bluuebunny/crossref_metadata_2025 huggingface dataset:
A Multiple Magnetoelastic Sensor System for Detection of Salmonella Typhimurium Using Pulse Method
Authors: Shen Wen , Li Suiqiong , Horikawa Shin , Chin Bryan
Published: October 2010

Magnetoelastic sensors show a resonance frequency decrease once target pathogens are attached to the sensors and thus add a small mass to the sensors. These sensors are fast, sensitive, and have higher mass sensitivity with smaller sized sensors. However, signals from smaller sensors are weaker and have more noise due to manufacturing defects. In this paper, we present a pulse biosensor system that is able to avoid bias magnetic field and allows simultaneous detection using multiple sensors. With multi-sensors, the effect of a manufacturing defect is decreased and we get the benefit of averaging for more accurate and reliable results. Stability tests show that the variance of frequency detection is less than 122 ppm of its resonance frequency. Real detection of pathogen is demonstrated using Salmonella typhimurium and the results show that multiple magnetoelastic biosensors are able to detect S. typhimurium simultaneously and offer good sensitivity and reliability.
Metal Hexacyanoferrate with Conducting Polymer Composite Film Modification Electrodes for Selectively Determination of AA, DA and UA
Authors: Chen Tse-Wei , Tsai Tsung-Hsuan , Chen Shen-Ming
Published: October 2010

This present work describes oxidation of ascorbic acid (AA) at poly(3,4-ethylenedioxy-thiophene) (PEDOT)/nickel hexacyano-ferrate (NiHCF), PEDOT/copper hexacyanoferrate (CuHCF) and manganese hexacyanoferrate (MnHCF) film were modified on glassy carbon electrode (GCE). The NiHCF-PEDOT, CuHCF-PEDOT and MnHCF-PEDOT hybrid materials are characterized using scanning electron microscope (SEM) techniques. The advantages of these films are demonstrated for selectivity detection of ascorbic acid using cyclic voltammetry and amperometric method. Interestingly, the PEDOT-NiHCF and PEDOT-CuHCF modified electrode exhibited a wide linear response range (from 5 x 10-6~3 x 10-4 M, R2 = 0.9973 and 1.8 x 10-3~1.8 x 10-2 M, R2 = 0.9924). The electrochemical sensors facilitated the oxidation of AA but not responded to other electroactive biomolecules such as dopamine, uric acid, H2O2, glucose. The difference is MnHCF-PEDOT/GCE that no response to AA. In addition, the NiHCF-PEDOT and CuHCF-PEDOT modified electrodes exhibited a distinct advantage of simple preparation, specificity, stability and reproducibility.
Gas Sensing Properties of Co3O4-Doped Bismuth Oxychloride Nanowires and Nanoribbons
Authors: Michel Carlos R. , Cruz-Hernández Alejandra , Yocupicio Angel
Published: October 2010

Co3O4-doped bismuth oxychloride (BiOCl) nanowires and nanoribbons were prepared by a surfactant-assisted method. Bismuth trichloride, cobalt nitrate and polyvinyl pyrrolidone were used as reagents. The calcination of the precursor material at 600ºC produced a Co3O4-BiOCl composite, which was characterized by X-ray powder diffraction. Nanowires and nanoribbons were identified by scanning and transmission electron microscopies. The length of them was in the range of 50 to 600 micrometers, with a cross section size between 50 nm and 15 micrometers. Thick-films of the as-prepared powders were tested as CO2 gas sensors. The Co3O4-BiOCl composite sensor device behaves as a p-type semiconductor material, having variations of |Z| of ~2.2 Mohms,at 200ºC. A uniform and reproducible CO2 gas response pattern was obtained, suggesting this material as an alternative gas sensor.
pH Micro-Sensors Associated with Micro-Fluidics for Chemical Analysis
Authors: Kherrat Abdelghani , Le Bihan France , Razan Florence , Coulon Nathalie , Griscom Laurent , De Sagazan Olivier , Crand Samuel , Mohammed-Brahim Tayeb
Published: October 2010

For water monitoring or many chemical or biological applications, pH measurements are very important, and especially the detection of a small pH changes. Such applications require the development of microsystems that present high sensitivity to pH, have a simple use, a low cost and a small size. This present pH sensor is a highly sensitive Suspended Gate Field Effect Transistors (SGFET) interfaced with PDMS microfluidic channels. This microsystem allows the transport and the testing of the liquid. The compatibility of the two technologies is checked by controlling and optimizing the sticking between PDMS and the surface of the sensor, the good electrical insulation, the control of the sensor electrical behavior after sticking. Preliminary tests have validated the possibility of detecting the presence of liquids flowing through microchannels. These micro-chambers can be used for specific biological phenomena inducing these changes in pH (enzymes, cells).
Fabrication of Silicon Needle-Like Structures Suitable for Controlled Gas Permeability
Authors: Sanaee Zeinab , Mohajerzadeh Shams
Published: October 2010

The fabrication of hollow silicon microneedles on silicon membranes is reported. Using high-resolution vertical etching and small angle deposition of a chromium layer allows fabrication of hollow structures without a need to 3D lithography or extra mask alignment. Silicon microneedles with inner diameters of 0.5-3μm and a wall thickness of 100-300nm are realized using hydrogen-assisted deep reactive ion etching (DRIE). Growing carbon nano tubes on top of this structure leads to a cage-like structure, which could have the ability of controlling gas transport across the tiny holes. CNTs serve as the surrounding "bars" for this cage-like structure.
Novel Photolithography Yield-Enhancement Technique: Megasonic-Enhanced Development
Authors: Dragoi Viorel , Bartel Johanna , Dussault Don
Published: October 2010

