Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session Z34: Hydrogen Production, Storage, Delivery |
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Sponsoring Units: DMP Chair: Zachary Gabelle, Carnagie Institute for Science Room: 210A |
Friday, March 6, 2015 11:15AM - 11:27AM |
Z34.00001: Gettering of Hydrogen and Methane from a Helium Gas Mixture Rosa E. Cardenas, Donald F. Cowgill, Kenneth D. Stewart In this study, we developed an approach for accurately quantifying the helium content in a gas mixture also containing hydrogen and methane using commercially available getters. We performed a systematic study to examine how both H2 and CH4 can be removed simultaneously from the mixture using two SAES St 172$^{\textregistered}$ getters operating at different temperatures. The remaining He within the gas mixture can then be measured directly using a capacitance manometer. The optimum combination involved operating one getter at 650$^{\circ}$C to decompose the methane, and the second at 110$^{\circ}$C to remove the hydrogen. This approach eliminated the need to reactivate the getters between measurements, thereby enabling multiple measurements to be made within a short time interval, with accuracy better than 1{\%}. We anticipate that such an approach will be particularly useful for quantifying the He-3 in mixtures that include tritium, tritiated methane, and helium-3. The presence of tritiated methane, generated by tritium activity, often complicates such measurements. [Preview Abstract] |
Friday, March 6, 2015 11:27AM - 11:39AM |
Z34.00002: Effects of the Electronic Doping In the Stability of the Metal Hydride NaH Monica-Araceli Olea-Amezcua, Juan-Francisco Rivas-Silva, Omar de la Pe\~na-Seaman, Rolf Heid, Klaus-Peter Bohnen Despite metal hydrides light weight and high hydrogen volumetric densities, the Hydrogen desorption process requires excessively high temperatures due to their high stability. Attempts for improvement the hydrogenation properties have been focus on the introduction of defects, impurities and doping on the metal hydride. We present a systematic study of the electronic doping effects on the stability of a model system, NaH doped with magnesium, forming the alloying system Na$_{1-x}$Mg$_{x}$H. We use the density functional theory (DFT) and the self-consistent version of the virtual crystal approximation (VCA) to model the doping of NaH with Mg. The evolution of the ground state structural and electronic properties is analyzed as a function of Mg-content. The full-phonon dispersion, calculated by the linear response theory (LRT) and density functional perturbation theory (DFPT), is analyzed for several Mg-concentrations, paying special attention to the crystal stability and the correlations with the electronic structure. Applying the quasiharmonic approximation (QHA), the free energy from zero-point motion is obtained, and its influence on the properties under study is analyzed. [Preview Abstract] |
Friday, March 6, 2015 11:39AM - 11:51AM |
Z34.00003: High Efficiency, Surface Stable Photocatalytic H2 evolution on TiO2-passivated GaAs Jing Qiu, Guangtong Zeng, Stephen B. Cronin III-V compounds, such as GaAs, are used widely for high efficiency photovoltaic solar energy conversion. The electrochemical instability of these materials, however, has limited their applicability in photocatalysis. Here, we demonstrate that thin (1-5nm) films of TiO2 deposited by atomic layer deposition on planar GaAs provide electrochemical stability and substantial improvements in the efficiency of photocatalytic water splitting. The TiO2-passivated GaAs shows no photochemical degradation or corrosion after 48 hours, while bare GaAs shows substantial degradation after just 15 minutes. This TiO2 passivation layer produces a 32-fold enhancement over bare GaAs, with an overall photoconversion efficiency of 11\%. We find that just 1nm of TiO2 produces the optimum conditions for photocatalysis. This is not thick enough to form a continuous film, and instead produces small regions of non-stiochiometric TiOx, which is rich with Ti3+ surface states that are known to be catalytically active sites. These charged sites stabilize, or lower the energy of, OH- intermediate species in this reaction, thus lowering the reaction barrier height. X-ray photoemission spectroscopy and photoluminescence spectroscopy provide further evidence for these Ti3+ surface states. [Preview Abstract] |
Friday, March 6, 2015 11:51AM - 12:03PM |
Z34.00004: Aging Effects on the Hydrogen Storage Characteristics of Li-Mg-B-N-H Complex Hydrides Sesha Srinivasan, Eric Vickers, James Mulharan, Ghazi Darkazalli, Yogi Goswami, Elias Stefanakos The aging effects on the hydrogen storage characteristics and chemical formulations of the complex hydrides are discussed in this study. The aging effects due to atmospheric events such as oxygen and moisture coverage and self-decomposition are currently under investigation. The candidate material chosen for this study is Lithium/Magnesium based complex hydride LiBH$_{\mathrm{4}}$/LiNH$_{\mathrm{2}}$/MgH$_{\mathrm{2}}$. These materials were prepared using high energy ball milling under Ar/H2 atmosphere with different milling durations. The chemical, structural and microstructural characteristics of the synthesized and aged materials were compared and investigated using TGA/DSC, FTIR, XRD, BET and SEM analytical tools. Hydrogen storage properties such as hydrogen sorption kinetics, cycle life and pressure-composition isotherm (PCI) was examined via high pressure, high temperature Sievert's type apparatus. This current study will shed light to compare and contrast the above mentioned characteristics for the aged samples practically at the same experimental conditions. Furthermore, we have investigated the relationship between the aging effects with respect to the crystallite sizes of the candidate compounds and their nano-dopant variants. [Preview Abstract] |
