects of pressurization on electrochemical performance for planar solid oxide fuel cells. The CFD study considers two cases (1) a single-cell SOFC with methane as part of the fuel composition and (2) a sixteen-cell SOFC without methane in the fuel. Pressurized operation boosts electrochemical performance, alters the kinetics of methane reforming, and affects the equilibrium composition of methane fuels. The authors of this paper illustrate this from these two cases.
Exergetic Efficiency Rate of Change and Fuel Cell Degradation
Authors: Williams Mark , Suzuki A. , Miyamoto A.
Published: March 2011

The use of exergetic efficiency rate of change to evaluate fuel cell performance is developed and explained. It is important to understand the possible thermal efficiency a fuel cell system is capable of obtaining on a fuel and then what of this efficiency it actually achieves. The exergetic efficiency rate of change, is a natural and instantaneous measure of the change in fuel cell performance occurring at any time. There are three central performance measures for fuel cells. The first is exergetic efficiency which is measured by thermal efficiency. It permits the direct comparison of the performance of all fuel cell types operating on the same fuel, if desired. The second is exergetic efficiency rate of change which is useful in evaluating degradation which is the rate of change of ASR. The rate of change of exergetic efficiency is an effective way to directly relate degradation to fuel cell thermal efficiency. The third is power or power density which can be related to the economic viability of the fuel cell or fuel cell system.
Parametric Study of a PEM Fuel Cell with a Thin-Film Agglomerate Model
Authors: Lee Chun-I , Jung Shiqah-Ping , Shiu Huan-Ruei , Chang Wen-Chen , Cheng Chin-Hsiang
Published: March 2011

A one-dimensional, two-phase, steady-state, multi-component transport as well as electrochemistry behavior mathematic model of a PEM fuel cell cathode is presented in this study. The catalyst layer structure is considered to be a cylindrical thin-film agglomerate. The objective of the study is to investigate the effects of the cell performance under different design parameters, such as platinum loading, radius of catalyst pellet, Nafion film thickness, catalyst layer thickness, and porosity of catalyst layer. Results of this model was agreed reasonably with the numerical modeling and experimental data of Lin et al. In addition, the electrochemical transport phenomena, such as oxygen concentration, water concentration, water saturated, and ionic potential, were examined. The parametric analysis reveals the important role of transport mechanism in catalyst layer and our results provides useful information on the electrode design parameters of PEM fuel cells for the MEA manufacturer.
The Efficiency Evaluation of Promoting Fuel Cell Scooter in Taiwan
Authors: Tso Chunto , Chang Shinchih
Published: March 2011

This program collect and analyze other countries' practice reports for Taiwan's reference and employ TIER's model that access strategies of economic, environment and energy (3E) to analyze the prospective efficacy in Taiwan's real GDP, trade terms, export and import economy, related industries' output, the cut in CO2 emission and the overall development of fuel cell scooter industry.
Combined Electric Power and Carbon-Dioxide Separation (CEPACS) Technology
Authors: Ghezel-Ayagh Hossein , Sanderson Robert , Hunt Jennifer , Walzak Jim , Patel Dilip
Published: March 2011

FuelCell Energy, Inc. has developed novel system concepts for separation of carbon dioxide from greenhouse gas emission sources, using its patented Direct FuelCell® (DFC®) technology. DFC is based on carbonate fuel cells featuring internal reforming. The unique chemistry of carbonate fuel cells offers an innovative approach for separation of CO2 from fossil-fuel power plant exhaust streams (flue gases). DFC-based CO2 separation systems are suitable for many types of coal-based power plants, from existing pulverized coal-fired boiler steam cycle plants to future integrated gasification combined cycle plants. The carbonate fuel cell system also produces electric power at high efficiency. Cost of electricity analysis of the DFC system indicates that the simultaneous generation of power and CO2 capture is an attractive scenario for re-powering the existing coal-fueled power plants.
Direct Fuel Cell Experience on Renewable Biogas
Authors: Farooque Mohammad , Daly Joe , Leo Tony , Pais Chris , Venkataraman Ramki , Wang Jin-Yun
Published: March 2011