MEMS-specific processes required to adapt standard IC manufacturing technologies in order to accommodate its custom requirements. Photolithography is one of the standard techniques which had to adapt particularly to the use of thick resists needed for high aspect ratio features fabrication. In order to work with resist thickness varying between few tens and up to few hundreds of micrometers the standard process flow had to be changed to multiple-layers coating, customized (and very long) baking times, special exposure techniques and development. This paper introduces a megasonic-enhanced method used for developing resists. In case of MEMS applications this method brings not only a major yield improvement (better quality features) but also a major decrease of process time.
Characterization of HKUST-1 Crystals and Their Application to MEMS Microcantilever Array Sensors
Authors: Venkatasubramanian Anandram , Lee Jin-Hwan , Houk Ronald J. , Allendorf Mark D. , Nair Sankar , Hesketh Peter J.
Published: October 2010

In this paper, thermodynamic characterization of the well known MOF HKUST-1 has been conducted using Quartz Crystal Microbalance (QCM) with the analyte gas CO2 for a wide range of temperatures and pressures. The thermal characterization of HKUST-1 was performed by measuring the shift in resonant frequency of the crystal, to calculate the adsorption isotherms. The adsorption isotherms were then fit to Langmuir isotherms to obtain the thermodynamic parameters. HKUST-1 was then successfully applied to microcantilever for sensor application. N-doped piezoresistive microcantilever array sensors were fabricated using microfabrication technologies. The substantial resistance changes with MOFs exhibited a strong and completely reversible response for adsorption and desorption.
Novel Concept for the Formation of Sensitive, Selective, Rapidly Responding Conductometric Sensors
Authors: Gole James L. , Ozdemir Serdar , Osburn Thomas B.
Published: October 2010

Rapidly responding, reversible, sensitive, and selective porous silicon-based gas sensors, operating at room temperature, are formed with a highly efficient electrical contact to a nanopore covered microporous array. Variable surface sensitivities are facilitated for a variety of gases, based on a complementary concept to that of strong and weak acid-base (HSAB) interactions and commensurate with a basis in physisorption. A range of highly selective surface coatings has been created. A "Materials Selection Table", implemented on 'phase matched' silicon nanopores positioned on porous silicon micropores facilitates the application of nanostructured metals, metal oxides, and nanoparticle catalytic coatings, providing for notably higher sensitivities and selectivity. Single nanostructure depositions, which include electroless gold, tin, copper, and nickel, as well as nano-alumina, magnesia, and titania provide for the detection of gases including NO, NO2, CO, NH3, PH3, SO2, H2S, HCl, and toluene in an array-based format at the sub-ppm level.
An Ultra-Low Power Microbridge Gas Sensor
Authors: Aguilar Ricardo , Peng Zhengchun , Hesketh Peter J. , Stetter Joseph
Published: October 2010

A miniature, ultra-low power, sensitive, microbridge-based thermal conductivity gas sensor has been developed. The batch fabrication of the sensors was realized by CMOS compatible processes and surface micromachining techniques. Doped polysilicon was used as the structural material of the bridge with critical dimension of 1µm. The sensor has been tested with nitrogen, carbon dioxide, and helium. Heat loss from constant voltage application was observed to be a function of the thermal conductivity of the gas ambient, resulting in different magnitude of resistance change. The response time to a voltage pulse was found to be less than 0.5µs and stability of the sensor excellent. We demonstrated that the sensitivity for helium in nitrogen was 2.05mΩ/ppm when operated at 3.6V dc supplies (a power level in the order of 4 milliwatts). With a Wheatstone bridge with ac excitation and a Lock-in amplifier the sensor limit of detection was ~100ppm helium in nitrogen.
Development of High Temperature Wireless Sensor Technology Based on Silicon Carbide Electronics
Authors: Hunter G. , Beheim Glenn , Ponchak George , Scardelleti Maximillan , Meredith Roger , Dynys Fred , Neudeck Philip , Jordan Jennifer , Chen Liang-Yu
Published: October 2010

Smart Sensor Systems that can operate at high temperatures are required for a range of aerospace applications including propulsions systems. This paper discusses the development of a high temperature wireless system that includes a sensor, electronics, wireless communication, and power. In particular, a wireless pressure sensor was demonstrated at 300°C, with signal transmission over one meter distance and power derived from scavenged energy. The circuit had a nominal oscillation frequency of near 100 MHz and used a commercial SiC metal semiconductor field effect transistor (MESFET) together with metal-insulator-metal (MIM) capacitors and a thin film inductor/antenna. With the sensor and oscillator circuit at temperatures from 25 to 300°C, the oscillator frequency, detected at a distance of one meter, was found to vary repeatably as a function of pressure. This work is considered a foundation for the development of higher temperature Smart Sensor Systems for use in harsh environments.
(Invited) The Development and Fabrication of MEMS in the Semiconductor World
Authors: Winterton Gregory
Published: October 2010

The Texas Instruments Digital Micromirror Device (DMD) microelectomechanical system (MEMS) has been developed over several generations along side the traditional semiconductor manufacturing line using the same toolset and manufacturing infrastructure as standard CMOS processing in the DMOS5 wafer fab. This unique arrangement has allowed Texas Instruments to leverage years of experience in semiconductor manufacturing in the development and manufacture of this MEMS device. The co-location of MEMS develpment in the semiconductor line allows the use of existing semiconductor infrastructure to aid the development and eliminates the need of transition to a manufacturing facility. This approach also allows Texas Instruments to re-task older existing toolsets to MEMS manufacturing further enhancing their productive lifetime.
Self Patterned Gold Electroplating for High-Aspect-Ratio MEMS Structures
Authors: Zareie Hosein , Agah Masoud
Published: October 2010

