bluuebunny/crossref_metadata_2025 huggingface dataset:
Imaging the Electrode-GDL Interface by a Modified Wood's Intrusion Process
Authors: Scheiba Frieder , Kunz Ulrike , Butsch Hanno , Zils Susanne , Fuess Hartmut , Roth Christina
Published: October 2010

The structure of the interface between the gas diffusion layer (GDL) and the electrode is extremely important for the fuel cell's performance. However, although numerous methods exist for the analysis of either the GDL or the membrane-electrode assembly (MEA), not many techniques render themselves suitable for the simultaneous imaging of both components. Electron microscopy would be an option, but the preparation of cross-sections is extremely demanding due to the materials' different mechanical properties. This paper presents a sample preparation technique using the intrusion with low-melting Wood's metal, which stabilizes the porous GDL-electrode interface and enables its cutting into thin sections. Using this alternative approach, a considerable influence of the structure of the GDL on the electrode morphology could be demonstrated. In regions, where the fiber bundles from the backing recede from the membrane, delamination occurs more frequently. Furthermore, penetration of the MPL into the carbon fiber backing was observed.
Multiphysics Simulation of Hydrogen PEM Fuel Cell
Authors: Mukherjee Shiladitya , Gidwani Ashok , Roy Abhra , Cole J. Vernon , Jain Kunal , Bapat Chaitanya , Thoms Richard
Published: October 2010

In this paper, we present our continued development of an Eulerian two-fluid model to simulate multiphase water transport in the porous membrane, electrode and gas channel of the Proton Exchange Membrane Fuel Cell (PEMFC). The model includes advanced flow physics relevant to fuel cell operation. The formulation allows incorporation of liquid gas drag models to capture the effect of phase segregation leading to formation of films and slugs in the flow channels. The porous media is modeled to include drag from the porous solid and capillary forces. Interactions between the liquid water and MEA electrochemistry with detailed Butler-Volmer kinetics are also implemented. Furthermore, the energy equation is integrated to facilitate evaluation of temperature distribution and its effect on water transport. Model capability is demonstrated by comparing with experimental and model data from the literature.
Multiscale Simulation of Single-Phase Multicomponent Transport in the Cathode Gas Diffusion Layer of a Polymer Electrolyte Fuel Cell
Authors: Rama Pratap , Liu Yu , Chen Rui , Ostadi Hosein , Jiang Kyle , Zhang Xiaoxian
Published: October 2010

A feasibility study into the development and application of a single-phase multi-component (SPMC) lattice Boltzmann (LB) model to simulate the movement of a three-species gas through the cathode gas diffusion layer (GDL) of a polymer electrolyte fuel cell (PEFC) has been reported in this paper. The porous geometry of the GDL is captured and digitally reconstructed for the numerical model using X-ray computed micro-tomography. The boundary conditions at the channel and catalyst layer interfaces for the SPMC-LB simulations including species partial pressures and through-plane flow rates are obtained using a previously-developed and validated electrochemical model of the complete multi-layer PEFC, which is based on the general transport equation (GTE). The results reveal that the SPMC-LB model has the capability to precisely detail the distribution of multi-species gas components through the heterogeneous porous structure of the GDL.
La2O3-Modified Nickel-Cobalt Composite Coating as Cathode Materials for Hydrogen Evolution Reaction
Authors: He Ping , Liang Yan , Chen Yatao , Yi Xiaofang , Du Licheng , Dong Faqin
Published: October 2010

La2O3 was successfully doped into nickel-cobalt alloy coating on Ti substrate by electrodeposition technology. The surface morphology and microstructure were examined by SEM and XRD, respectively, and the hydrogen evolution property was evaluated by electrochemical techniques, including steady-state polarization, Tafel plot and electrochemical impedance spectroscopy. It was found that the incorporated La2O3 particles resulted in the improvement of roughness and surface area of the composite coating electrode, and hydrogen evolution potential of nickel-cobalt-La2O3 composite coating electrode moved positively around 178 mV at 15 mA cm-2 compared with that of nickel-cobalt alloy deposited coating electrode. It was assumed that the enhanced electrocatalytic activity to hydrogen evolution was attributed to the improved surface area and the decreased apparent activation energy, which was verified by hydrogen evolution kinetics parameters calculated from Tafel plots and electrochemical impedance spectroscopy.
Y2O3-Modified Ni-Co Composite Coating as Cathode Materials for Hydrogen Evolution Reaction on Titanium Substrate
Authors: Yi Xiaofang , He Ping , Chen Yatao , Wang Wei , Yang Dingming , Dong Faqin
Published: October 2010

Ni-Co-Y2O3 composite coating was prepared by electrodeposition from an electroplating bath containing a suspension of Y2O3. The morphology and microstructure in view of their possible application as electrocatalytic materials for the hydrogen evolution reaction were characterized by SEM and XRD, respectively. The electrocatalytic efficiency was evaluated on the basis of steady-state polarization, Tafel curves and electrochemical impedance spectroscopy measurements carried out in 0.50 M Na2SO4 + 0.10 M H2SO4 solution. It was found that hydrogen evolution reaction proceeded better in the presence of Y2O3. The hydrogen evolution potential of Ni-Co-Y2O3 composite electrode moved positively about 100 mV at 13 mA cm-2 compared with that of Ni-Co alloy electrode.
Bimetallic Electrocatalysts Supported on TiO2 for PEM Water Electrolyzer
Authors: Fuentes Roderick E. , Rau Sebastian , Smolinka Tom , Weidner John W.
Published: October 2010