FCE (FuelCell Energy, Inc.) in Danbury, CT currently offers three commercial products; the DFC300MA, DFC1500, and DFC3000, rated 300 kW, 1200 kW and 2400 kW, respectively to operate on methane-rich fuels including bio-gas. These products use the Direct FuelCell® (DFC®), which has the special ability to generate electricity directly from a hydrocarbon fuel by reforming it inside the fuel cell and supplying hydrogen for fuel cell reactions. Biogas, which is available from distributed sources, contains 50-80% methane depending on the source, and is an excellent fuel for DFC power plants. FCE has placed over twenty biogas units ranging from 250 kW to 1.2MW around the world, achieving an electricity conversion efficiency of 45 to 49% (LHV). A unique feature of the DFC is that its performance is not impacted by the bio fuels diluted with CO2 (20-50%). In fact, the biogas plants are consistently showing a higher fuel cell conversion efficiency (~1% on a normalized basis) compared to pipeline natural gas plants. Initial DFC biogas applications focused on wastewater treatment, food processing and brewery industries where the contaminants are primarily sulfur and siloxane. FCE has used operation experience with these plants to improve the gas supply reliability, understanding of the biogas contaminants and improve removal process effectivity.
Fuel Cells For Aircraft Applications
Authors: Renouard-Vallet Gwenaelle M. , Kallo Josef , Friedrich Andreas K. , Schirmer Johannes , Saballus Martin , Schmithals Gerrit
Published: March 2011

Fuel Cell systems as power sources are a promising solution on board of commercial aircraft or motor glider aircraft. As well as power, fuel cell system can be a source of additional functionalities as inert gas and water provision for on-board purposes. This paper presents an overview of most of the progresses of the last past year to evaluate and demonstrate fuel cell design and capabilities on cruise and on ground operation. These results are really useful to for the possible future integration of fuel cell systems in new aircraft generation. Demonstration means like test platforms and tests results are shortly described as well as the way forward.
International Graduate Education in Fuel Cells and Hydrogen Energy in Iceland
Authors: Dvorak David , Sigfusson Thorsteinn I. , Gunnarsson Bjorn
Published: March 2011

The country of Iceland has become a world leader in renewable energy production based on the effective utilization of its natural resources. Iceland also articulated a vision of the "hydrogen economy" as a way to further reduce the import of fossil fuels. Iceland's practical experience with hydrogen and fuel cells has seen broader impact through international demonstration projects and educational programs. This paper describes the creation and execution of a MS curriculum in Hydrogen and Fuel Cells that has been operating in Iceland since 2008. It is intended for students with strong backgrounds in engineering or physical sciences, and is open to students worldwide. The program is a part of RES | the School for Renewable Energy Sciences, located in Akureyri, Iceland, and is supported by the University of Iceland and the University of Akureyri. A number of academic institutions and research establishments around the world partner in this work.
Fuel Cells And Hydrogen For Smart Grid
Authors: Patel Pinakin , Jahnke Fred , Lipp Ludwig , Abdallah Tarek , Josefik Nicholas
Published: March 2011

Fuel cells and hydrogen can play an important role in the rapidly emerging smart grid. The "soft" wind power can be converted to "hard", reliable utility power by using high temperature stationary fuel cells to co-produce baseload power plus hydrogen, and use of lower temperature fuel cells operating on hydrogen for the load following/peak power (DFC-H2® Peaker). If the stationary fuel cell operates on biogas, the hydrogen will be considered renewable and the overall system will be truly renewable power system. Demonstration of some of the major components of such as system is ongoing. A DFC-H2® plant in California has co-produced 125 kg/day of hydrogen and 250 kW of power, with a combined hydrogen, power and heat efficiency of 80-85% and ultra-low emissions. The DFC power plants currently installed or on order can support hardening of 500 MW of wind power.
Gain Scheduled Decoupled Control of CPOX Reformer for Solid Oxide Fuel Cell
Authors: Adhikari Puran , Abdelrahman Mohamed
Published: March 2011

This paper presents a unique blend of decoupled control for a catalytic partial oxidation reformer with a gain scheduler. Hydrogen output and temperature of the reformer are considered as the performance variables to be controlled. The decoupled controller designed from the linearized transfer function shows that the two outputs can be controlled with minimum loop interactions. The nonlinearity occurring at different flow rates (or power levels) is solved using the gain scheduler. The simulation results show that a superior performance can be achieved through all the levels of flow rates using the combination of a gain scheduler and the decoupled controller.
Monitoring Reactions in Alkaline Direct Ethanol Fuel Cells Assembled with Non-PT-Catalyst
Authors: Gülzow Erich F. , Beyer Monique , Friedrich Andreas K. , Pengel Stefanie , Fischer Peter , Bettermann Hans
Published: March 2011