This paper reports on a method for self-patterned pulse electroplating to selectively deposit gold on vertical surfaces of microfabricated silicon channels with a width of 30µm, a height of 250µm and spacing of 30µm. The electric field was simulated inside the channels. The results show that gold could be deposited only on vertical sidewalls of these structures.
PEM Fuel Cell Degradation
Authors: Borup Rodney L. , Mukundan Rangachary
Published: October 2010

The durability of PEM fuel cells is a major barrier to the commercialization of these systems for stationary and transportation power applications. While significant progress has been made in understanding degradation mechanisms and improving materials, further improvements in durability are required to meet commercialization targets. Catalyst and electrode durability remains a primary degradation mode, with much work reported on understanding how the catalyst and electrode structure degrades. Accelerated Stress Tests (ASTs) are used to rapidly evaluate component degradation, however the results are sometimes easy, and other times difficult to correlate. Tests that were developed to accelerate degradation of single components are shown to also affect other component's degradation modes. Non-ideal examples of this include ASTs examining catalyst degradation performances losses due to catalyst degradation do not always well correlate with catalyst surface area and also lead to losses in mass transport.
PEMFC Electrocatalyst Development
Authors: Stevens David , Hatchard Tim , Sanderson Robbie , Atanasoski Radoslav T. , Debe Mark K. , Dahn Jeff
Published: October 2010

Performance, cost and durability aspects of catalysts for proton exchange membrane fuel cells are discussed in the context of the US Department of Energy performance targets for automotive applications. State of the art catalysts are close to meeting the targets for these three important parameters. More work is required to further increase performance, reduce platinum loadings, and minimize the potentials the cathode catalyst can reach during adverse conditions such as those that will occur during fuel cell startup and shutdown
Mechanisms of Morphology Development and Water Motion in Proton Exchange Membranes
Authors: Hickner Michael
Published: October 2010

Two critical parameters of nanophase morphology and water motion are discussed in the design of proton exchange membranes (PEMs). While much has been learned about the function of proton exchange membranes by studying poly(perfluorosulfonic acid) and sulfonated aromatic polymers, new generations of electrolytes for aqueous applications are being developed that push the limits of ion conductivity and small molecule transport rates in water-absorbing polymers. The utility of employing block copolymers has been demonstrated to concentrate and affect long-range connectivity of ionic domains, but the details of how ions arrange in these systems are still to be explored. Examples of block copolymer proton exchange membranes and their usefulness in understanding membrane function will be reviewed. Additionally, water motion in PEMs is critical to achieving sufficient proton conductivity. The relationship between water motion and conductivity can be used to design new materials with insight of the water-polymer interactions in the system.
Nucleation of Platinum on Carbon Blacks
Authors: Berliba-Vera Elena K. , Delariva Andrew T. , Atanassov Plamen , Datye Abhaya K. , Garzón Fernando H.
Published: October 2010

One of the outstanding challenges in the wider deployment of PEMFCs is improving the utilization of Pt. While decreasing particle size improves accessibility of the Pt, it also destabilizes the Pt particles and leads to dissolution/re-precipitation and rapid grain growth. A parameter that is as yet poorly characterized is the number of nucleation sites on the carbon support. Increased nucleation site density could provide a valuable approach to improve Pt utilization. In this work, nucleation density was characterized by determining the number of particles per nm2. A range of metal loadings were explored to investigate their effect on the number of Pt particles on three types of carbon support. It was concluded that the number of nucleation sites is relatively constant over the Vulcan family of carbon supports. However, activated carbons such as Norit SX-1G show much higher nucleation density.
Pt/C Catalyst for PEMFC Synthesized by a Pulse Microwave-Assisted Solvent Chemical Reduction Process
Authors: Zheng Jun-Sheng , Wang Xi-Zhao , Fu Rong , Yang Daijun , Lv Hong , Ma Jianxin
Published: October 2010

Pt/C with a platinum content of 20 wt% was synthesized by a Pulse Microwave-assisted solvent chemical reduction (PMWSCR) process, and the as-grown nanocomposites have been applied as electrocatalyst for oxygen reduction reaction (ORR). For comparison, platinum nanoparticles based on carbon support with 40 wt% platinum are prepared by chemical reduction. High resolution transmission electron microscope (HRTEM) images show that the size of platinum nanoparticles synthesized by PMWSCR is about 1 nm, distinctly smaller than those prepared by chemical reduction. Cyclic voltammetric analysis in a nitrogen saturated electrolyte reveals that the electrochemical surface area of electrocatalyst by PMWSCR is larger than that by chemical reduction. Moreover, Pt/C synthesized by chemical reduction is less active than that prepared by PMWSCR.
Spectroscopic Identification of a Hydrogen Peroxide-Like Intermediate Formed after Molecular Oxygen Adsorption on Hydrogen Rich Pt(111)
Authors: Näslund Lars-Aåke , MacNaughton Janay , Anniyev Toyli , Ogasawara Hirohito , Nilsson Anders
Published: October 2010

Using polarization dependent O 1s x-ray absorption spectroscopy we identify a hydrogen peroxide-like intermediate on the surface of hydrogenated Pt(111) after exposure of a saturated amount of molecular oxygen. The x-ray absorption spectroscopy investigation further reveals that the O-O molecular axis of the hydrogen peroxide-like intermediate is close to parallel and the O-H group is perpendicular to the surface. The O-O bond length is determined to be 1.43 Aå.
Size-Dependent Activity of Platinum Nanoparticles for Oxygen Reduction Reaction in a PEFC with a Multiscale Approach
Authors: Makino Katsunori , Chiba Mahito , Koido Tetsuya
Published: October 2010