TiO2 was investigated as a support for several multi-metallic electrocatalysts. Particle size distribution from High Resolution Transmission Electron Microscopy (HRTEM) images showed less than 2 nm average particle sizes. For unsupported Ir-Ru, HRTEM images showed nanoparticles closer than supported Ir-Ru on anatase TiO2 that tend to agglomerate. The electrocatalysts supported on anatase TiO2 showed higher activity towards the oxygen evolution reaction (OER) than those supported on rutile TiO2. Overall, Ir-Ru had the highest current per gram of metal than other metal combinations studied and the optimum ratio was 1:1 Ir:Ru. For the unsupported case, the OER activity was about 41% lower than supported.
Ab Initio Study of Doped Tin Niobates and Tantalates as Prospective Catalyst Supports for Water Electrolysis
Authors: Velikokhatnyi Oleg , Kumta Prashant
Published: October 2010

The electronic structure of Sn2Ta2O7, Sn2Nb2O7, SnTa2O6, and SnNb2O6 compounds doped with small amounts of As, Sb, Bi, Cr, Mo, and W has been calculated in an attempt to identify new electrochemically stable viable catalyst supports for water electrolysis. Vienna ab-initio simulation package (VASP), within the projector augmented-wave (PAW) method in the general gradient approximation (GGA) for conducting the exchange-correlation corrections, has been utilized for the calculations. The role of doping 5A- and 6B-elements in improving the electronic conductivity has been discussed. Discussion of the cohesive energies for the materials and their electronic conductivity indicates that the thoreaulite structure of SnTa2O6 doped with As, Sb, or Bi could be the most appropriate candidates for use as catalyst supports in water electrolysis.
Quantification of Voltage Loss in the PEM Reactor for Electrolyzing Hydrogen Bromide to Produce Hydrogen
Authors: Zhang Rui , Weidner John W.
Published: October 2010

Simultaneous conversion of gaseous hydrogen bromide to bromine and hydrogen can be accomplished in a Proton Exchange Membrane (PEM) electrolyzer. The cell voltage required to carry out this conversion is a function of design and operating conditions. The cell voltage is composed of the equilibrium cell potential as well as individual potential losses in the cell (e.g. ohmic, activation, mass transfer etc). All these potential contributions are greatly influenced by the water content in the membrane and at the catalytic surface. Therefore, it is necessary to accurately predict the water transport across the cell to quantify the individual voltage losses. The equilibrium cell potential is predicted by Nernst equation coupled with vapor-liquid equilibrium (VLE) calculations for the Br2-HBr-H2O and H2-H2O system. The model for predicting the total cell potential shows good agreement to the data over a range of current densities.
Carbon-Free Hydrogen Production in a Steam-Carbon Electrochemical Cell
Authors: Alexander Brentan R. , Lee Andrew , Mitchell Reginald , Gür Turgut
Published: October 2010

This study describes a novel electrochemical approach for the simultaneous and spontaneous production of carbon-free hydrogen and electricity. Hydrogen was generated from steam at the cathode of a yttria stabilized zirconia electrolyte by utilizing a solid carbonaceous fuel at the cell anode to maintain low oxygen activity levels within the anode chamber. The results verified that a steam-carbon cell is capable of producing carbon-free hydrogen in a fuel cell mode while generating electric power at the same time. The open circuit voltages of the cells agreed with expected values. The current-voltage behavior indicated that cell performance was governed mostly by resistive losses. A gas transport model of the solid carbon bed based on known Boudouard kinetics was developed and analyzed. The model demonstrates that the fuel bed is capable of supporting a cell current density in excess of 700 mA/cm2 while maintaining a fuel utilization rate of over 85%.
Origin of Polarization Losses in Solid Oxide Electrolysis Cells under High Current Density
Authors: Knibbe Ruth , Ebbesen Sune D. , Mogensen Mogens
Published: October 2010

Under high current density, polarization losses in a solid oxide cell are higher in electrolysis mode than in fuel cell mode. Although part of these differences under high current density can be attributed to gas diffusion differences between steam and hydrogen. Diffusion coefficient differences can only partially explain the higher polarization losses during electrolysis operation.
Modeling and Evaluation of a Photoelectrochemical Reactor for H2 Production
Authors: Carver Christopher , Ulissi Zachary , Ong Chin Kin , Dennison Stephen , Hellgardt Klaus , Kelsall Geoff H.
Published: October 2010

A model for the operation of a working photoelectrochemical reactor has been developed and implemented, using the COMSOL MultiphysicsTM modeling package. The model incorporates the detailed design of the practical reactor developed to use a 0.01 m2 Fe2O3 photoelectrode. Initial modeling was used to analyze electrolyte flow within the reactor and recommend modifications to the reactor design. Results indicate that improvements to flow uniformity could be achieved with some minor internal changes. Modeling results confirmed that, under normal operating conditions, bubble formation occurs across the whole photoanode and potentially fills a dead zone in the reactor. The effect of the sheet resistance of the transparent conducting oxide substrate (fluorine-doped tin oxide) on potential and current distribution across the photoanode has also been calculated. This shows that for the 0.01 m2 photoanode used in this work, potential drop across the photoanode results in large areas of the photoanode becoming inactive to oxygen evolution.
Conductive Polymer-Titania Photocathode Development for Hydrogen Production
Authors: Bruce David , Wilkinson David
Published: October 2010

