Investigation of the Potential Energy Surface for the First Step in the Alkaline Hydrolysis of Methyl Acetate

The potential energy surface for the first step of the alkaline hydrolysis of methyl acetate was explored by a variety of methods. The conformational search routine within SPARTAN was used to determine the lowest energy am1 and pm3 structures for the anionic tetrahedral intermediate. Ab initio single point and geometry optimization calculations were performed to determine the lowest energy conformer, and the linear synchronous transition (lst) method was used to provide an initial structure for transition state optimization. Transition states were obtained at the am1, pm3, 3-21G, and 3-21 + G levels of theory. These transition states were compared with the anionic tetrahedral intermediates to examine the assumption that the intermediate is a good model for the transition state. In addition, the Cramer/Truhlar sm3 solvation model was used at the semiempirical level to compare gas phase and aqueous alkaline hydrolysis of methyl acetate.

A Model to Predict Percolation Threshold and Effective Conductivity of Infiltrated Electrodes for Solid Oxide Fuel Cells

We present a mechanistic modeling methodology to predict both the percolation threshold and effective conductivity of infiltrated Solid Oxide Fuel Cell (SOFC) electrodes. The model has been developed to mirror each step of the experimental fabrication process. The primary model output is the infiltrated electrode effective conductivity which provides results over a range of infiltrate loadings that are independent of the chosen electronically conducting material. The percolation threshold is utilized as a valuable output data point directly related to the effective conductivity to compare a wide range of input value choices. The predictive capability of the model is demonstrated by favorable comparison to two separate published experimental studies, one using strontium molybdate and one using La0.8Sr0.2FeO3-δ as infiltrate materials. Effective conductivities and percolation thresholds are shown for varied infiltrate particle size, pore size, and porosity with the infiltrate particle size having the largest impact on the results.

A Model to Predict Percolation Threshold and Effective Conductivity of Infiltrated Electrodes for Solid Oxide Fuel Cells

We present a mechanistic modeling methodology to predict both the percolation threshold and effective conductivity of infiltrated Solid Oxide Fuel Cell (SOFC) electrodes. The model has been developed to mirror each step of the experimental fabrication process. The primary model output is the infiltrated electrode effective conductivity which provides results over a range of infiltrate loadings that are independent of the chosen electronically conducting material. The percolation threshold is utilized as a valuable output data point directly related to the effective conductivity to compare a wide range of input value choices. The predictive capability of the model is demonstrated by favorable comparison to two separate published experimental studies, one using strontium molybdate and one using La0.8Sr0.2FeO3-delta as infiltrate materials. Effective conductivities and percolation thresholds are shown for varied infiltrate particle size, pore size, and porosity with the infiltrate particle size having the largest impact on the results. (C) 2013 The Electrochemical Society. All rights reserved.

Microscopic and Spectroscopic Methods for Probing the Clay Water Interface

Clay minerals have a fundamental importance in many processes in soils and sediments such as the bioavailability of nutrients, water retention, the adsorption of common pollutants, and the formation of an impermeable barrier upon swelling. Many of the properties of clay minerals are due to the unique environment present at the clay mineral/water interface. Traditional techniques such as X-ray diffraction (XRD) and absorption isotherms have provided a wealth of information about this interface but have suffered from limitations. The methods and results presented herein are designed to yield new experimental information about the clay mineral/water interface.A new method of studying the swelling dynamics of clay minerals was developed using in situ atomic force microscopy (AFM). The preliminary results presented here demonstrate that this technique allows one to study individual clay mineral unit layers, explore the natural heterogeneities of samples, and monitor swelling dynamics of clay minerals in real time. Cation exchange experiments were conducted monitoring the swelling change of individual nontronite quasi-crystals as the chemical composition of the surrounding environment was manipulated several times. A proof of concept study has shown that the changes in swelling are from the exchange of interlayer cations and not from the mechanical force of replacing the solution in the fluid cell. A series of attenuated total internal reflection Fourier transform infrared spectroscopy (ATR-FTIR) experiments were performed to gain a better understanding of the organization of water within the interlayer region of two Fe-bearing clay minerals. These experiments made use of the Subtractive Kramers-Kronig (SKK) Transform and the calculation of difference spectra to obtain information about interfacial water hidden within the absorption bands of bulk water. The results indicate that the reduction of structural iron disrupts the organization of water around a strongly hydrated cation such as sodium as the cation transitions from an outer-sphere complex with the mineral surface to an inner-sphere complex. In the case of a less strongly hydrated cation such as potassium, reduction of structural iron actually increases the ordering of water molecules at the mineral surface. These effects were only noticed with the reduction of iron in the tetrahedral sheet close to the basal surface where the increased charge density is localized closer to the cations in the interlayer.

Development of Solid Oxide Fuel Cell Electrodes with High Conductivity and Enhanced Redox Stability

The intent of this study was the development of new ceramic SOFC anode materials which possess electrical conductivity as well as redox stability.