Quantum calculations to determine the elementary reaction rates of oxygen reduction reaction (ORR) on platinum surface, the Dynamic Monte Carlo simulation on {111} and {100} facets, and the geometrical statistics of the numbers of the atoms on the facets of platinum nanoparticles are combined to analyze the size effect of the nanoparticles for ORR in a PEFC. The mass activity (MA) is maximized at a certain sphere diameter with an equivalent volume. It depends on the shape of the nanoparticle.
Role of Particle Size Distribution on Pt Stability
Authors: Trogadas Panagiotis , Fuller Thomas F.
Published: October 2010

This work aims to address the role of particle size distribution on Pt stability. A theoretical model is built based on modified Butler-Volmer equations, platinum oxide surface coverage and interparticle interactions between platinum oxide particles. Preliminary results demonstrate the change in platinum ions concentration across the electrode and membrane and reveal the effect of potential cycling on the particle size. Further research on the effect of particle size and potential cycling on electrochemically active surface area and its comparison with experimental data is in progress.
Nanostructured Catalytic Electrodes for Low-Temperature Fuel Cells: Activation of Reactive Sites through Modification with Ultra-Thin Films of Metal Oxo Species
Authors: Kolary-Zurowska Aneta , Zurowski Artur , Marassi Roberto , Kulesza Pawel J.
Published: October 2010

We describe a new preparation method for preparation of a stable water-insoluble composite film containing platinum nanoparticles dispersed in conductive high-surface-area zeolite-type matrices of Vulcan XC-72 carbon supported acidic salts of cesium phosphododecatungstate (Cs2.5 H0.5PW12O40). To obtain the composite, Pt is obtained through corrosion of a Pt flag counter electrode (in 0.5 moldm-3 H2SO4/5 mmol dm-3 KCl using cycling voltammetry) and deposited on the working electrode (glassy carbon) substrate modified with Cs2.5H0.5PW12O40 mixed with Vulcan XC-72 carbon nanoparticles. For comparison, we also have considered the working electrode modified with Vulcan (XC-72) carbon nanoparticles. High resolution transmission electron microscopy (HRTEM) has been utilized to investigate dispersion platinum nanoparticles deposited on the polyoxometallate matrix. CO-stripping voltammetry has been used to determine the Pt surface area in the catalytic layer. The results have shown high electrocatalytic activity of the electrode containing low loading of Pt nanoparticles (about 2.6 μg cm-2 and of the size 1-2 nm) towards oxygen reduction. It is expected that Pt is located inside pores of zeolitic Cs2.5H0.5PW12O40. The electrochemical behavior of the Cs2.5H0.5PW12O40 salt has been asessed using cycling voltammetry. Reactivity of Pt-free Cs2.5H0.5PW12O40 system towards reduction of hydrogen peroxide (i. e., the undesirable oxygen reduction intermediate) has also been addressed.
Extraordinary Oxygen Reduction Activity of Pt3Ni7
Authors: Debe Mark K. , Steinbach Andrew J. , Vernstrom George D. , Hendricks Susan M. , Kurkowski Michael J. , Atanasoski Radoslav T. , Kadera Paul J. , Stevens David A. , Sanderson Robert J. , Marvel Eleizer , Dahn Jeff R.
Published: October 2010

Nanostructured thin film catalysts (NSTF) with widely varying compositions of PtxMyNz (M, N = Ni, Co, Zr, Hf, Fe, Mn) have been evaluated for 0 < x,y,z < 1. The catalysts' activity for oxygen reduction (ORR) was measured in 50 cm2 fuel cell membrane electrode assemblies. PtxNiy was found to be unique in showing an extraordinarily sharp peak in ORR activity as a function of the as-made composition around x=3, y=7. This composition gave a corresponding fcc lattice parameter of 3.71 Angstroms and a grain size of 7.5 nm. Both surface area and specific activity increases contribute to the increased mass activity. The ORR mass activity of the Pt3Ni7 is 60% higher than for the NSTF standard Pt68Co29Mn3 alloy.
Catalytic Activity of Pt1-xNix (0 < x < 0.8) Measured on High Surface Area NSTF-Coated GC Disks
Authors: Liu Gary C. , Burns Chris , Sanderson Robbie , Stevens David , Vernstrom George D. , Atanasoski Radoslav T. , Debe Mark K. , Dahn Jeff
Published: October 2010

Intermixed Pt1-xNix (0 < x < 0.8) and Pt were sputter-deposited onto high surface area, NSTF-coated GC disks and studied for oxygen reduction reaction (ORR) activity by rotating disk electrode (RDE). NSTF-coated GC disks used in RDE experiments is a viable alternative to the regular mirror-polished GC disks in screening catalyst activities because both the catalytic activities and the effects of high-surface area support can be examined in a single measurement. The sputtered Pt-Ni samples have a much higher Surface Enhancement Factor (SEF) and kinetic current density. The impact of potential cycling is also included in this work.
Electrochemical Characterization of Various Carbon-Supported Pt-Pd Bimetallic Electrocatalysts Prepared by Electroless Deposition
Authors: Ohashi Masato , Monnier John , Van Zee John W.
Published: October 2010