Polybithiophene and polybithiophene-titania films were electropolymerized under galvanostatic conditions on carbon fibre paper substrates and tested under AM1.5G conditions in 0.5 mM H2SO4 in order to evaluate their catalytic performance, their photonic conversion efficiency, as well as their Faradaic photoelectrochemical performance for hydrogen generation. The electrochemical data indicates that the films were stable and showed promise as a viable photocathode material as they significantly reduced the cathodic overpotential needed to promote hydrogen generation up to a current density of 75 µAcm-2. The photonic efficiency was low and showed a maximum incoming photonic conversion efficiency (IPCE) at a current density of 240 µAcm-2. Substrate considerations such as sub-micron architectural variables should be further investigated alongside film thickness and nanoparticle composition to optimize the photonic and catalytic performance.
In Search of Efficient Anode and Cathode Materials for Double Junction Amorphous Silicon Solar Cell Driven all Solar Electrolysis of Water to Hydrogen and Oxygen Gases
Authors: Frites Mourad , Ingler William B. , Khan Shahed U.
Published: October 2010

Few non-noble metal based anode and cathode materials were investigated for all solar electrolysis of water to hydrogen and oxygen gases powered by double junction amorphous silicon (Dj-a-Si) solar cell under solar simulated light of 1 sun. The highest hydrogen generation current efficiency of 58.68 % was obtained when Pt wire was used as a cathode with the non-noble metal based Ni-Co3O4 as an anode in the electrochemical cell. However, when Pt metal was replaced by a non-noble metal Ni the maximum hydrogen generation current efficiency of 51.28 % was observed. Comparable hydrogen generation current efficiencies were found when Ni-Co3O4 anode or thin RuO2 coated Ti metal anode (RuO2-Ti) was used in combination with Pt metal cathode. The percent solar to hydrogen conversion efficiencies (% STH) were found to be 8.66 % and 8.46 % for the Dj-a-Si solar cell driven electrolysis of water in the Ni-Co3O4||Pt and RuO2-Ti||Pt electrochemical cells respectively. For non-noble metal based electrochemical cell, Ni-Co3O4||Ni the % STH efficiency was found to be 7.57 %.
Electrocatalytic Activity of Ta Compound Thin Film for Oxygen Reduction Reaction
Authors: Matsuzawa Koichi , Kikuchi Akifumi , Ishihara Akimitsu , Mitsushima Shigenori , Ota Kenichiro
Published: October 2010

In order to understand the catalytic activity for the oxygen reduction reaction (ORR) of Ta compound film, a thin film catalyst using TaC or TaN target by magnetron sputtering under Ar+N2+O2 mixture was prepared and investigated the effects of the target material, the temperature of base material and gas composition on the catalytic activity for the ORR. Thin films of Ta compound prepared from TaC target was better than that from TaN target for the ORR. The optimum preparation condition of TaCxNyOz was in the oxygen partial pressure range from 10 to 15 mPa with a certain partial pressure of N2. TaCxNyOz of high ORR activity was mainly consisted of TaON. The main difference between TaCxNyOz and TaOxNy prepared from TaN target was the carbon content on the surface.
Electrochemical Oxygen Reduction on Carbon Nitride
Authors: Lyth Stephen M. , Nabae Yuta , Islam Nazrul M. , Kuroki Shigeki , Kakimoto Masa-aki , Ozaki Jun-ichi , Miyata Seizo
Published: October 2010

Electrochemical oxygen reduction via non-precious, Fe-macrocycle-derived catalysts has potential to reduce the cost and increase acceptance of hydrogen-powered polymer electrolyte membrane fuel cells. However since these materials are a complex mixture of carbon, nitrogen and iron, the nature of the active site is still much debated. By using carbon nitride as an ideal, nitrogen-rich, iron-free catalyst we shed light on the role of carbon-nitrogen bonding in electrochemical oxygen reduction. Carbon nitride was synthesized on a carbon black support via a simple solvothermal process. The resulting material was pyrolyzed and characterized via a variety of techniques. Electrochemical testing revealed that carbon nitride pyrolyzed at 1000åC displayed the best oxygen reduction activity, with an onset potential of 0.90V and a low selectivity to H2O2 formation, indicating a 4-electron oxygen reduction pathway. The enhanced activity is attributed to enriched quaternary nitrogen in the material at this temperature, as confirmed by X-ray photoelectron spectroscopy.
Electrochemical Studies of N-Functionalized Mesoporous Carbon
Authors: Shrestha Sujan , Mustain W.
Published: October 2010

Nitrogen functionalized ordered mesoporous carbon was synthesized using pyrrole as the precursor and SBA-15 as the template, and its physical and electrochemical properties were investigated. Highly ordered mesoporus carbon with high nitrogen content (C/N = 8.3) was obtained. Physical properties were elucidated using transmission electron microscopy, Brunauer-Emmett-Teller N2 adsorption, attenuated total reflectance fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The resulting material was found to have a specific capacitance of 182.5 F/g. Also, the oxygen reduction reaction activity and corrosion resistance was superior to that of Vulcan XC-72R.
Improved Synthesis Method for a Cyanamide Derived Non-Precious ORR Catalyst for PEFCs
Authors: Hsu Ryan S. , Chen Zhongwei
Published: October 2010

Non-noble catalysts synthesized using an iron salt, cyanamide and Ketjen Black EC-600JD were developed as ORR active Fe-N/C materials for PEFC applications. The resulting initial Fe-cyan-KJ600 catalyst demonstrated poor ORR performance, however, through the addition of NH3 during the pyrolysis treatment, and by modifications of the synthesis procedure to include a second coating and pyrolysis stage, the ORR performance increased drastically. The present study utilizes X-ray diffraction, scanning electron microscopy, nitrogen adsorption/desorption, and electrochemical analysis in characterizing the synthesized samples to determine the morphological and electrochemical effects of the aforementioned treatment steps.
Fe-N/C Oxygen Reduction Catalysts Prepared by Surface Functionalization of Carbon Black with 5,6-diamino,1-10-phenanthroline
Authors: Pauric Allen D. , Easton E. Bradley , MacLean Brian J.
Published: October 2010