This contribution shows how Raman spectroscopy can be used to pursue chemical reactions within fuel cells. For this, the oxidation of ethanol occurring in an alkaline direct ethanolic fuel cell was investigated. The analysis of a sequence of Raman spectra recorded during the reaction shows that ethanol was solely oxidized to acetate in a unique reaction.
Design of the Air Flow Path in Bellows-Type DMFC Based on the Three-Dimensional Simulations
Authors: Imai Tataunori , Yachi Yoshiaki
Published: March 2011

The direct methanol fuel cell (DMFC) has been paid attention for mobile devices power supply. We proposed the Bellow-type DMFC that was expected stability of the fuel supply and its cost reduction. However, the bellows type DMFC has the problem that the output power of the cell outside area is about four times smaller than that of the cell inside area. In the previous report, the dependence of the air flow rate, the cell output power on the air supply rate when two or more cells were connected has been examined by the simulation. In addition, the air flow path has been analyzed. In this paper, a new half-cell simulation model was developed for bellows-type DMFCs and it was used to investigate the dependence of the power generation characteristics of bellows-type DMFC on the air supply.
Corrosion of Metals in Biofuels
Authors: Papavinasam Sankara , Anand Anisha , Paramesh Meenakshi , Krausher Jennifer , Li Jian , Liu Pei , Mani Saratha , Krishnamurthy Shyamala
Published: March 2011

Global annual production of bioethanol exceeds 36,500 million liters and that of biodiesel exceeds 3,524 million liters. During production, transportation and usage, biofuels come in contact with various materials (metals and non-metals). Therefore it is important to understand the influence of biofuels on materials as well as the influence of materials on biofuels. This paper summarizes our current understanding of the corrosion of metals in biofuels. The sources of biofuels have been reviewed. Different types of corrosion experienced in biofuels have been discussed. Techniques to investigate the corrosivity of biofuels have been analyzed. Future developments in this field have been highlighted.
Role of Oxygen in Localized Corrosion and Stress Corrosion Cracking of Carbon Steel in Fuel Grade Ethanol
Authors: Gui Feng , Sridhar Narasi , Beavers John
Published: March 2011

Stress corrosion cracking (SCC) of carbon steel has been observed in fuel grade ethanol (FGE). Electrochemical behavior of carbon steel and thus the role of localized corrosion in SCC has not been adequately studied due to the difficulty of performing electrochemical experiments in resistive environments such as FGE. A microelectrode technique was used in this work to conduct electrochemical studies in simulated FGE (SFGE). It was found that oxygen likely played multiple roles: it participated in the passive film formation in addition to its more commonly observed role in aqueous environments of changing the open circuit potential (OCP). A model, based on this dual role of oxygen, was proposed to explain the SCC mechanism of carbon steel in SFGE.
The Limitations of Wagner's Equation in Solid-State Electrochemistry
Authors: Miyashita Tomofumi
Published: March 2011

Numerous approaches have been proposed to describe the current-voltage relation in mixed ionic electronic solid conductors (MIEC) in a solid-oxide fuel cell (SOFC). Classically, the open-circuit voltage (OCV) is calculated with Wagner's equation. However, experimental verification of leakage currents in SOFCs using Sm-doped ceria electrolytes (SDC) is required. A simple method for the identification of leakage currents in Sm-doped ceria electrolytes in SOFCs using Wagner's equation is introduced. Furthermore, the theoretical limitations of Wagner's equation are explained. The electric field near the cathode from Wagner's equation is large enough to cause dielectric breakdown, which has never been reported experimentally. There are limitations in Wagner's equation that arise from the limits of linear transport theory.
Macroporous Ruthenium Oxide Electrodes for Electrochemical Applications
Authors: Lenz Jennifer , Trieu Vinh , Kuhn Alexander , Hempelmann Rolf
Published: March 2011

In the present work, macroporous ruthenium oxide electrodes are prepared using two template techniques, on the one hand the Langmuir-Blodgett (LB) technique and on the other hand the controlled evaporation (CE) method. In both cases, electrochemical deposition of ruthenium and ruthenium oxide is carried out on polystyrene endo-templates. With the Langmuir-Blodgett technique the number of polystyrene layers can be controlled, and with the CE method a highly networked porous structure is obtained. The CE method and the LB approach provide techniques for producing very high porosities on electrode surfaces. The large surface area due to this porous structure leads to good electrocatalytic activity. The porous ruthenium oxide was tested for pH sensing and for activation of direct NADH oxidation. Furthermore, the porous electrode was miniaturized to microelectrodes.
Evaluation of the Rate Determining Processes for LiFePO4 as Cathode Material in Lithium-Ion-Batteries
Authors: Illig Jörg , Chrobak Thorsten , Klotz Dino , Ivers-Tiffée Ellen
Published: March 2011