Various Pt-Pd/C bimetallic compositions have been prepared by electroless deposition (ED) methods. The morphology has been identified as Pd cores partially encapsulated by Pt shells by various spectroscopic techniques. No monometallic Pt or Pd particles have been detected. The ratio of Pt to Pd was also well controlled. Although the electrochemical activity of the Pt-Pd/C catalyst for oxygen reduction reaction (ORR) was equal to or less than that for commercially available Pt/C catalysts, the amount of hydrogen peroxide detected as ring current was reduced by the exposed Pd component, suggesting that such a catalyst has the potential to decrease ionomer degradation in certain applications. The Pt on Pd/C catalysts also show much higher resistance to agglomeration induced by potential cycling. Analysis by high resolution scanning transmission electron microscopy following potential cycling reveals no changes in both particle sizes and electrochemical active areas.
Microstructure-ORR Activity Relationships in Pd3M (M = Cu, Ni, Fe) Electrocatalysts Synthesized at Various Temperatures
Authors: Ramanathan Mayandi , Li Bing , Greeley Jeffrey , Prakash Jai
Published: October 2010

The oxygen binding energy (BEO), considered to be an important descriptor for ORR catalytic activity on transition metal alloys, was calculated using ab initio Density Functional theory calculations to probe the ORR activity of Pd3M/C (M = Fe,Ni,Cu) alloys. Variation in BEO with binding site were ascribed to changes in ORR activity due to varying catalytic surfaces developed at different annealing temperatures. Relative binding energies of *O and *OH predicted higher ORR activity for Pd3Cu on bulk surfaces and for Pd3Fe on Pd skin surfaces when compared to pure Pd. Pd3M/C (M = Fe,Ni,Cu) electrocatalysts were synthesized at temperatures from 300 to 800{degree sign}C and the electrochemical surfaces were characterized by Cyclic Voltammetry. Typical rotating disk currents for Pd3M alloys showed higher ORR activity for Pd3Fe/C and Pd3Cu/C annealed at higher temperatures. Koutechy-Levich Plots for Pd3Fe/C and Pd3Cu/C showed four electron transfer for oxygen reduction and better kinetic parameters than Pd.
Ammonia Oxidation Enhancement at Square-Wave Treated Platinum Particle Modified Boron-Doped Diamond Electrodes
Authors: González-González Ileana , Hernández-Lebrón Yaritza , Nicolau Eduardo , Cabrera Carlos R.
Published: October 2010

The catalytic performance of nanoparticles can be tuned either by their composition, which mediates electronic structure, or by shape. The shape of a particle is determined by the surface atomic arrangement and coordination. This is affected by the chosen route to synthesize the particle. The route we employed for treating Pt nanoparticles through the application of a square-wave potential is presented. This treatment enhanced the ammonia oxidation stability at platinum modified boron-doped diamond electrodes. Starting from Pt nanoparticles electrodeposited on diamond substrate instead of bulk Pt, we obtained tetrahexahedral Pt nanoparticles. SEM images showed platinum particles with an irregular shape, close to it several regular sharp shaped platinum particles with a size regime of tenths (100-10 nm) of nanometers. Skeleton type particles appear to be the remains of the precursor platinum particles after the square wave treatment breaks down the platinum particles. Platinum features were not shown on the cyclic voltammograms for treatments longer than 30 minutes. This treatment debilitates the C-O-Pt interaction that provides the stability of the platinum particles on the diamond (111) surface. Non-treated particles show a higher current density for the oxidation of ammonia, than the treated particles. The decay of the current after the potential cycling was greater with the non-treated particles than on the particles, which were subjected to the square wave treatment. The chronoamperometry traces reflects similar behaviors.
Effect of the Kind of the Cathode Catalyst on the Cell Performance under Low and High Relative Humidity
Authors: Nakajima Hitoshi , Matsutani Koichi , Kaieda Takeshi , Tada Tomoyuki
Published: October 2010

The cell performances under low or high relative humidity were examined for Pt / C cathode catalysts of various kinds of carbon support. No significant difference of cell performance were observed among Vulcan XC-72, Graphitized Vulcan XC-72, HSAC-1 (Surface Area = c.a. 800 m2 g-1, particle size = c.a. 30 nm), and HSAC-2 (Surface Area = c.a. 800 m2 g-1, particle size = c.a. 10 nm). Heat treatment process to improve the stability decreased the cell performance especially under low relative humidity. It was suggested by the titration of catalysts that the loss of hydrophilic organic group on the surface of carbon support by the heat treatment of catalysts was one of the reasons. The effect of the weight ratio of ionomer to carbon (I / C) was also examined. For example, in the case of Vulcan XC-72 support, the best I / C for the cell performance was 0.9.
Effect of Core Size on Activity and Durability of Pt Core-Shell Catalysts for PEFCs
Authors: Inaba Minoru , Ito Hiroyuki , Tsuji Hiroaki , Wada Tetsuro , Banno Michiko , Yamada Hirohisa , Saito Morihiro , Tasaka Akimasa
Published: October 2010

Pt/Au/C and Pt/Pd/C core-shell catalysts were prepared from Au/C and Pd/C cores with different core sizes using under potential deposition (UPD) of Cu, and the activity for oxygen reduction reaction and durability of the Pt/Au/C and Pt/Pd/C catalysts were investigated. Pt/Au/C and Pt/Pd/C core-shell catalysts showed higher mass activities than a commercially available Pt2.8nm/C catalyst, and hence they are promising for reducing the Pt usage in PEFCS. In potential cycling durability tests between 0.6-1.0 V, opposite effects of core size on were observed for Pt/Au/C and Pt/Pd/C. For Pt/Au/C, smaller cores gave high durability, whereas for Pt/Pd/C, larger cores gave high durability comparable with the Pt2.8nm/C.
Development of Low Pt Loading Cathode Catalysts for Polymer Electrolyte Membrane Fuel Cells
Authors: Li Xuguang , Huang Sheng-Yang , Popov Branko N.
Published: October 2010