Non-precious metal catalysts (NPMC) for the oxygen reduction reaction were prepared by surface modification of a carbon black (Black Pearls 2000) with 5,6-diamino-1,10-phenanthroline through diazonium and benzimidazole coupling chemistry. Both methodologies covalently attach 1,10-phenanthroline to the surface. Cyclic voltammetry of these modified carbons show a clearly defined redox peak at ca. 650 mV vs. NHE that is often observed for many NPMCs. We attribute this peak to phenanthroline type groups on the carbon surface. Introduction of Fe and subsequent pyrolysis at 700oC under a NH3/N2 atmosphere yielded catalysts that were highly active towards the oxygen reduction reaction (ORR). Neither methodology produced a catalyst that was significantly more active than the other.
Sm0.5Sr0.5CoO3 Electrodes Fabricated at Intermediate Temperatures
Authors: Koep Erik , Morante J.R.
Published: October 2010

Thick film SSC cathodes were fabricated by combustion CVD and evaluated via impedance spectroscopy. Films were deposited onto 250 micron YSZ at fabrication temperatures of 1000°C, 600°C and 450°C. Deposition temperature affected both the microstructure and phase of the resulting films but not their chemical composition. SSC electrodes fabricated at 450°C were aglomerations of largely amorphous particles while those fabricated at higher temperatures were interconnected polycrystalline films.
Hydrophilic-Hydrophobic Character of DMFC Cathode Catalyst Layers
Authors: Capitanio Francesca , Tavares Ana
Published: October 2010

DMFC composite cathodes, prepared from a 60 wt% Pt/Vulcan catalyst and by simultaneous deposition of Nafion and PTFE binders, were characterized in oxygen and nitrogen saturated H2SO4 0.5M solution by means of cyclic voltammetry and electrochemical impedance spectroscopy. The results showed the importance of the simultaneous presence in the catalyst layer structure of the hydrophilic and hydrophobic components, to provide the paths for the proton conduction and for the continuous supply of oxygen to the active sites.
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 R. , 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 and deposited on the working electrode (glassy carbon) substrate modified with Cs2.5H0.5PW12O40 mixed with Vulcan XC-72 carbon nanoparticles. 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) towards oxygen reduction. It is expected that Pt is located inside pores of Cs2.5H0.5PW12O40. Reactivity of Pt-free Cs2.5H0.5PW12O40 system towards reduction of hydrogen peroxide has also been addressed.
Nanoporous Carbon-Supported Fe/Co-N Electrocatalyst for Oxygen Reduction Reaction in PEM Fuel Cells
Authors: Choi Ja-Yeon , Hsu Ryan S. , Chen Zhongwei
Published: October 2010

As a substitute for high-cost platinum based catalysts, nonprecious catalysts for the oxygen reduction reaction were synthesized by deposition of Fe/Co-N composite onto two different nanoporous carbon supports, Ketjen Black EC300J and EC600JD, using ethylenediamine as a nitrogen precursor. Rotating ring disk electrode measurements were used to investigate the ORR activity, and the results obtained from EC600JD based catalyst, showed improved onset and half-wave potentials and superior selectivity than that of the EC300J. Similarly, the catalyst showed good performance in the hydrogen-oxygen PEMFC, being able to produce 0.37 A/cm2 with a maximum power density of 0.44 W/cm2 at a cell voltage of 0.6 V. A fuel cell life test at a voltage of 0.40 V demonstrated promising stability up to 100 h. These results suggest that a higher pore volume and surface area of the carbon support could lead to higher nitrogen content, providing more active sites for ORR.
Modeling the Effect of Low Carbon Conductivity of the Cathode Catalyst Layer on PEM Fuel Cell Performance
Authors: Baghalha Morteza , Stumper Jürgen , Harvey David , Eikerling Michael
Published: October 2010

Carbon corrosion is a major degradation mechanism in cathode catalyst layers (CCL) of PEM fuel cells. Carbon corrosion causes carbon particles to decrease in size and the ionomer to carbon ratio to increase. One of the consequences of these changes is the reduced electronic conductivity of the carbon phase in CCL. In the present study, the effect of reduced carbon conductivity on the cell performance was investigated through modeling of two experimental case studies of a fresh and a severely degraded CCL. The critical carbon conductivity of CCL, below which the electronic potential loss in a degraded CCL becomes an important contributing loss, is defined. The inter-relations between low carbon conductivity, electronic ohmic loss, and EPSA loss (through Pt/C particles detachment mechanism) are also discussed.
Polarization Resistance of La0.85Ca0.15MnO3 Cathodes for Solid Oxide Fuel Cells (SOFCs) Measured Using Patterned Electrodes
Authors: Miara Lincoln , Yoon Kyung Joong , Topping Stephen G. , Saraf Lax , Pal Uday , Gopalan Srikanth
Published: October 2010

