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Full-Text Articles in Engineering
Water Transport In Polymer Electrolyte Membrane Electrolyzers Used To Recycle Anhydrous Hcl: I. Characterization Of Diffusion And Electro-Osmotic Drag, Sathya Motupally, Aaron J. Becker, John W. Weidner
Water Transport In Polymer Electrolyte Membrane Electrolyzers Used To Recycle Anhydrous Hcl: I. Characterization Of Diffusion And Electro-Osmotic Drag, Sathya Motupally, Aaron J. Becker, John W. Weidner
Faculty Publications
In this paper, diffusion and electro-osmotic drag of water across Nafion® membranes in the presence of HCl are characterized. For all the measurements, one side of the Nafion membrane was in contact with liquid water and the other side with gaseous anhydrous HCl. To characterize diffusion of water, the open-circuit flux of water across a catalyst-coated Nafion 115 membrane was measured as a function of HCl flow rate and temperature at a constant cell pressure of 1 atm. Due to the nature of varying driving force for diffusion as a function of HCl flow rate, the experimental data was analyzed …
Using Sputter Deposition To Increase Co Tolerance In A Proton-Exchange Membrane Fuel Cell, Andrew T. Haug, Ralph E. White, John W. Weidner, Wayne Huang, Steven Shi, Narender Rana, Stephan Grunow, Timothy C. Stoner, Alain E. Kaloyeros
Using Sputter Deposition To Increase Co Tolerance In A Proton-Exchange Membrane Fuel Cell, Andrew T. Haug, Ralph E. White, John W. Weidner, Wayne Huang, Steven Shi, Narender Rana, Stephan Grunow, Timothy C. Stoner, Alain E. Kaloyeros
Faculty Publications
Placing a layer of Ru atop a Pt anode increases the carbon monoxide tolerance of proton-exchange membrane fuel cells when oxygen is added to the fuel stream. Sputter-deposited Ru filter anodes composed of a single Ru layer and three Ru layers separated by Nafion-carbon ink, respectively, were compared to Pt, Pt:Ru alloy, and an ink-based Ru filter anodes. The amount of Pt in each anode was 0.15 mg/cm2 and the amount of Ru in each Ru-containing anode was 0.080 mg/cm2. For an anode feed consisting of hydrogen, 200 ppm CO, and 2% O2 (in the form …
Study Of Sn-Coated Graphite As Anode Material For Secondary Lithium-Ion Batteries, Basker Veeraraghavan, Anand Durairajan, Bala Haran, Branko N. Popov, Ronald Guidotti
Study Of Sn-Coated Graphite As Anode Material For Secondary Lithium-Ion Batteries, Basker Veeraraghavan, Anand Durairajan, Bala Haran, Branko N. Popov, Ronald Guidotti
Faculty Publications
Tin-graphite composites have been developed as an alternate anode material for Li-ion batteries using an autocatalytic deposition technique. The specific discharge capacity, coulombic efficiency, rate capability behavior, and cycle life of Sn-C composites has been studied using a variety of electrochemical methods. The amount of tin loading and the heating temperature have a significant effect on the composite performance. The synthesis conditions and Sn loading on graphite have been optimized to obtain the maximum reversible capacity for the composite electrode. Heating the composite converts it from amorphous to crystalline form. Apart from higher capacity, Sn-graphite composites possesses higher coulombic efficiency, …
Modeling The Effects Of Ion Association On Alternating Current Impedance Of Solid Polymer Electrolytes, Changqing Lin, Ralph E. White, Harry J. Ploehn
Modeling The Effects Of Ion Association On Alternating Current Impedance Of Solid Polymer Electrolytes, Changqing Lin, Ralph E. White, Harry J. Ploehn
Faculty Publications
This work presents a rigorous continuum model describing the transport of ions and associated ion pairs in solid polymer electrolytes subjected to small amplitude alternating current (ac) excitation. The model treats ion association as a reversible reaction among ions and ion pairs. Dimensionless governing equations are developed from component mass balances, flux equations based on dilute solution theory, and the Poisson equation. Assuming reversible electrode reactions and electroneutrality, the model equations have an analytical solution. Further simplifications are possible in limiting cases (weak and strong association, zero and infinite frequency excitation), giving expressions consistent with previously published models. We use …
Electrochemical Filtering Of Co From Fuel-Cell Reformate, Balasubramanian Lakshmanan, Wayne Huang, John W. Weidner
Electrochemical Filtering Of Co From Fuel-Cell Reformate, Balasubramanian Lakshmanan, Wayne Huang, John W. Weidner
Faculty Publications
A proton exchange membrane fuel cell was used as a flow reactor for continuous preferential oxidation of CO over H2 from 1.0% CO in H2 under pulse-potential control. By varying the pulse profile ~e.g., on-time, off-time, pulse potential! the CO and H2 oxidation currents were varied independently. The improvement in faradaic selectivity between CO and H2 oxidation results from the promotion of CO adsorption during the off ~i.e., open-circuit! portion of the pulse. Therefore, during the on portion CO oxidation was preferred while the surface was covered with CO.
