Clay Crystallization Mechanisms Probed by Optical Spectroscopy. JESSICA TYRUS (Benedictine University Lisle, IL 60532) KATHLEEN A. CARRADO (Argonne National Laboratory, Argonne, IL, 60439)

Synthetic hectorite clays can be used as heterogeneous catalyst supports and in various other technological applications, thereby placing an importance upon obtaining a knowledge and understanding of the mechanism of clay formation in order to determine an efficient and effective synthetic process. Previous studies focused on the formation of "silica-hectorites," and a silica-clay crystallization mechanism has been proposed. Currently, the mechanism for the complimentary suite of materials referred to as "silane-hectorites" is being studied, and this research focused on using rhodamine 6g perchlorate, a cationic dye, as an optical probe. Successful synthesis of TEOS-hectorite monitored at various time intervals, as well as ion-exchange of silane-hectorite and laponite, with this probe was monitored by X-ray diffraction (XRD), thermogravimetric analysis (TGA), and fluorescence spectroscopy. Data obtained by XRD for ion-exchanges involving each of two concentrations of the dye and both TEOS-hectorite and laponite-RD provided a baseline for the d-spacing of the clays upon full crystallization, as this d-spacing was found to fall between 13 and 15 Å. Data obtained by XRD for the in situ crystallization of TEOS-hectorite at various time intervals allowed for the monitoring of the crystallization of the clay and dye, with clay crystallization beginning after 12 hours. The results obtained via TGA show significant weight losses in the 300-450 °C range; these will have to be scrutinized for weight loss from organic dye decomposition versus Mg(OH)₂ precursor decomposition due to incomplete clay crystallization. Additional data obtained via fluorescence spectroscopy allowed for the determination of the excitation and emission peaks for the 16-hour crystallization of the clay with 1.0 x 10^-5 M dye at 531 nm and 557 nm, respectively. Excitation and emission peaks were not obtained for crystallizations occurring after other periods of time, perhaps due to an insufficient concentration of dye incorporated into the clay.

Computational Fluid Dynamics and Electrochemical Modeling of a Sulfur Trioxide Electrolysis Cell for use in the Westinghouse Hybrid Sulfur Cycle. KATHERINE HOHNHOLT (Massachusetts Institute of Technology Cambridge, MA 02141) DEBORAH J MYERS (Argonne National Laboratory, Argonne, IL, 60439)

Recently hydrogen has become an exciting new alternative for fueling automotive transportation. Hydrogen, however, has to be produced. One proposed cycle is the Westinghouse Hybrid Sulfur Cycle, which uses the electrolysis of water and sulfur dioxide to produce sulfuric acid and hydrogen. Subsequently, the sulfuric acid is thermally decomposed to sulfur trioxide. Additionally, the sulfur dioxide is regenerated by thermal decomposition of sulfur trioxide. The cycle is promising because it requires less electrical energy then pure water electrolysis. A major disadvantage to this cycle, however, is the extremely high temperatures (>1000 C) required for sulfur trioxide decomposition. An additional electrolysis cell designed to decompose sulfur trioxide at lower temperatures (500 C-600 C) is one proposed solution to this problem. In order to better understand the potential of this alternative, an electrochemical and fluid dynamics model was developed using the commercial code - Star-CD. A previous model developed at Argonne National Laboratory used to model water electrolysis was updated to change the thermodynamic and fluid properties of the new cell. Additional adjustments to the cell model were made in order to improve the calculation of three key variables: the exchange current, limiting current, and diffusivity. In order to determine the feasibility of the temperature range chosen, the thermodynamic stability of the electrolyte was examined. The stability calculations suggested that the electrolyte would be more stable at higher temperatures. The model was run at varying temperatures and product concentrations to examine the effects on cell properties and production. Increasing temperature and decreasing sulfur dioxide inlet mass fraction both increased current density and thus production through the cell. However, they also decreased the voltage efficiency of the cell and increased temperature gradients.