Friday, March 6, 2015 12:03PM - 12:15PM |
Z34.00005: Molecular simulation of hydrogen storage on hydrogen storage in layered graphite oxide: effect of functional group and intercalated ion Jaehyun Bae, Jisoon Ihm The adsorption of molecular hydrogen gas into layered graphite oxide (GO) has been studied using both classical grand-canonical Monte-Carlo simulations and ab initio calculations. Different from graphite, interlayer distance of graphite oxide can be varied by controlling the functional group density or introducing alkali metal ion in the synthesis process, this gives new ways of searching for efficient hydrogen storage in porous materials. Our ab initio calculations show that average hydrogen binding energy in the graphite oxide layers is enhanced due to the dipole interaction and small hybridization between hydrogen and functional groups. Introducing alkali metal inside the graphite oxide layers further increases average binding energy by 0.1eV and interlayer distance and hydrogen storage capacity increases close to 3wt{\%} at 300K and 10MPa, similar to recent experiments. In the grand-canonical Monte-Carlo simulations, we use ab initio fitted H2-GO and H2-H2 interaction potential and simulation results are understood by equilibrium of interacting gases in the quasi 2-dimensional potential landscape inside the GO layers. Our computational results suggest the best way of synthesizing the optimal chemical and atomic structure of GO for hydrogen storage medium. [Preview Abstract] |
Friday, March 6, 2015 12:15PM - 12:27PM |
Z34.00006: ABSTRACT WITHDRAWN |
Friday, March 6, 2015 12:27PM - 12:39PM |
Z34.00007: Hydrothermal synthesis and characterization of CuFeO2 Delafossite Crystals M. Sarabia, S. Rojas, Z. Lopez-Cabana, R. Villalba, G. Gonzalez, A.L. Cabrera In this study we synthetized CuFeO2 compounds using as precursors Cu2O and FeOOH with fused NaOH. The synthesis takes place is a Teflon vessel lasting 97 (Synthesis I) or 48 hrs (Synthesis II) at 210 $^{\circ}$C. The compound obtained were analyzed for crystal structure and morphology with Raman Sprectroscopy, X-Ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS). Optical properties were obtained by UV-Vis Spectroscopy and Gas adsorption measured with a Quartz-Crystal Microbalance (QCM). Our results show that this type of hydrothermal synthesis is capable to recreate the Delafossite structure of this copper-iron oxide. This material chemisorbs water and carbon dioxide. [Preview Abstract] |
Friday, March 6, 2015 12:39PM - 12:51PM |
Z34.00008: Rapid Facile Microwave-assisted Solvothermal Synthesis of Rod-like CuO/TiO2 for High Efficiency photocatalytic Hydrogen Evolution Yi-Hsien Yu, Ying-Pin Chen, Zhengdong Cheng Rod-like CuO/TiO$_{2}$ was prepared by a rapid facile microwave-assisted solvothermal method for high efficiency photocatalytic hydrogen evolution. The structure of obtained CuO/TiO$_{2}$ samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), and the amount of produced hydrogen was analyzed by gas chromatography (GC). CuO decorated TiO$_{2}$ rods exhibited greatly improvement of photocatalytic hydrogen evolution. Utilizing 30 mg of CuO/TiO$_{2}$ rods sample showed highest hydrogen evolution rate over utilizing 50 mg and 100 mg. Comparing to hydrogen evolution rate of 45.4 $\mu$mol h$^{-1}$ g$^{1}$ by using bare Rod-like TiO$_{2}$, 1 wt{\%} CuO loaded TiO$_{2}$ rods presented the highest hydrogen evolution rate of 3508.7 $\mu$mol h$^{-1}$ g$^{-1}$ while hydrogen evolution rate of 0.5 wt{\%}, 5 wt{\%}, and 10 wt{\%} CuO loaded TiO$_{2}$ rods were 157.1, 2817, and 2595 $\mu$mol h$^{-1}$ g$^{-1}$, respectively. Such enhancement of photocatalytic activity could be ascribed to that CuO improves not only light harvesting but also enhanced separation of electron-hole charge carriers [Preview Abstract] |
Friday, March 6, 2015 12:51PM - 1:03PM |
Z34.00009: The Electrical and Structural analysis of degraded Single Junction Amorphous Silicon Solar Modules Gilbert Osayemwenre This paper outline a systematic approach used in evaluating the quality, performance and reliability of single junction amorphous silicon solar modules (a-Si:H). The analytical techniques include an electrical and structural analysis. These techniques were used to obtain a holistic view of the state of affairs of these readily available PV modules for small stand-alone systems. Specifically, current-voltage (I-V) characterization and scanning electron microscopy (SEM) will be presented as diagnostic tools in this article. The SEM (JEOL, JED-2300) was used to study the surface morphology of the affected region, results show structural damage in the affected regions. The experiment shows that the energy output of the modules varies a degradation variation of 2.5{\%} to 25.7{\%}, was observed. The detailed results will be presented in the final paper. In conclusion, this research established the degradation which occurs and correlate it to the morphological damage. The module with the worst case scenario has an efficiency of 59{\%} decrease, this could be unacceptable in a device where stability is of priority. [Preview Abstract] |