Increasing Proton Exchange Membrane Fuel Cell Catalyst Effectiveness Through Sputter Deposition, Andrew T. Haug, Ralph E. White, John W. Weidner, Wayne Huang, Steven Shi, Timothy Stoner, Narender Rana
Increasing Proton Exchange Membrane Fuel Cell Catalyst Effectiveness Through Sputter Deposition, Andrew T. Haug, Ralph E. White, John W. Weidner, Wayne Huang, Steven Shi, Timothy Stoner, Narender Rana
Faculty Publications
Sputter deposition has been investigated as a tool for manufacturing proton-exchange membrane fuel cell (PEMFC) electrodes with improved performance and catalyst utilization vs. ink-based electrodes. Sputter-depositing a single layer of Pt on the gas diffusion layer provided better performance (0.28 A/cm2 at 0.6 V) than sputtering the Pt directly onto a Nafion membrane (0.065 A/cm2 at 0.6 V) and equaled the performance of the baseline for an equivalent Pt loading. Sputter-depositing alternating layers of Pt and Nafion-carbon ink (NCI) onto the membrane did not increase the performance over the baseline as measured in amperes per centimeter squared due …
Estimation Of Diffusion Coefficient Of Lithium In Carbon Using Ac Impedance Technique, Qingzhi Guo, Venkat R. Subramanian, John W. Weidner, Ralph E. White
Estimation Of Diffusion Coefficient Of Lithium In Carbon Using Ac Impedance Technique, Qingzhi Guo, Venkat R. Subramanian, John W. Weidner, Ralph E. White
Faculty Publications
The validity of estimating the solid phase diffusion coefficient, Ds, of a lithium intercalation electrode from impedance measurement by a modified electrochemical impedance spectroscopy (EIS) method is studied. A macroscopic porous electrode model and concentrated electrolyte theory are used to simulate the synthetic impedance data. The modified EIS method is applied for estimating Ds. The influence of parameters such as the exchange current density, radius of active material particle, solid phase conductivity, porosity, volume fraction of inert material, and thickness of the porous carbon intercalation electrode, the solution phase diffusion coefficient, and transference number, on the …
Development Of A Novel Co Tolerant Proton Exchange Membrane Fuel Cell Anode, Andrew T. Haug, Ralph E. White, John W. Weidner, Wayne Huang
Development Of A Novel Co Tolerant Proton Exchange Membrane Fuel Cell Anode, Andrew T. Haug, Ralph E. White, John W. Weidner, Wayne Huang
Faculty Publications
Typically Pt is alloyed with metals such as Ru, Sn, or Mo to provide a more CO-tolerant, high-performance proton exchange membrane fuel cell (PEMFC) anode. In this work, a layer of carbon-supported Ru is placed between the Pt catalyst and the anode flow field to form a filter. When oxygen is added to the fuel stream, it was predicted that the slow H2 kinetics of Ru in this filter would become an advantage compared to Pt and Pt:Ru alloy anodes, allowing a greater percentage of O2 to oxidize adsorbed CO to CO2. With an anode feed …
Studies On Capacity Fade Of Spinel-Based Li-Ion Batteries, Ramadass Premanand, Anand Durairajan, Bala Haran, Ralph E. White, Branko N. Popov
Studies On Capacity Fade Of Spinel-Based Li-Ion Batteries, Ramadass Premanand, Anand Durairajan, Bala Haran, Ralph E. White, Branko N. Popov
Faculty Publications