Exploring the solution phase conformations of a cyclic porphryin hexamer by combining molecular simulations with high-angle x-ray scattering data. KRISTY MARDIS (Chicago State University Chicago, IL 60628) KRISTY MARDIS (Argonne National Laboratory, Argonne, IL, 60439)

The determination of the structure of macromolecular complexes is a crucial step in the design of supramolecular assemblies. The usage of such complexes often depends on their ability to maintain a particular conformation in solution. Unfortunately, the common techniques of solidstate X-ray diffraction and solution phase NMR are often inadequate for supramolecular assembly structural determination. High-angle X-ray scattering provides a complementary technique for solution phase structural determination. When used in conjunction with molecular simulations, high-angle X-ray scattering allows for the testing of structural models and the measurement of solution state configurational dispersions. The current work focuses on performing molecular simulations on a cyclic diphenylethyne-linked porphyrin hexamer. Such porphyrin based structures are important in photochemistry and energy transfer applications. Constant pressure temperature simulations using the Charmm 22 force field in explicit solvent (toluene) were able to accurately reproduce the experimental scattering data. The conformations present in the simulation indicate that the prophyrin subunits undergo a great deal of twisting motion-some becoming nearly parallel with the plane of the ring. These results provide new insight into the structural flexibility of this complex in solution and will allow a structural basis for the understanding of the photophysical and host-guest possibilities of the hexameric porphyrin assembly in solution. Furthermore, the success of this project as a testcase for the combination of simulation and high-angle x-ray diffraction data for the determination of macromolecular structure supports our plan to engage in additional simulations of cytochrome c ­ porphyrin complexes important as possible energy-transfer devices.

Investigation of Non-Platinum Based Electrocatalysts for Proton Exchange Membrane Fuel Cell Cathodes. MICHAEL AMOLINS (Augustana College Sioux Falls, SD 57197) DR. XIAOPING WANG (Argonne National Laboratory, Argonne, IL, 60439)

The energy crisis has forced the scientific community to investigate possible alternative, renewable energy sources for transportation applications. One such possibility is the proton exchange membrane fuel cell (PEM fuel cell). This fuel cell uses hydrogen gas as fuel and oxygen from the air to produce electricity, which can be used to power a vehicle. Emissions include only water, making it an environmentally friendly process. One of the major issues, however, is that the only PEM fuel cell cathode electrocatalysts currently capable of the most efficient reduction of oxygen to water are platinum-based, making them too expensive for commercial applications. In order to address this cost issue, research has been performed to investigate equally efficient and less expensive non-platinum-based electrocatalyst alternatives. Several transition metal-based bimetallic systems on carbon support have been synthesized using methods of co-precipitation deposition and co-impregnation. The activity for the oxygen reduction reaction (ORR) of a select number of these electrocatalysts has been tested using cyclic voltammetry and rotating disk electrode technique. Some show promise as PEM fuel cell cathodes. Specifically, one bimetallic system has shown ORR potentials as high as 0.85 V, nearly comparing to that of platinum at about 0.95 V. The effect of oxidized carbon support on ORR activity was also studied and showed an increase in electrocatalyst performance at a lower metal loading. These features have given promise to the possible use of bimetallic transition metal electrocatalysts in future PEMFC developments.

Molecular Simulations of a Hexameric Porphyrin Supramolecular Assembly using Langevin Dynamics. TONI SANDERS (Chicago State University Chicago, IL 60628) DR. DAVID TIEDE (Argonne National Laboratory, Argonne, IL, 60439)

There is a need for an accurate method to determine the structure of supramolecular assemblies in solution. X-ray crystallography provides structural information only in the solid phase and NMR cannot distinguish between identical subunits in a common motif in supramolecular assemblies. In contrast, high-angle x-ray diffraction may be an appropriate technique to determine the solution phase conformations of supramolecular structures. To take full advantage of high-angle x-ray diffraction, the experimental scattering patterns need to be combined with scattering data obtained from atomic level molecular models. In this work, we used CHARMM 22 and Langevin dynamics to model a supramolecular complex made up of six porphyrin rings, three containing zinc. When the calculated scattering data from the hexamer model was examined, it was found that simulations with collision frequencies of 20 ps^-1, 15 ps^-1, 10 ps^-1 had similar scattering patterns. However, the calculated scattering pattern displayed a peak around 0.6 Å^-1 that is larger than the one present in the experimental data. This larger peak stems from the structure being too organized and rigid. Collision frequencies of less than or equal to 5 ps^-1 caused the porphyrin hexamer to unphysically pucker or fold. Because the collision frequency was too small, the frictional drag was not enough to maintain equilibrium ensembles and a shift in the scattering pattern compared to experimental data occurred. If the simulation is run longer than 200 ps there is a possibility that the calculated data will better match the experimental data. In any case, the simulations suggest that the hexamer complex is more flexible than had previously been thought.

