Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session M22: Hydrogen Storage, Transportation & Novel PV |
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Sponsoring Units: GERA Chair: Peter Pfeifer, University of Missouri Room: 407 |
Wednesday, March 5, 2014 11:15AM - 11:27AM |
M22.00001: Electrification of the transportation sector offers limited country-wide greenhouse gas reductions Christoph J. Meinrenken, Klaus S. Lackner Compared with conventional propulsion, plugin and hybrid vehicles may offer reductions in greenhouse gas (GHG) emissions, regional air/noise pollution, petroleum dependence, and ownership cost. Comparing only plugins and hybrids amongst themselves, and focusing on GHG, relative merits of different options have been shown to be more nuanced, depending on grid-carbon-intensity, range and thus battery manufacturing and weight, and trip patterns. We present a life-cycle framework to compare GHG emissions for three drivetrains (plugin-electricity-only, gasoline-only-hybrid, and plugin-hybrid) across driving ranges and grid-carbon-intensities, for passenger cars, vans, buses, or trucks (well-to-wheel plus storage manufacturing). Parameter and model uncertainties are quantified via sensitivity analyses. We find that owing to the interplay of range, GHG/km, and portions of country-wide kms accessible to electrification, GHG reductions achievable from plugins (whether electricity-only or hybrids) are limited even when assuming low-carbon future grids. Furthermore, for policy makers considering GHG from electricity and transportation sectors combined, plugin technology may in fact increase GHG compared to gasoline-only-hybrids, regardless of grid-carbon-intensity. [Preview Abstract] |
Wednesday, March 5, 2014 11:27AM - 11:39AM |
M22.00002: High-pressure, ambient temperature hydrogen storage in metal-organic frameworks and porous carbon Matthew Beckner, Anne Dailly We investigated hydrogen storage in micro-porous adsorbents at ambient temperature and pressures up to 320 bar. We measured three benchmark adsorbents: two metal-organic frameworks, Cu$_{\mathrm{3}}$(1,3,5-benzenetricarboxylate)$_{\mathrm{2}}$ [Cu$_{\mathrm{3}}$(btc)$_{\mathrm{2}}$; HKUST-1] and Zn$_{\mathrm{4}}$O(1,3,5-benzenetribenzoate)$_{\mathrm{2}}$ [Zn$_{\mathrm{4}}$O(btb)$_{\mathrm{2}}$; MOF-177], and the activated carbon MSC-30. In this talk, we focus on adsorption enthalpy calculations using a single adsorption isotherm. We use the differential form of the Claussius-Clapeyron equation applied to the Dubinin-Astakhov adsorption model to calculate adsorption enthalpies. Calculation of the adsorption enthalpy in this way gives a temperature independent enthalpy of 5-7 kJ/mol at the lowest coverage for the three materials investigated. Additionally, we discuss the assumptions and corrections that must be made when calculating adsorption isotherms at high-pressure and adsorption enthalpies. [Preview Abstract] |
Wednesday, March 5, 2014 11:39AM - 11:51AM |
M22.00003: Liquid-like hydrogen densities in engineered carbon nanospaces Elmar Dohnke, Andrew Gillespie, Peter Pfeifer High surface area materials, such as those engineered from synthetic carbon compounds, have narrow pore sizes resulting in exceptionally high stored densities for hydrogen. Stored density is a measurement of the average hydrogen density within a pore. At supercritical temperatures and high pressures, these materials can achieve stored densities 20{\%} higher than liquid hydrogen at 1 bar and 20 K. At 77 K and 200 bar, we have achieved stored densities of up to 85 g/L. We can show, depending on the pore structure, a maximum of gravimetric hydrogen excess adsorption at 100 bar and 296 K and binding energies of 8-10 kJ/mol. The occurrence of a maximum of gravimetric excess adsorption at relatively low pressures, indicating a high binding energy, is due to the overlapping adsorption potentials in narrow pores. [Preview Abstract] |
Wednesday, March 5, 2014 11:51AM - 12:03PM |
M22.00004: Hydrogen spillover mechanism on covalent organic frameworks as investigated by DFT Hong Zhang The hydrogen spillover mechanism, including the H chemisorption, diffusion, and H$_{2}$ associative desorption on the surface of COFs and H atoms migration from metal catalyst to COFs, have been studied via DFT. The results described herein show that each sp$^{2}$ C atom on COFs' surface can adsorb one H atom with the bond length d$_{C-H}$ between 1.11 and 1.14 {\AA}, and the up-down arrangement of the adsorbed H atoms is the most stable configuration. By counting the chemisorptions binding sites for these COFs, we predict the saturation storage densities. High hydrogen storage densities can be found that the gravimetric uptakes of COFs are in the range of 5.13 $\sim$ 6.06 wt{\%}. The CI-NEB calculations reveal that one H atom diffuse along C-C path on HHTP surface should overcome 1.41 $\sim$ 2.16 eV energy barrier. We choose tetrahedral Pt$_{4}$ cluster and HHTP as the representative catalyst and substrate, respectively, to study the H migration from metal cluster to COFs. [Preview Abstract] |
Wednesday, March 5, 2014 12:03PM - 12:15PM |