Lithium iron phosphate is a promising cathode material for the use in lithium-ion batteries meeting the demands of good stability during cycling and safe operation due to reduced risk of thermal runaway. However, slow solid state diffusion and poor electrical conductivity reduce power capability. For further improvement, all rate determining electrode processes have to be quantified. Electrochemical impedance spectroscopy (EIS) has proven to be a powerful tool for the characterization of electrochemical systems. In a recent publication (1), a physical interpretation for the impedance response of LiFePO4/Li-cells was given and an equivalent circuit model was proposed. In this contribution, the proposed equivalent circuit is used to quantify the predominant electrode processes depending on temperature (0°C...30°C), SoC (10% ... 100%) and microstructure characteristics (porosity).
On the High Rate Capability of LiFePO4
Authors: Boovaragavan Vijayasekaran , Srinivasan Venkat
Published: March 2011

A pseudo two-dimensional macro-homogeneous model has been used to understand the high-rate capability of LiFePO4. The circumstances that can facilitate the fast and ultra-fast rate behavior of this material are identified and discussed in detail. For the electrode designs used in the studies, it was found that the solid-phase mass transport rate has a significant effect on the rate capability of LiFePO4. The size distribution of the LiFePO4 particles has an effect on the high rate charge and discharge behavior of the material. These and other consequences are discussed using experimental data and model predictions.
Evaluation of Positive Electrode Resistance by "Current-Rest-Method" Using "Four-Electrode Cell" (Co-, Ni- and Mn-Based CathodeMaterials)
Authors: Yata Shizukuni , Satake Hisashi , Endo Tomoki , Kuriyama Mayumi , Kinoshita Hajime
Published: March 2011

In this study, we investigated the results based on the "C.R.M. ("Current-Rest-Method") resistance" of positive electrodes (Co-, Ni- and Mn-based cathode materials), which was directly related to the input-output power characteristics, using the "four-electrode cell" (1, 2, 4). By comparing the resistance of these positive electrodes, we found that the Ni-based electrode had the lowest C.R.M. resistance in the range of 4.0 V - 3.5 V and the Mn-based electrode had a stationary C.R.M. resistance over a wide range of both the charge and discharge states. In addition, the calculated curves of the Mn-based electrode revealed the excellent output power characteristics at each SOC by using the time dependence of the "C.R.M. resistance".
Improvement of Electrochemical Properties of a High Potential Negative Electrode TiO2(B)
Authors: Takagi Mikihiro , Murota Yosuke , Tajima Makoto , Asao Takayuki , Saito Morihiro , Tasaka Akimasa , Inaba Minoru
Published: March 2011

To improve the practical capacity of TiO2(B), optimization of precursor (K2Ti4O9 and Cs2Ti5O11), solvent (EC+DEC, EC+DMC and EC+DMC) in electrolyte and homogeneity (mixing with a mortar or wet-ball milling machine) of Ketjen Black (KB) as conductive agent was conducted. Use of Cs2Ti5O11 precursor reduced the content of TiO2 anatase as an impurity in the obtained TiO2(B). Choice of DMC solvent with the highest dielectric constant (3.1) and the lowest viscosity (0.59 cP) and improvement of the homogeneity of KB conductive agent enhanced the Li+ ion and electron conductivities in the electrode. As a result, the optimized TiO2(B) electrode exhibited a high discharge capacity of 314.4 mAh g-1 in 1 M LiPF6/EC+DMC(1:2), which corresponds to ca. 93.9% of the theoretical capacity of TiO2(B), 335 mAh g-1. Moreover, a high rate capability of 118.5 mAh g-1 even at 10 C was also achieved.
P-Doped Fullerene Films as Coating Materials for Silicon Film Anodes of Lithium Secondary Batteries
Authors: Arie Arenst Andreas , Lee Joong Kee
Published: March 2011

Phosphorus doped fullerene C60 (P:C60) thin films were introduced as coating materials for silicon film anodes of lithium secondary batteries using a plasma assisted thermal evaporation technique. The P:C60 coated silicon films were then used as anode materials of lithium secondary batteries. The electrochemical characteristics of the coated electrodes were studied by charge-discharge tests, cyclic voltammetry and impedance spectroscopy. Electrochemical measurements revealed that the higher coulombic efficiency of 91% and lower irreversible capacity of 298 mAhg-1on the first cycle were observed for the P:C60 coated silicon electrodes in comparison with the bare silicon case. In addition, the stable cyclic property and high capacity retention after the 30th cycle were demonstrated. All above mentioned results were attributed to the improved conductivity due to the presence of C60 coating layer which might contribute to the faster transfer of Li-ions at the electrode/electrolyte interface.
Investigations on Silicon Composite Electrodes for Lithium-Ion Batteries
Authors: Boovaragavan Vijayasekaran , Srinivasan Venkat
Published: March 2011