Olivine Composite Cathode Materials for Improved Lithium Ion Battery Performance. REBECCA WARD (McDaniel College Westminster, MD 21157) JOHN VAUGHEY (Argonne National Laboratory, Argonne, IL, 60439)

Composite cathode materials in lithium ion batteries have become the subject of great research interest recently as safety issues related to LiCoO2 and other layered structures have been discovered. Both the spinel and olivine families have been studied as possible alternatives to the layered cathodes, but these structures present different problems, as spinels have low capacities and cycle poorly at high temperatures, and olivines exhibit extremely low conductivity. Composites of layered-olivine and spinel-olivine structures could stabilize one another thermodynamically and provide the balance between performance and safety necessary for the use of lithium ion batteries in portable electronic devices, particularly the hybrid-electric vehicle. In this study, layered-olivine and spinel-olivine composites were synthesized from precursor salts using three methods: direct reaction, ballmilling and the core-shell synthesis method. X-ray diffraction images and cycling data show that the core-shell method was the most successful in forming the desired products. The electrochemical performance of the cells containing the composite cathodes varied dramatically, but the low overpotential and reasonable capacities of the spinel-olivine composites make them a promising class for the next generation of lithium ion battery cathodes.

Optimization of Synthetic Clay Materials for Advanced Energy Applications: Deep Hydrodesulfurization Activity of Ni/Mo/S Synthetic Clays adn Controlling ORgano-Density of Grafted Synthetic Clays. GREGORY KUZMANICH (University of Illinois at Urbana Champaign Champaign-Urbana, IL 61801) KATHLEEN CARRADO (Argonne National Laboratory, Argonne, IL, 60439)

Contributions towards two projects for the Catalyst Design Group were made developing synthetic clays for two different applications. One project provides supports for hydrodesulfurization (HDS) catalysts. The other is optimizing organo-grafted materials for possible use in specialty polymer-clay nanocomposites or in solar energy applications. Synthetic clays derived from silica sol have been loaded with a Co/Mo/S mixture and examined as a less expensive materials, more efficient catalyst to desulfurize crude oil. The clays were tested with collaborators at Pennsylvania State University (PSU) to measure the conversion of dimethyl dibenzothiophene, and the results indicated that desulfurization was obtained at a rate similar to a current commercial catalyst. The project now is to determine whether a synthetic clay loaded with a Ni/Mo/S mixture would produce conversions equal to or better than commercial catalysts. The synthetic clays have been made from various silica sols or ion-exchanged versions of pre-made clays. These clays were then characterized by x-ray diffraction (XRD) and thermal gravimetric analysis (TGA) to determine their structure and composition, as well as by N ₂ porosimetry to determine adsorption/desorption isotherms, surface areas, and pore volumes. All of the clays produced synthetically were determined to be pure. These clays will be loaded with Ni/Mo/S by Professor Song at PSU and tested for their HDS activity. The second project prepares synthetic clays using alkoxysilanes. The goal of this project is to combine alkoxysilanes and organoalkosysilanes in various mixtures in order to create materials of varying densities of organo groups grafted to the silicate surface. Controlling the spacing between organic groups in this fashion can have effects on affinities for polymer-clay nanocomposite applications. In addition, further derivitization of the organo groups can be utilized for bonding both electron donor and acceptor groups for solar energy applications. The clays synthesized were made by combining various ratios of tetraethoxysilane and phenyltriethoxysilane, and they indicated the formation of silica clay through the use of XRD. The amount of organic material was tested through the use of TGA. The results were promising that organo density can be controlled using various silicon-containing sources.

Proton conducting molecular species towards the development of polymer electrolyte membranes. KATELYN BRYLL (Washington University in St. Louis St. Louis, MO 63130) SUHAS NIYOGI (Argonne National Laboratory, Argonne, IL, 60439)

A cost effective proton conducting membrane preparation work for a hydrogen fuel cell was done. Membranes were made by attaching two different types of dendrimeric molecules to polyepichlorhydrin and post sulfonation. Besides G1 and G2 that do not have any functional groups, Alt-G1 with ester groupswas used. The amount of the dendrimeric molecule Alt-G1 that was attached to the polymer was varied to optimize the composition. The sulfonic acid contents in these materials were determined and found to be a function of the ratio of [Cl:[Alt-G1] used. It was found that the ratio of 6.67:1 produces an insoluble membrane. Material of two other compositions with the ratios of 1:1 and 3:1 were insoluble in water and gave acid concentrations of 5 meq/g and 1.56 meq/g. The thermal stability of PECH-Alt-G1-SO₃H was found to be higher than that of PECH-G2-SO₃H. Two distinctly different routes were used to synthesize Alt-G2 and only one was met with partial success. New pathways to synthesize Alt-G2 are being worked out.