M22.00005: Adsorption Enthalpies of Hydrogen on Chemically Enhanced Carbon Nanospaces Andrew Gillespie, Elmar Dohnke, Joseph Schaeperkoetter, David Stalla, Peter Pfeifer Chemical functionalization of carbon nanopore spaces has been shown to significantly increase the differential enthalpy of adsorption of hydrogen (ca. 9kJ/mol). This improved surface interaction corresponds to an increased density of the adsorbed film. Functionalized carbon samples have been produced through KOH activation, deposition of decaborane, and high temperature annealing. Hydrogen sorption measurements have shown significant improvements to stored film densities and binding energies. In this talk, a systematic study of the effect that boron concentration has on the samples' pore structures, binding energies, surface excess concentrations, and volumetric storage capacities is presented. [Preview Abstract] |
Wednesday, March 5, 2014 12:15PM - 12:27PM |
M22.00006: Comparative analysis of density functional theory for hydrogen adsorption on metalloporphyrin incorporated graphenes Yungok Ihm, Changwon Park, Yong-Hyun Kim, Mina Yoon Porphyrins are often found in nature. The center of the molecules is chemically highly active, thus they can accommodate various metals with high structural stability. A recent study using density functional theory (DFT) suggests that metal incorporated porphyrins can store H$_{\mathrm{2}}$ in significant amounts at the uniformly distributed metal centers, indicating their great potential as a material for hydrogen storage. In this work, we evaluate the performance of DFT exchange-correlation (XC) functionals to describe the properties of hydrogen adsorption on porphyrin-incorporated graphenes (PIG). We studied PIGs doped with different metals (Mg, Ca, Zn, Ti, V) using various XC functionals, ranging from LDA to van der Waals corrected functionals. Metals interacting with hydrogen through chemical binding, dominated by the Cubas mechanism, have a hydrogen binding strength with much stronger dependence on the XC functional than van der Waals systems. The specific shape of the hydrogen energy potential near metal centers is important in determining the thermodynamic stabilities of the hydrogen adsorption and desorption mechanism. The insights obtained in this work should be useful also when applying DFT methods to more generalized adsorption systems. [Preview Abstract] |
Wednesday, March 5, 2014 12:27PM - 12:39PM |
M22.00007: ABSTRACT WITHDRAWN |
Wednesday, March 5, 2014 12:39PM - 12:51PM |
M22.00008: High Density Methane Storage in Nanoporous Carbon Tyler Rash, Elmar Dohnke, Yuchoong Soo, Brett Maland, Plamen Doynov, Yuyi Lin, Peter Pfeifer Development of low-pressure, high-capacity adsorbent based storage technology for natural gas (NG) as fuel for advanced transportation (flat-panel tank for NG vehicles) is necessary in order to address the temperature, pressure, weight, and volume constraints present in conventional storage methods (CNG {\&} LNG.) Subcritical nitrogen adsorption experiments show that our nanoporous carbon hosts extended narrow channels which generate a high surface area and strong Van der Waals forces capable of increasing the density of NG into a high-density fluid. This improvement in storage density over compressed natural gas without an adsorbent occurs at ambient temperature and pressures ranging from 0-260 bar (3600 psi.) The temperature, pressure, and storage capacity of a 40 L flat-panel adsorbed NG tank filled with 20 kg of nanoporous carbon will be featured. [Preview Abstract] |
Wednesday, March 5, 2014 12:51PM - 1:03PM |
M22.00009: Investigation of Morphology and Hydrogen Adsorption Capacity of Disordered Carbons Lilin He, Yuri Melnichenko, Nidia Gallego, Cristian Contescu We have applied small angle neutron scattering (SANS) technique to study the morphologies and hydrogen adsorption capabilities of wood-based ultramicroporous carbon and poly(furfuryl alcohol) derived carbon. The Polydispersed Spherical model and chord length analysis of the scattering profiles were performed to obtain morphological parameters such as average pore size and pore size distribution of the dry carbons, which agreed reasonably well with the independent gas sorption measurements. The hydrogen physisorbed in these two carbons at room temperature and moderate pressures was investigated by In-situ SANS measurements. The experimental data analyzed using a modified Kalliat model for decoupling scattering contributions from pores with different sizes indicates that the molecular hydrogen condenses preferentially in narrow micropores at all measured pressures, which supports the theoretical prediction by quantum mechanical and thermodynamical models. [Preview Abstract] |
Wednesday, March 5, 2014 1:03PM - 1:15PM |
M22.00010: Determination of Hydrogen absorption capacity of different nanomaterials using a Quartz Crystal Microbalance Susana Rojas, Donovan Diaz-Droguett, Alejandro Cabrera Hydrogen has become an alternative energy source and a key gas for the fuel cell technology. For these reasons, there is a growing need of developing more efficient materials for hydrogen storage in a safer way and to develop hydrogen sensors for hydrogen detection. We studied hydrogen absorption properties of different nanomaterials-assembled systems using a Quartz Crystal Microbalance. The nanomaterials inspected include palladium-based thin films, metal oxides, polymer-metal composites as well as carbon nanoparticles. [Preview Abstract] |
Wednesday, March 5, 2014 1:15PM - 1:27PM |