The objective of this work is to develop low Pt loading oxygen reduction catalysts with high activity and good stability, which are essential for DOE's mission for next generation fuel cells. Two strategies are pursued: (1) The first approach involves the creation of hybrid cathode catalysts (HCC) that are a combination of N- containing carbon composite catalysts (CCC) developed at USC with platinum for oxygen reduction. Besides its own contribution to the overall catalyst activity (an advantage over conventional carbon black supports), the CCC can enhance the activity of the Pt through synergistic effects. (2) The second strategy involves the use of corrosion-resistant TiO 2 as a catalyst support for Pt to eliminate high degradation rate of the standard carbon support. The TiO 2 with high surface area is developed at USC, which is superior to carbon support in terms of stability at high potentials. Our preliminary experimental results demonstrate that the proposed strategies are very promising in scientific and engineering aspects for developing low Pt loading cathode catalysts.
Testing of Catalyst Coated Membranes for PEMFC, Prepared by Electrospray Deposition
Authors: Chaparro Antonio M. , Alonso-Álvarez Irene , Ferreira-Aparicio Paloma , Folgado M. Antonia , Martín Antonio J. , Daza Loreto
Published: October 2010

Catalyst layers deposited on the membrane are compared with similar layers deposited on the gas diffusion layer (GDL), using the electrospray deposition method. The objective double: first, to explore the viability of this method for 'on membrane' deposition of Pt/C+Nafion films, and, second, to know the differences in single cell performance that this procedure introduces with respect to the 'on GDL' deposition. It is found that electrospray deposition is able to produce 'on membrane' deposited catalyst layers with good adherence. In addition, on membrane deposited cathodic catalyst layers have superior performance in single cells, compared with the same films deposited on the GDL. The analysis of polarization curves shows that the improvement is due to a decrease in the internal resistance of the cell, whereas electrocatalytic activity and active area maintain unchanged. The lower internal resistance corresponds to a decrease in the high frequency contribution (1 kHz), so it appears to indicate that on membrane deposition improves the fast ionic conduction processes at the cathodic catalyst layer-membrane interface. The good performance of electrospray deposited catalyst layers shown in previous works, and the possibility for on-membrane deposition demonstrated here, opens a new way to prepare PEMFC electrodes with high efficiency and low catalyst loading.
Bulk and Surface Compositions of PtRu Catalysts and Their Methanol Oxidation Activity and Durability
Authors: Onodera Taigo , Suzuki Shuichi , Takamori Yoshiyuki , Daimon Hideo
Published: October 2010

A controlled synthetic scheme of PtRu catalyst for methanol oxidation reaction is reported. PtRu catalyst was obtained by using an electroless plating method with chelate ligands. The well-mixed PtRu catalyst synthesized with chelate ligands (PtRu/C WCL) showed higher methanol oxidation reaction activity and stability relative to those of PtRu catalyst synthesized without chelate ligands (PtRu/C WOCL).
Enhanced Activity of Ir-V as Anode Catalyst for PEMFC at Elevated Temperature
Authors: Yang Daijun , Li Bing , Tao Kan , Lv Hong , Zheng Jun-Sheng , Ma Jianxin
Published: October 2010

Using shorter side chain perfluorosulfonic acid (PFSA) membrane, PEMFC can be operated at elevated temperature up to 95åC. Five synthesized catalysts, with different Ir:V ratios, made via an ethylene glycol (EG) method were used as the anode catalysts respectively, with a loading of 0.4 mg (Ir) cm-2. With 40%Ir-10%V anode catalyst, the highest power density, 728 mW cm-2, can be reached under 95åC for a 50cm2 H2/air single cell. This is much higher than that with Pt/C as the anode catalyst and this trend is further proved by linear sweep voltammetry (LSV). XRD patterns show that mean 2.7nm particle size has been obtained, and the addition of V to Ir/C may decrease the lattice parameter of Ir (fcc) crystal.
Platinum Nanoparticles Supported on N-Functionalized Mesoporous Carbon
Authors: Shrestha Sujan , Mustain William E.
Published: October 2010

A modified polyol process was used to deposit platinum nanoparticles on nitrogen functionalized ordered mesoporous carbon. The pH was adjusted to control the platinum size and loading. Several physical characterization tools were used to determine the size, dispersion and structure of the catalyst and support including X-ray Photoelectron Spectroscopy, X-ray Diffraction, and high resolution transmission electron microscopy. The electrochemically active area for the oxygen reduction reaction was computed by cyclic voltammetry. Platinum deposited on nitrogen functionalized ordered mesoporous carbon was found to have higher dispersion and utilization than platinum deposited on Vulcan XC-72R.
A Combined Rotating Disk Electrode/X-ray Diffraction Study of Co Dissolution from Pt1-xCox Alloys
Authors: Stevens David , Wang Stephen , Sanderson Robbie , Liu Gary C. , Vernstrom George D. , Atanasoski Radoslav T. , Debe Mark K. , Dahn Jeff
Published: October 2010

The oxygen reduction activity of a series of Pt1-xCox catalysts (with high Co content) sputter-deposited onto 3M's nano-structured thin film support was measured with Rotating Disk electrode techniques. The activity was found to be much higher than that measured on Pt only. It was however not stable with repeated potential cycling. Ex-situ x-ray diffraction measurements of the disks during testing showed loss of bulk Pt from the lattice.
EQCM Study of the Electrodeposition of Pt-WO3 and Its Catalytic Activity towards the ORR
Authors: Martín Antonio J. , Chaparro Antonio M. , Daza Loreto
Published: October 2010