A porous electrode model for silicon anodes was developed and used to understand its performance. The model includes the volume change in Si and the phase transformation during the first intercalation reaction in addition to the porous electrode effect, kinetic behavior of Li+ intercalation/de-intercalation in Si, thermodynamic relationships, and mass and charge transport of Li+ in solid and liquid phases. First, the simulations were performed on a very thin (10 μm) and highly porous (80%) electrode in order to estimate the solid-phase diffusion coefficient of Li+ ions in to the Si nanoparticles. This model and experiment based investigation predicts the value of Li+ diffusion in Si to be as low as 3.25x10-16 cm2/s. Good agreement was seen between the model predictions and experimental data. The effect of particle size on the performance of Si electrode and the conditions under which Li15Si4 formation occurs during intercalation are analyzed. Next, the model was used to analyze the performance of Si when the electrode capacity is matched to a NCA cathode of 80 µm thickness and 35% porosity with a loading of 3.6 mAh/cm2 loading. The matching of the anode to cathode was performed for various cycling capacities for the Si (1000, 2000, and 3000 mAh/g) and simulations were conducted to understand the effect of rate on the charging of the anode and the associated concentration and design effects.
Comparison of Cycling Performance of Lithium Ion Cell Anode Graphites
Authors: Zheng Honghe , Ridgway Paul , Song Xiangyun , Xun Shidi , Chong Jin , Liu Gao , Battaglia Vincent
Published: March 2011

Battery grade graphite products from major suppliers to the battery industry were evaluated in 2325 coin cells with lithium counter electrodes. First and ongoing cycle efficiency, total and reversible capacity, cycle life and discharge rate performance were measured to compare these anode materials. We then ranked the graphites using a formula which incorporates these performance measures to estimate the cost of the overall system, relative to the cost of a system using MCMB. This analysis indicates that replacing MCMB with CCP-G8 (Conoco Phillips) would add little to no cost, whereas each of the other graphites would lead to a more costly system. Therefore we chose CCP-G8 as the new baseline graphite for the BATT program.
Reactivity of Nano-LaPO4 Composites in Lithium Cells
Authors: Arroyo-de Dompablo M. Elena , Amador Ulises , Lozano Esther , Baehtz Carsten , Morán Emilio , Fernandez Fuentes Antonio
Published: March 2011

Electrodes consisting of composites of nanosized-LaPO4/Carbon-Super P yield irreversible capacities as large as 872 mAh/g carbon (down to 0.2 V), which would be equivalent to the reaction of 0.9 lithium ions with LaPO4. Increasing the crystallite size of LaPO4 drastically decreases the specific capacity delivered by the cell, reaching a minimum value of 330 mAh/g carbon for micrometer-LaPO4. A significant capacity is also detected in nanosized LaPO4 /Carbon-KS6 and LaPO4/Ni electrodes. An in situ XRD investigation proves that the bulk of LaPO4 does not react with lithium, evidencing that LaPO4 is useless as electrode material for lithium cells. The reactivity of the electrode is likely due to the electrolyte decomposition on the surface of both the electronic conductor additives (C or Ni) and the LaPO4 nanoparticles.
Evaluation of Li-Metal Electrode Resistance by "Current-Rest-Method" Using "Four-Electrode Cell"
Authors: Yata Shizukuni , Mori Shiro , Satake Hisashi , Kuriyama Mayumi , Kinoshita Hajime
Published: March 2011

In the field of lithium-ion batteries, Li-metal is commonly used as the counter electrode for electrochemical measurements without regard to the resistance of the Li-metal electrodes. In this study, we focused on the Li-metal electrode resistance (the L.E. resistance) and evaluated it by the "Current-Rest-Method" using the "four-electrode cell" (1, 2). We found that the L.E. resistance during the 1st elution process is significantly higher than the resistance of the commonly-used negative electrodes. Moreover, the L.E. resistance remarkably varied with changes in the geometry of the L.E.
Thin Film Copper Vanadium Oxide Electrodes for Thermal Batteries
Authors: Dai Jinxiang , Lai Monique , LaFollette Rodney M. , Reisner David
Published: March 2011