M22.00011: Infrared absorption enhancement at nickel-silicide/silicon interfaces Jordan Hachtel, Rohan Mishra, Sokrates Pantelides, Stephen Pennycook Nanoparticle embedded thin films are of interest because they have been predicted to enhance absorption and improve thin-film photovoltaic devices. For the case of nickel silicide nanoparticles embedded in amorphous silicon there is experimental observation of absorption enhancement, especially in the infrared where the solar spectrum is strong, but silicon absorption is weak. However, it is not known whether this enhancement is due to effects at the silicide/silicon interface that can actually be applied to photovoltaic devices or simply bulk absorption into the metal. To study these effects, we created theoretical supercells of the interface between nickel di-silicide and silicon, and calculate the optical properties using density functional theory. The supercells show a strong absorption enhancement peak in the red/near-IR, which is the optimal region for absorption. An analysis of the DOS reveals that shifts in the dominant nickel d-orbitals create interface transitions in the IR that are unavailable in the bulk. [Preview Abstract] |
Wednesday, March 5, 2014 1:27PM - 1:39PM |
M22.00012: Using surfaces, ligands, and dimensionality to obtain desired nanostructure properties Prashant Nagpal, Vivek Singh, Yuchen Ding Nanostructured materials are intensively investigated to obtain material properties different from their bulk counterparts. It has been demonstrated that nanoscaled semiconductor can have interesting size, shape and morphology dependent optoelectronic properties. But the effect of surfaces, ligands and dimensionality (0D quantum dots to 2D nanosheets) has been largely unexplored. Here, we will show how tuning the surface and dimensionality can affect the electronic states of the semiconductor, and how these states can play an important role in their fundamental photophysical properties or thermal transport. Using the specific case for silicon, we will show how ``new'' surface states in small uniform can lead to light absorption/emission without phonon assistance, while hindering the phonon-drag of charge carriers leading to low Seebeck coefficient for thermoelectric applications. These measurements will shed light on designing appropriate surface, size, and dimensionality for desired applications of nanostructured films. [Preview Abstract] |
Wednesday, March 5, 2014 1:39PM - 1:51PM |
M22.00013: Selective Defects Passivation of GaInNAs Solar Cells by Hydrogenation Miwa Fukuda, Vincent R. Whiteside, Ian R. Sellers, Mohamed Al Khalfioui, Mathieu Leroux, Lucas Phinney, Khalid Hossain While GaInNAs has the potential to be a fourth-junction in multi-junction solar cells it has proved difficult to achieve the optimal alloy composition due to the low solubility of nitrogen in these materials. At this point we investigate the possibility of improving the performance of GaInNAs using hydrogenation to selectively passivate mid-gap defects, while preserving the functionality of substitutional nitrogen. Temperature dependent photoluminescence measurements of the intrinsic region of a GaInNAs p-i-n solar cell show a classic ``s-shape'' associated with localization prior to hydrogenation, while after hydrogenation no sign of the ``s-shape'' is evident. The preliminary investigations of the effect of hydrogenation on the efficiency of carrier transport in the solar cells will also be presented. Amethyst Research Inc.'s photon-assisted defect mitigation-hydrogenation technique is usually a low temperature process; however, the annealing effects will be de-convoluted from that of hydrogenation. [Preview Abstract] |
Wednesday, March 5, 2014 1:51PM - 2:03PM |
M22.00014: Study of LO-phonon decay in semiconductors for hot carrier solar cell Hugo Levard, Julien Vidal, Sana Laribi, Jean-Fran\c{c}ois Guillemoles Knowledge of phonon decay is of crucial importance when studying basic properties of semiconductors, since they are closely related to Raman linewidth and non-equilibrium-hot-carriers cooling. The latter indeed cools down to the bottom of the conduction band within a picosecond range because of electron-phonon interaction. The eventual emitted hot phonons then decay in few picoseconds. The hot carriers cooling can be slowed down by considering the decay rate dependence of phonon on conservation rules, whose tuning may reduce the allowed two-phonon final states density. This is of direct interest for the third generation photovoltaic devices that are Hot Carrier Solar Cells (HCSC), in which the photoexcited carriers are extracted at an energy higher than thermal equilibrium. One of the HCSC main challenges then is to find an absorber material in which the hot phonons has a relaxation time longer than the carriers cooling time, so that we can expect the electron to ``reabsorb'' a phonon, slowing down the electronic cooling. HCSC yield is ultimately limited by LO phonon decay, though. In this work, we present theoretical results obtained from ab initio calculations of phonon lifetime in III-V and IV-IV semiconductors through a three-phonon process. Common approximations in the literature are questioned. In particular, we show that the usual ``zone-center approximation'' is not valid in some specific semiconductors. The analysis allows to correctly investigate phonon decay mechanisms in bulk and nanostructured materials. [Preview Abstract] |
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