The performance of Cell-Batt® Li-ion cells using nonstoichiometric spinel as the positive electrode material has been studied at different charging rates. The capacity of the cell was optimized based on varying the charging current and the end potential. Subsequent to this, the capacity fade of these batteries was studied at different charge currents. During cycling, cells were opened at intermittent cycles and extensive material and electrochemical characterization was done on the active material at both electrodes. For all charge currents, the resistance of both the electrodes does not vary significantly with cycling. This result is in contrast with cells …
Modeling The Effects Of Electrode Composition And Pore Structure On The Performance Of Electrochemical Capacitors, Changqing Lin, Branko N. Popov, Harry J. Ploehn
Modeling The Effects Of Electrode Composition And Pore Structure On The Performance Of Electrochemical Capacitors, Changqing Lin, Branko N. Popov, Harry J. Ploehn
Faculty Publications
This work presents a mathematical model for charge/discharge of electrochemical capacitors that explicitly accounts for particle-packing effects in a composite electrochemical capacitor consisting of hydrous RuO2 nanoparticles dispersed within porous activated carbon. The model is also used to investigate the effect of nonuniform distributions of salt in the electrolyte phase of the electrode in the context of dilute solution theory. We use the model to compare the performance of capacitors with electrodes made from different activated carbons and to investigate the effects of varying carbon content and discharge current density. Even at low discharge current density, concentration polarization in …
Anodic Behavior Of Ti In Koh Solutions: Ellipsometric And Micro-Raman Spectroscopy Studies, A. Prusi, Lj. Arsov, Bala Haran, Branko N. Popov
Anodic Behavior Of Ti In Koh Solutions: Ellipsometric And Micro-Raman Spectroscopy Studies, A. Prusi, Lj. Arsov, Bala Haran, Branko N. Popov
Faculty Publications
Anodic formation of oxide films on titanium surfaces, in various concentrations of aqueous KOH solutions, have been studied using ellipsometry and micro-Raman spectroscopy. By in situ ellipsometric measurements the coefficient of film thickness growth and indexes of refraction of anodic oxide films have been determined. The voltage at which the oxide film breaks down is strongly dependent on the KOH concentration. Further, the solution concentration strongly influences the potential at which the oxide film is transformed from the amorphous state to crystalline form. Using micro-Raman spectroscopy four crystalline forms of titanium oxides, namely, anatase, brookite, corundum, and rutile, have been …
Modeling The Effects Of Electrode Composition And Pore Structure On The Performance Of Electrochemical Capacitors, Changqing Lin, Branko N. Popov, Harry J. Ploehn
Modeling The Effects Of Electrode Composition And Pore Structure On The Performance Of Electrochemical Capacitors, Changqing Lin, Branko N. Popov, Harry J. Ploehn
Faculty Publications
This work presents a mathematical model for charge/discharge of electrochemical capacitors that explicitly accounts for particle-packing effects in a composite electrochemical capacitor consisting of hydrous RuO2 nanoparticles dispersed within porous activated carbon. The model is also used to investigate the effect of nonuniform distributions of salt in the electrolyte phase of the electrode in the context of dilute solution theory. We use the model to compare the performance of capacitors with electrodes made from different activated carbons and to investigate the effects of varying carbon content and discharge current density. Even at low discharge current density, concentration polarization in …