Friday, March 6, 2015 1:03PM - 1:15PM |
Z34.00010: First-principles quantum-mechanical investigations: The role of water in catalytic conversion of furfural on Pd(111) Wenhua Xue, Miguel Gonzalez Borja, Daniel E. Resasco, Sanwu Wang In the study of catalytic reactions of biomass, furfural conversion over metal catalysts with the presence of water has attracted wide attention. Recent experiments showed that the proportion of alcohol product from catalytic reactions of furfural conversion with palladium in the presence of water is significantly increased, when compared with other solvent including dioxane, decalin, and ethanol. We investigated the microscopic mechanism of the reactions based on first-principles quantum-mechanical calculations. We particularly identified the important role of water and the liquid/solid interface in furfural conversion. Our results provide atomic-scale details for the catalytic reactions. [Preview Abstract] |
Friday, March 6, 2015 1:15PM - 1:27PM |
Z34.00011: Study of effects of transport properties of a biodiesel derived from soybean on the mixture process formation using CFD OpenFOAM Adolfo Benitez Molina, Oscar Alejandro de la Garza de Leon, Simon Martinez Martinez, Fausto Alejandro Sanchez Cruz In this work has been studied the effects of the transport properties of biodiesel derived from soybean on the mixing process, using a CFD code OpenFOAM. For this the most relevant properties in this mixing process have been determined: density, viscosity, surface tension and vapor pressure. These fuel properties govern the spray formation however, there are only very limited studies that determined for its subsequent implementation in a CFD code, such as the OpenFOAM code. Such properties were obtained using empirical correlations based on the molecular structure of the fatty acids that compose the biodiesel and applying nonlinear regression are implemented in the programed models used in the OpenFOAM code for a diesel spray simulation. The results achieved in the present study on the one side, have been confirmed how the biodiesel properties affect the mixture process, and on the other side, the obtained coefficients which can be used in the proposed models by the CFD code OpenFOAM for the implementation of this properties as a temperature function without the correlations based on the molecular structure of the fatty acid. [Preview Abstract] |
Friday, March 6, 2015 1:27PM - 1:39PM |
Z34.00012: Catalytic hydrogenation of cresol: first-principles density-functional calculations and \textit{ab initio} molecular dynamics simulations Yaping Li, Zhimin Liu, Friederike Jentoft, Sanwu Wang Biomass is an important renewable energy resource. Cresol is one of components in crude bio-oil generated from biomass, and hydrogenation of cresol is often involved in the upgrading process. We studied catalytic hydrogenation of cresol on the Pt(111) surface with and without the presence of water. In particular, we used first-principles density-functional theory and \textit{ab initio} molecular dynamics simulations to obtain adsorption geometries, binding energies, reaction energies, activation energies, and reaction pathways for hydrogenation of cresol with possible products of 2-methylcyclohexanone and 2-methylcyclohexanol. Our theoretical results are used to explain the available experimental measurements, which show a strong influence of water. [Preview Abstract] |
Friday, March 6, 2015 1:39PM - 1:51PM |
Z34.00013: Hybrid functional calculation of Na and K impurities in CuInSe$_{2}$ and CuIn$_{5}$Se$_{8}$ solar cell materials Janos Kiss, Elaheh Ghorbani, Hossein Mirhosseini, Guido Roma, Claudia Felser Although it is widely known that the presence of Na and K dopants increase the efficiency of CuIn$_x$Ga$_{1-x}$Se (CIGS) thin film solar cells, the incorporation of these impurities and their effect upon the atomic and electronic structure of the light absorber materials is not yet well understood. Using the HSE06 hybrid functional we studied the structure and energetics of Na and K impurities and also Na-Na, K-K and Na-K dumbbells in different substitutional and interstitial positions in CuInSe$_{2}$ and CuIn$_{5}$Se$_{8}$ solar cell materials. We found that among substitutional positions, occupying Cu position is energetically more favorable compared to In and Se positions. The interstitial position, where the impurity is tetrahedrally coordinated by four Se atoms is the most stable site to form Na or K interstitials in CuInSe$_{2}$, wheres in CuIn$_{5}$Se$_{8}$ the pristine copper vacancy positions are more stable. Our data show, that Na-Na, Na-K and K-K dumbbells can form both in CuInSe$_{2}$ and in CuIn$_{5}$Se$_{8}$ as well. Comparing the formation energy of various dumbbell configurations, creating dumbbells in a pristine vacant copper site in CuIn$_{5}$Se$_{8}$ has the highest association energy between the impurities. [Preview Abstract] |
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