Patterned cathodes of calcium-doped lanthanum manganite (LCM) were fabricated on polycrystalline yttria-stabilized zirconia (YSZ) substrates by RF magnetron sputtering and photolithographic techniques. Samples were generated with a constant electrode/electrolyte contact area but different three phase boundary (TPB) lengths (lTPB's). Electrochemical impedance spectroscopy (EIS) was performed in the oxygen partial pressure (pO2) and temperature range of 10-3 atm to 1.00 atm and 600-800{degree sign}C respectively. The area specific polarization resistance, Rp, was found to scale linearly with the inverse of lTPB, suggesting that the TPB is the active region for oxygen reduction. The resistivity decreased with increased temperature and pO2 and showed an activation energy of 1.17+/-0.03 eV.
Investigation of Proton Transport in the Catalyst Layer of PEM Fuel Cells by Electrochemical Impedance Spectroscopy
Authors: Cimenti Massimiliano , Bessarabov Dmitri , Tam Mickey , Stumper Jürgen
Published: October 2010

The proton conductivity of the catalyst layer is an essential parameter for the design and optimization of PEM fuel cells cathodes. Few methods have been proposed to measure this quantity. In this study we tested two methods based on electrochemical impedance spectroscopy (EIS) measurements performed in H2/N2 and in H2/O2, respectively. The EIS H2/N2 method allows the quantification of the CL proton resistance at equilibrium, and in principle could be used to obtain catalyst layer microstructural information. The EIS H2/O2 method allows the quantification of both ohmic and CL proton resistances under load. According to our results, the EIS H2/N2 method is preferable because it is faster to perform, the data analysis is simpler, and provides the CL resistance at equilibrium.
Model-Based Deconvolution of Potential Losses in a PEM Fuel Cell
Authors: Baghalha Morteza , Stumper Jürgen , Eikerling Michael
Published: October 2010

Deconvolution of potential losses or voltage loss breakdown (VLB) is a method to extract individual component losses, e.g., due to sluggish kinetics, reactant diffusion or charge transport, from measurements of the total potential loss incurred under operation of a polymer electrolyte fuel cell. For efficient fuel cell design and diagnostics, it is desirable to be able to identify the origin of potential losses. The challenge involved in this task is that individual losses can hardly be separated since the underlying physical phenomena are highly interdependent. We propose a two-step deconvolution, which is based on a physical performance model, to calculate the 3 conventional potential losses, including kinetics, ohmic, and mass-transport losses. For medium to highly degraded membrane electrode assemblies (MEA) caused by carbon corrosion, the model-based deconvolution method shows a considerable increase in the potential loss due to reduced oxygen transport, even at low current densities.
The Impact of sub ppm Carbon Monoxide and ppm Level CO/Toluene and Methylcyclohexane/CO Mixtures on PEMFC Performance and Durability
Authors: Angelo Michael , Bethune Keith , Rocheleau Richard
Published: October 2010

This work studied the effects that exposure to the hydrogen fuel impurities: carbon monoxide (CO), toluene and methylcyclohexane (MeCH) had on the performance and durability of GORE{trade mark, serif} PRIMEA® MESGA (A510.1/M710.18/C510.4) membrane electrode assemblies (MEAs) used in hydrogen proton exchange membrane fuel cells (PEMFCs). MEAs used in this work had anode platinum catalyst loadings of 0.1 mg Pt cm-2 and were subjected to both single impurities and impurity mixtures. Gas chromatography was used to study the magnitude of conversion for CO to carbon dioxide (CO2) and toluene to MeCH.
The Impact of SO2 on the Degradation of MEA Components in PEMFCs
Authors: Dorn Susanne , Zhai Yunfeng , Rocheleau Richard
Published: October 2010

The impact of low level concentrations of sulfur dioxide (SO2) and SO2 recovery methods on the degradation of membrane electrode assembly (MEA) components of a polymer electrolyte membrane fuel cell (PEMFC) was studied. MEAs were exposed to 2ppm SO2 for various exposure times at constant current density of 0.6 A/cm2 and a cell temperature of 80oC. Severe performance degradation was observed due to SO2 exposure and cell performance only partially recovered. Ion Chromatography (IC) analysis of the fuel cell effluent water revealed increased fluorine emission due to the presence of SO2. Scanning Electron Microscopy (SEM) of MEA cross sections confirmed a drastic decrease in membrane thickness after exposure to SO2. Transmission Electron Microscopy (TEM) of catalyst sections showed no distinct impact on platinum agglomeration due to SO2 exposure but did confirm an increase in platinum agglomeration due to the application of a cyclic voltammetry recovery method.
Electrodeposited Pt-Ir Thin Films as DMFC Anode Materials
Authors: El Sawy Ehab N. , Birss V. I.
Published: October 2010

Pt-Ir alloys have been reported previously to be very good catalysts towards the methanol oxidation reaction (MOR), although the composition of these films was not known with certainty. In the present work, thin Pt-Ir films of varying, but controlled, composition were fabricated using electrodeposition, with a charge efficiency of close to 100%. X-ray photoelectron spectroscopy (XPS) analysis showed that the film composition is fully homogeneous with depth into the film and that it matches very closely with the metal molar ratio in the deposition solution. The Pt-Ir film composition with the highest MOR activity was found to have a 2:1 Pt:Ir mass ratio and 1:1 surface composition ratio, based on measurements of the underpotentially deposited adsorbed hydrogen charge.
Recent Progress in Anode Materials for Solid Oxide Fuel Cells
Authors: Li Qin , Thangadurai Venkataraman
Published: October 2010