The electrodeposition process of WO3 and Pt-WO3 from acid solution has been investigated by means of Electrochemical Quartz Crystal Microbalance. Cyclic potential sweeps on Au substrate show that WO3 is a complex process with at least 5 different growth regimes, combining electrochemical and non electrochemical processes. Substoichiometric oxides and bronzes formation are involved in the deposition processes. When both Pt and WO3 precursors are present, Pt deposition is favoured and interaction between Pt and WO3 bronzes may explain this behaviour. Oxygen reduction (ORR) experiments on Pt-WO3 electrodeposited on glassy carbon and WO3 reveal high catalytic activity compared with platinum alone.
Effect of Surface Composition of Platinum-Ruthenium Nanoparticles on Methanol Oxidation Activity
Authors: Suzuki Shuichi , Onodera Taigo , Kawaji Jun , Mizukami Takaaki , Takamori Yoshiyuki , Daimon Hideo , Morishima Makoto
Published: October 2010

Methanol oxidation activity of platinum-ruthenium nanoparticles on carbon supports was investigated as a function of the surface platinum-ruthenium composition. The surface composition of the platinum-ruthenium nanoparticles was measured with a technique combining copper under potential deposition and copper stripping. The measurements showed that the surface composition was not the same as the bulk composition even though X-ray diffraction analysis showed that all the platinum-ruthenium nanoparticles formed a solid-solution alloy. The methanol oxidation activity of the platinum-ruthenium nanoparticles was measured by linear sweep voltammetry using a rotating disk electrode in a 0.5 mol/l sulfuric acid solution containing 1.0 mol/l methanol at 308 K. This electrochemical analysis showed that the methanol oxidation activity did not correlate with the bulk composition but with the surface composition. Moreover, in the case of platinum-ruthenium nanoparticles, the maximum methanol oxidation activity was observed at a surface platinum-ruthenium composition of around 50 at.% ruthenium.
Structure-Activity Relationship of Dealloyed PtCo3 and PtCu3 Nanoparticle Electrocatalyst for Oxygen Reduction Reaction in PEMFC
Authors: Oezaslan Mehtap , Hasché Frédéric , Strasser Peter
Published: October 2010

We report a synthesis and study on carbon supported PtCo3 and PtCu3 alloy nanoparticle catalyst for ORR. The chemical composition of alloys was carried out with EDS. The electrochemical measurements were conducted using a thin-film RDE method. Recently, we have demonstrated that dealloyed PtCu3 nanoparticle exhibits 3-4 times higher mass activity and 4 times higher specific activity for ORR than Pt. Here, the dealloyed PtCo3 also shows about 4 fold increase in specific activity, but 2-3 fold in mass activity than Pt/C. The in-situ generated Pt rich surface of Co rich Pt alloy nanoparticle catalyst tested for ORR activity. Geometric effects based on Pt surface constitution were assumed for the high activity for ORR. PtCo3 nanoparticle catalyst seems to be an interesting opportunity for further studies for ORR. The thermodynamic instable deposition of Co and the robust Pt ECSA are probably the large advantages to other Pt alloys.
New Ir-V-W Electro-Catalyst Exceeding Pt for the Anode of Fuel Cells
Authors: Li Bing , Qiao Jinli , Yang Daijun , Wang Haijiang , Ma Jianxin
Published: October 2010

Very active catalysts 40%Ir-10%V-3%W/C and 40%Ir-10%V-10%W/C, as a novel suitable anode catalyst in PEMFCs, have been synthesized by an ethylene glycol reduction method. The nanostructured catalysts have been characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (TEM). Ir nanoparticles, after modification with V and further with W, show a narrow particle size distribution centered at 2 nm, and are uniformly dispersed on Vulcan XC-72. Investigation of the catalytic activity by means of linear sweep voltammetry (LSV) employing a rotating disk electrode (RDE) has revealed that 40%Ir-10%V-3%W/C catalyst exhibited very high electrocatalytic activity in terms of hydrogen oxidation reaction (HOR). About 76% higher current density was obtained for 40%Ir-10%V-3%W/C compared to that of 40%Pt/C except for 320% higher current density compared to that of the pure 40%Ir/C at 0.1 V versus RHE. The performance of a membrane electrode assembly (MEA) prepared with the 40%Ir-10%V-3%W/C as the anode catalyst generated a maximum power density of 625.9mW cm-2 at 0.59 V and 70 oC, which is 32% higher than that of commercial available 40%Pt/C.
Model Electrode Structures for Studies of Electrocatalyst Degradation
Authors: Goeke Ronald S. , Datye Abhaya K. , Atanassov Plamen , St-Pierre Jean
Published: October 2010

Model Pt catalyst structures have been fabricated directly on planar glassy carbon electrodes by physical vapor deposition. Application of these model electrodes toward the understanding of fuel cell catalyst degradation is demonstrated. These model electrodes are further improved with the development of a templated synthesis process to create Pt nanoparticle arrays of controlled size and spacing. The catalysts are characterized by scanning electron microscopy and rotating disk electrode experiments. Surface area loss from potential cycling is demonstrated with mechanisms of sintering, dissolution and particle detachment.
New Understanding of Pt Surface Area Loss in PEMFC's: Temperature Effects
Authors: Holby Edward F. , Shao-Horn Yang , Sheng Wenchao , Morgan Dane
Published: October 2010