In this work, thin film copper vanadium oxide electrodes including Cu3V2O8 and Cu5V2O10 were prepared by an aqueous process for thermal batteries. The electrochemical performances of thin film electrodes were tested and evaluated in thermal cells. Comparing with pressed pellet electrodes, the thin film electrodes were able to deliver higher specific capacities. Without any organic solvent and binder, the process for making the film electrodes is low cost and environmental benign.
Electrochemical Synthesis of Oxygen Reduction Catalysts Based on Pt Coated Polypyrrole Nanowires Using Starch as Template Molecule
Authors: Sansiñena José-María , Nelson Mark , Wilson Mahlon S. , Garzón Fernando H.
Published: March 2011

This study demonstrates a new method for the development of low loading Pt catalysts for the oxygen reduction reaction (ORR) based on the electrochemical synthesis of Pt coated polypyrrole (PPY) nanowires. PPY was deposited on different electrodes such as graphite, carbon paper gas diffusion layer (GDL), and glassy carbon by using chemical template molecules such as heparin and starch. Pt coated PPY/starch nanowires show ORR catalytic activity after the electrochemical degradation of PPY, which suggests that PPY/starch nanowires can be electrochemically converted to a stable high surface area support for ORR catalysts. Moreover, these low loading ORR Pt catalysts can be easily incorporated in the membrane electrode assembly (MEA) structure as a gas diffusion electrode (GDE) when directly prepared on a GDL.
A New Synthetic Route of LiFePO4 Nanoparticles from Molten Ingot
Authors: Zaghib Karim , Charest Patrick , Dontigny Martin , Labrecque Jean-Francois , Mauger Alain , Julien Christian M.
Published: March 2011

LiFePO4 (LFP) nano-particles have been obtained by grinding ingot synthesized in the molten state. This process, followed by jet milling, and then wet milling, provides a simple way to obtain powders with monitored size of the particles in the whole range from macroscopic to 25 nm, although at this stage, we find that these particles tend to segregate to form secondary particles of size ~100 nm. The electrochemical performance of LFP particles has been evaluated in Li/1M LiPF6 in EC:DEC (1:1)/C-LiFePO4 cells. After carbon coating, LFP particles can be obtained free from any impurity, with a high rate capability. Even with an amount of carbon limited to 2 wt.% appropriate to commercial batteries, the capacity is 157 mAh/g at 0.1C; 58 mAh/g at 10C without capacity fading after 60 cycles.
Tuning Silicon Nanorods for Anodes of Li-Ion Rechargeable Batteries
Authors: Au Ming , Garcia-Diaz Brenda , Adams Thad , He Yuping , Zhao Yiping , Yassar Reza Shahbazian , Ghassemi Hessam
Published: March 2011

Silicon is a promising anode material for Li-ion batteries in regarding of high capacity, low cost and safety, but it suffers poor cycling stability due to the pulverization induced by severe volume expansion/shrinkage (297%) during lithium insertion/extraction. In our previous investigation on aluminum nanorods anodes, it is found the selection of substrates in which Al nanorods grown plays the significant role in prevention of pulverization resulting in the increase of cycling life [1]. Adapting this knowledge, we investigated the Si based nanorods by tuning its composition and element distribution. Our results show that the Si-Cu composite nanorods demonstrated sustainable capacity of 500 mAh/g in 100 cycles attributing to its flexible and less brittle nature.
Improve the Efficiency of Silicon Solar Cells by ITO-Silver Electrode Structure
Authors: Jehng Wern-Dare , Chen Chih Wei
Published: March 2011

In this study, Indium Tin Oxide thin film composite nano silver film was used to replace the positive silver gate-like electrodes commonly use by silicon solar cells. The study aimed to increasing the area of light absorption for silicon solar cells thereby enhance the solar cell optoelectronic conversion efficiency. The experiment adopted sol-gel solution containing phosphorus which was used as the source of phosphorus dopant. The solution was spin-coated on single crystal silicon, followed by high temperature annealing to form p-n junction. This substrate was coated with nano silver film of different thicknesses, while the coating of Indium Tin Oxide with thickness of 450nm was used as the front electrode, to increase solar cell efficiency. The study proposed an appropriate thickness of nano silver film which could effectively improve the diode properties of components and provide better efficiency for solar cells with such structure.
Anodic Dissolution Behavior of Magnesium in Hydrophobic Ionic Liquids
Authors: Sasaki Izuru , Murase Kuniaki , Ichii Takashi , Uchimoto Yoshiharu , Sugimura Hiroyuki
Published: March 2011