In this paper, we report our recent progress in the development of anode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). Mo-doped Ce1-xMoxO2+δ (x = 0.05, 0.07, 0.1, 0.13) (CMO), Mo + RE-co-doped Ce0.9-xRExMo0.1O2.1-0.5x (x = 0.2, 0.3) (RE = Y, Sm, Gd) (CRMO) and Nd2WO6-type Sm2-xAxM1-yByO6-δ (A = Ca, Sr; M = Mo, W; B = Ce, Ni) have been investigated in our laboratory. For CMO and CRMO, the formation of fluorite-like structure was confirmed by powder X-ray diffraction (PXRD) and the change in the lattice constant was found to be consistent with the Shannon ionic radius trend. CRMO samples treated under dry H2 at elevated temperatures were found to retain the original fluorite structure while CMO showed presence of Mo in the PXRD. Sm2-xAxMoO6-δ (A = Ca, Sr) after heating under 97% H2 +3% H2O up to 850 oC changed from Nd2WO6-type structure into Sm2MoO5 due to the reduction of MoVI that was confirmed by PXRD.
Carbon and Sulfur Poisoning in SOFC Anodes: Ni0.7Co0.3-YSZ Performance with Hydrocarbons, Alcohols and Biodiesel Fuels Containing H2S
Authors: O'Brien Julie S. , Giorgi Javier B.
Published: October 2010

The poisoning behavior of hydrogen sulfide at the concentrations presented has the effect of lessening the amount of coke formation experienced at the anode site of the active Ni0.7Co0.3-YSZ cermet. Although the effect of coke formation becomes more dramatic and detrimental to the cell as the length of the hydrocarbon chain increases, the ability of the hydrogen sulfide to protect the anode against coke formation also increases, producing a smaller reduction in exchange current density with increasing hydrocarbon length. For the case of biodiesel fuel, at a concentration of 5 % hydrogen sulfide, the exchange current density is higher and the cell survives much longer than with pure biodiesel fuel. Hydrogen sulfide also has the effect of increasing the lifetime of the cell to be several times that of the pure hydrocarbon fuel.
Developing an Electrochemical Method to Assess SOFC Anode Losses during H2S Poisoning under Polarization
Authors: Paulson Scott C. , Sponiar Matthew , Birss V. I.
Published: October 2010

A 3-electrode electrochemical method has been used to quantitatively assess the influence of ppm levels of H2S on the hydrogen oxidation performance of Ni-based solid oxide fuel cell (SOFC) anodes as a function of applied current over a reasonable time frame. When performed under near identical polarization history due to non-steady-state anode behavior, this work shows that low currents (moderate overpotentials) do not influence the magnitude of S poisoning of Ni-based anodes. Furthermore, activation by polarization or infiltration of the Ni-YSZ anode with ceria does not seem offer any dramatic improvement in sulfur poisoning resistance at 764 oC, and relative recovery after H2S exposure is found to be worse in the case of ceria.
Impacts of Ru Dissolution and Crossover on Polymer Electrolyte Membrane Fuel Cell Performance and Anode Functionality
Authors: Cheng Tommy , Colbow Vesna , Wessel Silvia , Chuy Carmen , He Ping
Published: October 2010

Carbon-supported PtRu catalysts are commonly used as anode catalysts in polymer electrolyte membrane fuel cells (PEMFCs) to provide CO tolerance for reformate fuel applications. However, Ru dissolution and subsequent crossover from the anode to the cathode have been identified as critical durability issues. In this investigation, half-cell electrochemical studies were carried out to characterize the changes and impacts imposed by Ru contamination on the cathode. In addition, an anode accelerated stress test (AST) was employed in a fuel cell to simulate potential spikes that occur during fuel cell start-ups and shutdowns to induce Ru dissolution and crossover. The electrochemical experiments showed that the oxygen reduction reaction (ORR) activity and the changes in cyclic voltammetry (CV) characteristics correlated well with the amount of Ru deposited on the cathode. From the single-cell AST results, it was evident that both the performance and CO tolerance were severely impacted by Ru dissolution and crossover.
Prospective of Pd/MOx as Alternative Pt Anode Catalyst for Polymer Electrolyte Fuel Cell
Authors: Muhamad Ernee Noryana , Takeguchi Tatsuya , Wang Guo-Xiong , Yamanaka Toshiro , Ueda Wataru
Published: October 2010

The performances of anode Pd catalysts modified with metal oxides in CO-contaminated H2 were investigated for polymer electrolyte fuel cell (PEFC). The catalysts were prepared by facile impregnation method and characterized by X-ray diffraction (XRD), scanning transmission electron microscope (STEM) and CO-stripping voltammetry. Comparison of both modified Pd anode with pure Pd/C and state-of-the-art Pt/C shows an improvement in the cell performance when 500 ppm CO/H2 mixture is fed. The improvement was due to much smaller Pd particle size, which significantly increases the electrochemical surface area (ECSA). In principle, carbon-supported Pd modified with metal oxides catalyst has shown a possibility to replace the used of Pt as anode electrode for PEFC.
3D Multiphase Modeling of PEMFC with Uneven Compression of GDL
Authors: Qi Liang , Jiao Kui , Pereira Aaron , Li Xianguo
Published: October 2010

Mass transport in the proton exchange membrane fuel cell is heavily impacted by deformation of the gas diffusion layer (GDL) due to the resultant changes of porosity and permeability. The effects of deformation, due to uneven compression, on water transport are investigated by using finite element analysis (FEA) and three-dimensional multi-component, multi-phase models. Numerical results indicate that clamping forces have a significant influence on water distribution in the membrane electrode assembly (MEA). Analysis of both membrane water content and liquid water content in the GDL and catalyst layer (CL) show that a higher clamping force helps retain water in the membrane on the anode side but leads to worse water flooding on the cathode side.
Carbon-Supported Pt-Pd Alloy as a Methanol-Tolerant-Oxygen-Reduction Electro-Catalyst for DMFCs
Authors: Nishanth Karimbintherikkal , Sridhar Parthasarathi , Pitchumani Sethuraman , Shukla Ashok
Published: October 2010