Loss of nanoparticle surface area under polymer electrolyte membrane fuel cell (PEMFC) operating conditions is an important barrier to the practical application of PEMFCs. We have developed an electrochemical rate theory model to better understand a number of aspects of Pt surface area loss, including the effects of particle size distribution, crossover molecular hydrogen, and Pt oxidation. As a specific example we here discuss some initial efforts to understand the effects of temperature on Pt nanoparticle stability. We compare our results to a previously developed first-order kinetic model and use this comparison to evaluate the role of the kinetic activation enthalpy for Pt dissolution and precipitation on overall surface area loss.
Mechanism of Coupled Transport in the Coarsening of Platinum under Stress in Nonaqueous Electrolyte
Authors: Parthasarathy Preethy , Virkar Anil
Published: October 2010

Effect of mechanical stress on platinum dissolution was measured. The procedure consisted of immersing two platinum wires/foils in PtCl4 solution in DMSO. A tensile stress was applied to one of the wires/foils, while the other one was left stress-free. It was observed that wire/foil subjected to tensile stress became electrically positive, consistent with lowering of platinum chemical potential. The voltage measured varied linearly with applied stress. The measured voltage difference is in good agreement with theory. When shorted externally, the wire/foil under tensile stress thickens while the unstressed one shrinks, consistent with Pt transport from unstressed wire/foil to stressed (tensile) wire/foil. The process involves coupled transport of platinum ions through electrolyte and electrons in the external circuit. The results demonstrate the role of stress on dissolution/precipitation of Pt. Implications of the results for PEMFC catalyst degradation and the design of degradation-resistant core-shell catalysts are discussed.
Chemical Fingerprint Associated with the Formation of Pt in the Membrane in PEM Fuel Cells
Authors: Susac Darija , Wang Jian , Martin Zulima , Hitchcock Adam , Stumper Jürgen , Bessarabov Dmitri
Published: October 2010

In this study, localized chemistry around Pt crystals formed in the membrane in an end-of-life (EOL) fuel cell catalyst coated membrane (CCM) was studied using near edge X-ray absorption spectra (NEXAFS) recorded with scanning transmission X-ray microscopy (STXM). X-ray Photoelectron spectroscopy (XPS) was applied to analyze the composition of the cathode catalyst powder used to prepare the CCMs. The XPS data indicated the presence of N-containing impurities within the catalyst powder with N 1s peak position consistent with a majority of NHx but also minority nitrate and nitrite environments. The region around the Pt particles in the membrane of EOL samples had N 1s near edge X-ray absorption spectra similar to those from the cathode catalyst and not from the membrane or the embedding epoxy. The results suggest the involvement of an unreduced Pt- N containing ligands -complex in the formation of Pt in the membrane.
Influence of PEMFC Operating Conditions on the Durability of Pt3Co/C Electrocatalysts
Authors: Dubau Laetitia , Durst Julien , Maillard Frédéric , Chatenet Marian , André Johan , Rossinot Elisabeth
Published: October 2010

This work is dedicated to the characterization of structure and composition change of the membrane electrode assembly (MEA) upon on-site proton-exchange membrane fuel-cell (PEMFC) operation (constant current load and start/stop conditions), with special emphasis on the Pt3Co/C cathode electrocatalyst. A fast degradation of the cathode catalytic layer was monitored. It yielded to the redistribution of both Pt and Co elements within the whole MEA, decrease of the MEA thickness and a continuous leaching of the surface/bulk Co atoms. The cell performance decay is discussed in the light of these changes.
Development of Catalysts with Enhanced Tolerance to Fuel Cell Transient Conditions
Authors: Stevens David , Sanderson Robbie , Hatchard Tim , Crowtz Tim , Dahn Jeff R. , Vernstrom George D. , Haugen Gregory M. , Watschke Terri , Atanasoska L. L. , Atanasoski Radoslav T.
Published: October 2010

A Ru1-xIrx binary over-layer was deposited on Pt-coated nano-structured thin film from 3M Company. XPS measurements were used to confirm the composition of the over-layer. Rotating disk electrode measurements were used to assess oxygen evolution activity of the catalysts. The results showed that a low Ir/high Ru over-layer had a higher activity but lower stability than high Ir/low Ru samples.
Structural and Morphological Properties of Carbon Supports: Effect on Catalyst Degradation
Authors: Patel Anant , Artyushkova Kateryna , Atanassov Plamen , Young Alan P. , Dutta Monica , Ahmad Zaid , Colbow Vesna , Wessel Silvia , Ye Siyu
Published: October 2010

The object of this work was to identify correlations between performance losses of Pt electrocatalysts on carbon support materials and the chemical and morphological parameters that describe them. Accelerated stress testing, with an upper potential of 1.2 V, was used to monitor changes to cathode properties, including kinetic performance and effective platinum surface area losses. The structure and chemical compositions were studied using X-ray Photoelectron Spectroscopy and Scanning Electron Microscopy coupled with Digital Image Processing. As this is an ongoing study, it is difficult to draw firm conclusions, though a trend between support surface area overall performance loss was found to exist.
Alternative Electrocatalyst Support Materials for Polymer Electrolyte Fuel Cells
Authors: Sasaki Kazunari , Takasaki Fumiaki , Noda Zhiyun , Hayashi Shingo , Shiratori Yusuke , Ito Kohei
Published: October 2010

Durability of electrocatalysts under severe operational conditions of polymer electrolyte fuel cells (PEFCs) is one of the most important technological issues to be improved. Alternative electrocatalyst support materials are desired, the use of which may solve problems such as oxidation-induced carbon support corrosion. One interesting solution is to use conductive oxide-based catalyst support. We focus our attention to SnO2, known as an oxide semiconductor with a high electronic conductivity. Nano-carbon support materials are also studied as an another option of electrocatalyst support design. Technical merits and remaining issues in alternative electrocatalyst support materials selection are discussed.