Separation of Plastics from Shredder Residue by Froth Flotation. SIOBHAN SHAY (Lewis University Romeoville, IL 60446) BASSAM JODY (Argonne National Laboratory, Argonne, IL, 60439)

As landfills in the United States, Europe and Asia become continuously filled, it is necessary for alternatives be found for the material being disposed of in mass quantities. The current objective of the Scrap Recovery and recycling project at Argonne National Lab is to develop an economical method of recovering plastics from end of life vehicles in order to reduce the amount of waste from automobiles in land fills. The current processes that are being investigated are known as froth flotation. The objective of the project is to be able to produce pure enough plastic fractions that meet the requirements for recycling through the use of frothers and depressants at various conditions. Final conclusions can not be made during this time because research has not been completed.

Synthesis of Niobium Selenide Nanoparticles. KYLEE HYZER (University of Missouri-Rolla Rolla, MO 65409) JOHN SCHLUETER (Argonne National Laboratory, Argonne, IL, 60439)

Several attempts were made to synthesize niobium selenide nanoparticles. Common synthetic processes such as reverse micelle synthesis and the introduction of a capping ligand were studied. Various niobium and selenium reagents were used in the synthesis. This study is still being conducted and there are many results of experiments that still must be analyzed.

The Hydrolysis Reaction of the Copper-Chloride Low Temperature Thermochemical Cycle. REBECCA YAPP (Illinois State University Normal, IL 61761) MICHELE LEWIS (Argonne National Laboratory, Argonne, IL, 60439)

Research and development efforts for domestic alternative energy sources are underway. One promising source is hydrogen. Thermochemical cycles are a relatively new technology for producing hydrogen from water. In thermochemical cycles, water and heat are introduced to a series of chemical reactions that operate in a cyclic process. Hydrogen and oxygen are produced and ideally all chemicals are recycled. Thermochemical cycles are of recent interest because of their low greenhouse gas emissions, reasonable efficiency, and compatibility with current nuclear technology. The hybrid copper chloride cycle is one example. This cycle is appealing due in part to its low peak temperature requirement of 550°C. This cycle consists of four reactions; three of which are thermal and the other electrochemical. Two of the thermal reactions are well understood. The hydrolysis of CuCl₂ is represented by the following reaction, 2CuCl₂ + H₂O(g) → CuCl₂oCuO + 2HCl(g). The challenges associated with this reaction are (1) the apparent need for excess water and (2) the presence of a competing reaction. Instead of 0.5 moles of steam required per mole of CuCl₂ up to 40 moles are required. In addition, x-ray diffraction examination shows that some of the CuCl₂ decomposes into CuCl. Cl₂ gas is also observed as a by-product of this competing decomposition reaction. The main goals of this project are to experimentally demonstrate the most efficient set of working conditions for the hydrolysis reaction in order to minimize the amount of water and to eliminate the competing reaction. Experiments are being conducted with three different reactor designs to determine the best conditions for the solid-gas interaction. Variables being studied are the dew point (which is related to the total amount of water), flow rate of the humidified nitrogen, and temperature. Preliminary results demonstrate that the overall reaction occurs faster at higher temperatures but the amount of Cl₂ gas produced also increases. Our results indicate that a reactor design that maximizes the contact area between the CuCl₂ particles and the steam is important.

The Modeling of Porphyrin Supramolecular Assemblies Using Langevin Molecular Dynamics. JOHN MASSEY (Chicago State University Chicago, IL 60628) KRISTY MARDIS (Argonne National Laboratory, Argonne, IL, 60439)

A molecule's conformation determines much of its biological, physical and chemical properties. Therefore, an accurate understanding of these conformations is critical to the understanding of the structure, function and properties of these assemblies. There is a need for methods that resolve the structure and dynamics of supramolecular architectures in solution. One method particularly suited to supramolecular assemblies in solution is high-angle X-ray diffraction. To take full advantage of the data provided through high-angle x-ray diffraction, molecular models of the assemblies must be constructed and their scattering patterns compared to the experimental data. In this work, Langevin dynamics using the Charmm 22 force field were used to construct models of a cyclic Zinc porphyrin hexamer. The goal was to determine if Langevin dynamics could provide accurate models of the solution structure by comparing scattering patterns calculated from the models to the high-angle X-ray diffraction data. Equilibration required relatively high collisional frequencies greater than 20. The models matched the experimental results in the region of 0.01 Å^-1 to 0.6 Å^-1. In the region of 0.6-1.1 Å^-1, the match was to a lesser extent with an additional peak present in the calculated scattering pattern. The high collisional frequencies employed did not allow enough flexibility and kept the structure too close to the starting minimized structure. Longer runs may alleviate this problem. A greater insight into the flexibility of this molecule in solution was gained.