High-performance methanol-tolerant Pt-Pd alloy on carbon with varying Pt:Pd atomic ratio of 1:1, 2:1 and 3:1 was prepared by a facile wet-chemical method and characterized by XRD, FESEM and EDX techniques. The optimum atomic weight ratio of Pt to Pd in the carbon-supported alloy catalyst as established by linear-sweep voltammetry (LSV) and cell-polarization studies is determined to be 2:1. A direct methanol fuel cell (DMFC) comprising a carbon-supported Pt-Pd(2:1) alloy (1mgPt /cm2) as the cathode catalyst delivers a peak-power density of 115 mW/cm2 at 70°C in contrast with the peak-power density value of 60mW/cm2 delivered by the DMFC with carbon-supported Pt catalyst operating under similar conditions.
In Situ Observation of CO Oxidation by Anode PtRu/C Catalysts for Polymer Electrolyte Fuel Cells
Authors: Yamanaka Toshiro , Takeguchi Tatsuya , Wang Guo-Xiong , Muhamad Ernee Noryana , Ueda Wataru
Published: October 2010

An anode catalyst for a polymer electrolyte fuel cell should be CO-tolerant, i.e., it should have the function of hydrogen oxidation in the presence of CO, since hydrogen fuel gas generated by the steam reforming process of natural gas contains CO. Our recent results showed that highly dispersed PtRu/C (HD) with small metal particles has much higher CO tolerance than that of poorly dispersed PtRu/C (LD) with large metal particles. CO tolerance is often discussed in connection with activity for CO oxidation, but the mechanism of CO oxidation is not clear. To study the mechanism for CO tolerance and CO oxidation, we have developed an apparatus for variable temperature in-situ FT-IR measurements of CO oxidation. It is expected that electro oxidation and thermal CO oxidation of CO can be distinguished from temperature- and potential-dependence CO2 formation and that these dependence will provide some information on the mechanism of CO tolerance of catalysts.
Impedance Analysis of PdCo as Cathode for PEM Fuel Cells
Authors: Vázquez-Huerta Gerardo , Martínez-Casillas Diana C. , Solorza-Feria Omar
Published: October 2010

In this work the oxygen reduction reaction (ORR) on PdCo particles (~ 11 nm) supported in carbon Vulcan XC-72 is analyzed. In 0.5 M H2SO4/O2 the impedance spectra showed one or two time constants, the first time constant was associated to the reduction of O2 to H2O, while the second, to the reduction from H2O2 to H2O. By using electric circuits, the kinetics parameters of ORR were obtained. The values of charge transfer resistance Rct1 obtained from the impedance spectra were used to determine the kinetic parameters (b, α and i0) of ORR. The impedance spectra of PEMFC fed with H2/air and H2/O2 allows determining the values of Rc; with these, the values of b, α, and i0 were calculated. The values of i0, are related to the kinetics of ORR on PdCo/C, the highest value of i0 belongs to the PEMFC fed with H2/O2.
Fabrication of Hydrophobic Coating on GDL with Silicone Based Materials
Authors: Wang Yongxin , Al Shakhshir Saher , Li Xianguo
Published: October 2010

In this study, a hydrophobic coating is fabricated on gas distribution layer (GDL) with silica particle/polydimethylsiloxane (PDMS). For the coated GDL surface, the measured water contact angle is about 162° and sliding angle about 5°. The pore size of the coated GDL is about 7.1 μm, and shows low energy resistance to the gas transport. Performance tests of the polymer electrolyte membrane fuel cells (PEMFCs) indicate that PEMFCs made of such GDLs offer the better performance than conventional PEMFCs.
Improving CO Tolerance of Pt2Ru3/C Catalyst by the Addition of Tin Oxide
Authors: Wang Guo-Xiong , Takeguchi Tatsuya , Yamanaka Toshiro , Muhamad Ernee Noryana , Ueda Wataru
Published: October 2010

SnOx-modified Pt2Ru3/C catalysts were post-treated in different atmospheres at various temperatures to improve the catalytic activity for H2/CO electro-oxidation. The structures of the Pt2Ru3/C and SnOx/Pt2Ru3/C catalysts were characterized by X-ray diffraction. Electrochemical activities were evaluated by CO stripping voltammetry and single cell test. The SnOx/Pt2Ru3/C catalysts had a lower onset potential for CO electro-oxidation and greater cell voltage than the Pt2Ru3/C catalyst under high CO concentrations. The SnOx/Pt2Ru3/C catalyst treated in 5 % H2/Ar at 150oC exhibited the greatest CO tolerance due to that the post-treatment caused the conversion of SnO2 to SnOx (1{less than or equal to} x {less than or equal to}2) without destroying PtRu alloy structure.
Electrochemical Impedance Spectroscopy Analysis on SO2 Contamination in PEMFCs
Authors: Zhai Yunfeng , Bethune Keith , Dorn Susanne , Bender Guido , Rocheleau Richard
Published: October 2010

Electrochemical impedance spectroscopy (EIS) was applied to analyze the effects of 2 ppm SO2 on the electrochemical reactions in PEMFCs cathode during the two-stage performance degradation. An equivalent electrical circuit model (ECM) was used to fit the resistances of the fuel cell reactions. The extracted parameters of the oxygen reduction reaction (ORR) suggested that during the first poisoning stage, the SO2 adsorption increased the charge transfer resistance of the ORR and caused the initial degradation in cell performance. During the second poisoning stage, SO2 adsorption might assist in shifting the ORR from the "direct four electron pathway" to the "series two electron pathway", which may have resulted in the subsequent degradation in cell performance.
Simulation of Three-Dimensional Solid-by-Solid Model and Application to Electrochemical Engineering
Authors: Kaneko Yutaka , Hiwatari Yasuaki , Ohara Katsuhiko , Asa Fujio
Published: October 2010