Anodic dissolution behavior of magnesium (Mg) metal was examined in an ionic liquid bath containing Mg(II) ions as Mg(Tf2N)2. A set of sampled-current voltammograms obtained by a potential-step method revealed that the Mg2+/Mg0 redox potential in the ionic liquid was +1.41 V vs. Li+/Li0, and was little affected by residual water in the ionic liquid. It was found, in contrast, that the residual water increased faradaic current density for the anodic dissolution of Mg and also the apparent exchange current density of the Mg2+/Mg0 redox.
Effect of Electrolyte on the Electrochemical Reduction of CO2
Authors: Salazar-Villalpando Maria D.
Published: March 2011

Electrochemical experiments were carried out in a laboratory-made, divided H-type cell to study the electrochemical reduction of CO2. A copper wire, Ag/AgCl electrode and Pt wire were used as the working, reference and counter electrode, respectively. A potential ramp between 0 and -1.2 V was applied to the cell and the current was monitored as a function of potential. The effect of the electrolyte on the electrochemical reduction of CO2 was investigated by using NaHCO3 and KHCO3. It was observed that the latter electrolyte favored higher currents. This may be related to the cation size and electro negativity. The role of the electrolyte in this reaction may be explained by assuming that CO2 bonds to HCO3- and K+, generating intermediate specie prior to its electrochemical reduction. This would explain that the current increased as a function of KHCO3 concentration. The insertion of CO2 between the anion and the cation is a very important step in the electrochemical reaction. The formation of a new HCO3-C bond results in the weaking of C-O bond and the activation of CO2 occurs. The electron transfer from the electrode to the CO2 is facilitated.
Preparation and Study of Proton Composite Electrolyte CsHSO4/SiO2 with Different Architecture
Authors: Lavrova Galina , Ponomareva Valentina , Zyryanov Vladimir V.
Published: March 2011

This work is directed on the optimization of composite electrolytes microstructure and synthesis of dense composite electrolytes with the more homogeneous salt distribution in the matrix with nanosize pores. The method of the milling of the components with following separation of the fine fraction (<10μm) in Electro-mass-classifier technique was used for these purpose. The method is promising for the preparation of solid electrolytes with optimal transport and mechanical properties related to adjusted architecture.
Ultracapacitor Performance of Reduced Graphene Oxide - Silica Composite
Authors: Murali Shanthi , Stoller Meryl , Morales Cornelio , Velamakanni Aruna , Zhu Yanwu , Ruoff Rodney
Published: March 2011

Graphene's unique properties show great promise for ultracapacitor applications. However, increasing the surface area available to electrolyte to increase the specific capacitance remains a challenge. In this paper we report on a method to synthesize a reduced graphene oxide-silica nanoparticle composite followed by etching with hydrofluoric acid. The composite and the etched samples were characterized using scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Nitrogen adsorption and capacitance measurements indicated an increase in the specific surface area and the specific capacitance in the post-etched samples suggesting that the silica nanoparticles act as a sacrificial jamming agent.
Electrochemical Considerations in Supercapacitors with Nanocomposites
Authors: Peng Chuang , Zhou Xiaohang , Zhang Shengwen , Chen George
Published: March 2011

This paper presents an account of some electrochemical aspects in relation to supercapacitors (SPs) with composite electrodes of carbon nanotubes and redox pseudocapacitive materials. Firstly, the origin of pseudocapacitive behaviour is rationalised by the band theory of solids. The maximum achievable mass specific capacitance of conducting polymers is also considered by calculations with the aid of a new ferrocenyl bithiophenic polymer capable of both capacitive and non-capacitive faradaic charge transfer reactions. Another aspect considered is the relationship of the ratio of positive and negative electrode capacitances with the voltage and energy capacity of asymmetrical SPs. This work has led to significantly increased energy storage capacity. A novel trenched graphite disc electrode and a tube-type two electrode cell for SP fabrication are also introduced in this paper. Lastly, the fabrication and performance of a 20 V SP stack is reported.
Flexible Carbon Nanotube and Paper Electrochemical Double Layer Capacitors Using PVA-KOH Gel Electrolytes
Authors: Anton Christopher M. , Ervin Matthew H.
Published: March 2011

Electrochemical double layer capacitors are fabricated using CNT/paper flexible electrodes. An extensive electrode fabrication study was conducted, resulting in single electrode specific capacitances in excess of 100 F/g. Surfactants and dispersants in the CNT suspension prior to CNT deposition onto paper substrates were found to be detrimental to electrode performance. Following electrode fabrication, three full cell packaged supercapacitor architectures were investigated. One architecture utilized a liquid KOH electrolyte, while the other two architectures used a PVA:KOH gel electrolyte. Devices were tested under static bending conditions, and proved to function under bending.
Optimized Cu Contacted Si Nanowire Anodes for Li-Ion Batteries Made in a Production Near Process
Authors: Föll Helmut , Carstensen Juergen , Ossei-Wusu Emmanuel , Cojocaru Ala , Quiroga-González Enrique , Neumann Gerold
Published: March 2011

Anodically etching macropores in Si substrates followed by chemical over-etching and Cu galvanics allows producing Si nanowire anodes for Li ion batteries with optimized geometry. First tests of these electrodes in batteries yielded very good results with respect to capacity, cycle stability, and irreversible Li losses. This paper focuses on the optimizations of the process chain. Processing times for key process could be substantially reduced while concomitantly improving the quality and the process window. Problems like Li leakage into the Si substrate have been eliminated. The process chain now is close to enabling mass production on 200 mm wafers.
Electrode Properties of Nanosheet-Derived MnO2 for Electrochemical Capacitors
Authors: Jang Hwamyung , Suzuki Shinya , Miyayama Masaru
Published: March 2011

Layer-structured MnO2 electrodes were synthesized by using a nanosheet process and its electrode properties for electrochemical capacitors were investigated in aqueous solutions. Prepared MnO2 nanosheet had a plate like morphology, 3 µm in width and 3 nm in thickness. In an aqueous 0.1 M Na2SO4 solution, the nanosheet-derived MnO2 electrode (K-NS) showed a good cyclic performance and exhibited a discharge capacity of 168 F/g-MnO2 at a current density of 50 mA/g-MnO2. In an aqueous 0.1 M KOH solution, however, K-NS showed a large irreversible capacity and exhibited a discharge capacity of 133 F/g-MnO2 at the second cycle. The large irreversible capacity of K-NS was cause by the generation of Mn3O4 phase which is an electrochemically inactive phase.
Sulfonated Polystyrene-Block-(Ethylene-Ran-Butylene)-Block-Polystyrene (SPSEBS) Membrane for Sea Water Electrolysis to Generate Hydrogen
Authors: Ravichandran Subbiah , Balaji Rengarajan , Kannan Balasingam Suresh , Elamathi Swaminathan , Sangeetha Dharmalingam , Lakshmi Jothinathan , Vasudevan Subramanian , Sozhan Ganapathy
Published: March 2011

Sea water oxidation is one of the promising ways to produce hydrogen since it is available in plentiful supply on the earth. However, in sea water electrolysis poisonous chlorine evolution is the most favored reaction over oxygen evolution at the anode. In this work, study has been focused on the development of electrode materials with high selectivity for oxygen evolution reaction over chlorine evolution. We employed perm selective membrane i.e. sulfonated polystyrene-block-(ethylene-ran-butylene)-block-polystyrene (SPSEBS) which electrostaticlly repels the chloride ion (Cl-) to the electrode surface and thereby enhances the oxygen evolution and reduces the chlorine evolution at the anode. The electrochemical behavior of both modified and bare IrO2 electrodes were characterized using polarization studies and the gas evolution efficiencies are calculated based on bulk electrolysis method. The surface morphology of the electrode was analyzed before and after electrolysis using scanning electron microscope (SEM). The results suggest that the nearly 95% oxygen evolution efficiency could be achieved when the surface of IrO2/Ti electrode was modified with perm selective membrane.
Development of Non-Pt Electrocatalysts towards Hydrogen Evolution Reaction for Gas-Phase Br2-H2 Flow Battery
Authors: Zhang Rui , Stanford Thomas G. , Wolters Laura , Weidner John
Published: March 2011

A gas-phase HBr/Br2 flow battery is setup. The equilibrium cell potential of the flow battery is calculated by Nernst equation incorporated with Br2-HBr-H2O phase equilibrium in Aspen OLI lab. The calculated equilibrium cell potential is compared with the experimental open circuit voltage. Polarization of this flow battery is investigated at both electrolzyer and fuel cell modes with respect to different content of bromine. Because of the poisoning effect of bromine and bromide ions on Pt, non Pt electrode materials need to be developed. For the hydrogen evolution reaction (HER), activities of MoS2 and IrO2/C are tested on the rotating disk electrode with cyclic voltammetry and psedosteady state polarization. XRD and HRTEM are used to characterize the morphology and structure.