A multi-scale kinetic Monte Carlo method has been developed for the molecular simulation of electrodeposition. The basic system is the solid-by-solid model which is a new model for crystal growth with vacancy formation. This model is extended to include the solution and the diffusion layer to take into account the concentration overpotential. The migration of ions in solution is simulated by the coarse-grained random walk. Since the time and length scales in the diffusion layer are largely different from those of the atomic events on the electrode surface, a multi-scale simulation method has been used for the diffusion layer. We have performed the simulation of copper electrodeposition and confirmed that the shape evolution of the surface can be simulated with the formation of the concentration gradient in the diffusion layer.
Tailoring Copper Island Density for Copper Plating on a RuTa Substrate
Authors: Nagar Magi , Vereecken Philippe M. , Radisic Aleksandar , Strubbe Katrien
Published: October 2010

The electrochemical nucleation and growth of copper on a ruthenium-tantalum (RuTa) alloy has been studied using galvanostatic methods. The experimental results show that the island density is highly dependent on the bath composition and deposition parameters. High island density was achieved with higher applied current, addition of suppressor and low copper concentration in the plating bath.
New Proposal for the Interfacial Design toward the Establishment of Electrochemical Device Engineering
Authors: Osaka Tetsuya , Nakanishi Takuya
Published: October 2010

This paper describes an overview of our research with the title of Establishment of Electrochemical Device Engineering. The goal of this work is to develop systematic methodologies for the creation of advanced materials and devices based on the design of the interface, which is derived from our study of the practical application of Electrochemical Nanotechnology. We introduce three-, two-, and zero-dimensional viewpoints to the design of the interface between electrode and electrolyte based on electrochemical nanotechnology. In this manuscript, two-dimensional design is explained first and then three- and zero-dimensional topics are mentioned.
One-Dimensional Molecular Junction Arrays Fabricated Using Anodic Aluminum Oxide Templates
Authors: Song Youngsik , Jun Fang , Chen Zhi D.
Published: October 2010

We fabricated molecular junction arrays using one-dimensional anodic aluminum oxide templates and measured the corresponding current-voltage characteristics. A one dimensional nanopore array was fabricated from an aluminum layer that was sandwiched between two silicon dioxide layers on a silicon substrate. Depending upon the geometry of molecules and contact, the current-voltage characteristics of self-assembled molecular junction arrays showed symmetric or asymmetric charge transport behavior.
Pulse Electrolysis in the Electro-Oxidation on the Ti/SnO2-Sb2O5 Anode for Wastewater Treatment
Authors: Ni Qing , Kirk Donald W. , Thorpe Steven J.
Published: October 2010

Electro-oxidation is a potentially efficient method to remove organic compounds commonly found in municipal wastewater. Compared to the conventional treatment by microbial digestion, electro-oxidation can offer significant saving in capital equipment, land footprint and treatment time. However, one of the biggest challenges facing this technology is to reduce the energy consumption associated with treatment. This work investigated the possible use of square-wave current pulsing as an electrolysis technique to improve the current efficiency. The experiments evaluated the efficiencies of electro-oxidation in simulated and actual wastewater. Two electrolysis modes, constant current and pulsing, were compared. The results indicate that the overall efficiency was dependent only on the average current, and there was no significant difference between pulsing and steady state electrolysis. This result suggests further study of the mass-transport characteristics of the organic compounds at the electrode-electrolyte interface.
Fundamental Thermodynamic Modifications in Wagner's Equation in Solid State Electrochemistry
Authors: Miyashita Tomofumi
Published: October 2010

The use of samarium-doped ceria (SDC) electrolytes in solid oxide fuel cells (SOFCs) lowers the open circuit voltage (OCV) below the Nernst voltage (Vth). The OCV is calculated with Wagner's equation, which is included in the Nernst-Planck equation. This paper considers the fundamental basis of the separation of the Boltzmann distribution. A constant voltage loss without leakage currents has been found to arise from a mixed ionic and electronic conducting (MIEC) dense anode. Only carrier species with sufficient energy to overcome the activation energy can contribute to current conduction, which is shown by incorporating a different constant into the definitions of chemical potential and electrical potential. This difference explains the results obtained using dense MIEC anodes. This topic is not an isolated or minor topic, but is of vital importance to the future of electrochemical engineering. Several future technological applications of these theoretical considerations are also introduced.
Structural and Protecting Properties of Functional Organic Coatings on Copper
Authors: Petrović Željka , Metikoš-Huković Mirjana , Omanovic Sasha , Leskovac Mirela
Published: October 2010

The paper presents a new approach to the enhancement of structural and barrier properties of thioaromatic self-assembled films on polycrystalline copper. Self-assembled thioaromatic films were modified by potentiodynamic cycling in ethanolic solutions containing milimolar quantities of 1-dodecanethiol. Results obtained using goniometry and polarization modulation infrared reflection absorption spectroscopy demonstrated an improvement in films' structural properties, including higher surface packing density, order and hydrophobicity of electrochemically modified over unmodified thioaromatic films, due to the repair of film defects/pores and exchange. Impedance spectroscopy results showed that the electrochemically modified thioaromatic films offer high corrosion protection in aqueous saline solution, in comparison to spontaneously formed thioaromatic films.