Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session S38: Hydrogen Storage and Fuel Cells |
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Sponsoring Units: GERA Room: 385 |
Thursday, March 16, 2017 11:15AM - 11:27AM |
S38.00001: Make America Green Again: Fueling a Cleaner Future with Adsorbed Hydrogen Storage Tanks Andrew Gillespie, Matthew Prosniewski, Ernest Knight, Peter Pfeifer Compressed hydrogen requires extremely high pressures or low temperatures in order to compete with the energy density of conventional fossil fuels. Adsorbent materials provide a means to increase the energy density of the gas up to 3 times that of compressed gas at the same temperature and pressure. Absorbent types are often compared based on their pore structures, surface areas, and heats of adsorption because each of these quantities directly impact storage capacity. In this talk, we compare the deliverable storage capacities of various adsorbent types and discuss the impact that high binding energies have on material performance and delivery. Carbonaceous materials were found to reversibly deliver 2-3 times the amount of hydrogen compared to compressed gas at cryogenic temperatures. [Preview Abstract] |
Thursday, March 16, 2017 11:27AM - 11:39AM |
S38.00002: Functional Nanofiber Composites of Ammonia Borane for Hydrogen Storage Ozge Gunaydin-Sen, Krishna Kharel, Ramanjaneyulu Seemaladinne, Lauren Ware, Suying Wei Temperature dependence of thermal and vibrational properties of Ammonia Borane (NH$_{\mathrm{3}}$BH$_{\mathrm{3}})$ - polymer (e.g. polyacrylamide, polyethylene oxide) composites (in bulk and electrospun nanofiber forms) was measured to understand the structural phase transition behavior and dehydrogenation response. Heat capacity measurements revealed the first-order solid-solid phase transition at 223 K. The transition was suppressed in nanofiber composites which can be attributed to the disruption of the dihydrogen bonding network due to the fiber formation via electrospinning technique. The thermal quantities decreased with the increase in polymer content for the bulk composites. The interaction between the polymer (O of C$=$O or C-O bond) and NH$_{\mathrm{3}}$BH$_{\mathrm{3}}$ (B of B-N bond) could be the cause of the changes. Variable tempearture infrared studies between 400-4000 cm$^{\mathrm{-1}}$ will be discussed to bring insight to this phenomena. Kinetic properties were also investigated to understand the dehydrogenation process between 300-570 K. Activation energies were found to be the smallest for the nanofiber composites reveal the improved kinetics for these new functional materials. The suppression of the unwanted impurities were also supported by the measurements. [Preview Abstract] |
Thursday, March 16, 2017 11:39AM - 11:51AM |
S38.00003: Capping Repels Oxygen and Selectively Adsorbs Hydrogen via Kubas Interaction Rafia Ahmad, Abhishek K. Singh Hydrogen bound via Kubas interaction on metal decorated light weight materials forebodes a much efficient alternative for the fast depleting fossil fuels. O$_2$ interference in hydrogen storage on metal decorated carbonaceous systems remains one of the major stumbling blocks in successful realization of the theoretically promised high storage of Kubas bound H$_{2}$. The interference is a consequence of preferred O$_{2}$ binding at the metal site, thereby blocking it for H$_{2}$ adsorption. Here, we report that arene capping of a Sc-metallacarborane (MCB) efficiently reverses the preferential adsorption of O$_{2}$ over H$_{2}$. The capped Sc-MCB completely repels O$_{2}$ off the Sc-site allowing solely Kubas binding of H$_{2}$, consequent of the down-shift of the ~\textit{d}-band center of Sc from 1.29 eV in the uncapped to 5.67 eV in the capped MCB, below the Fermi-level, respectively. This optimised ~\textit{d}-band center position enables the empty Sc antibonding states to only be available for hydrogen adsorption via Kubas interaction, thereby, to completely avoid oxygen binding. This result provides an approach by tuning a cluster electronically to enhance gas adsorption selectivity, which can be efficiently ulitized in various catalytic, sensing and gas storage systems. [Preview Abstract] |
Thursday, March 16, 2017 11:51AM - 12:03PM |
S38.00004: Dynamic Capacity and Delivery Performance of Adsorbed Hydrogen Tank Technology Ernest Knight, Andrew Gillespie, David Stalla, Matthew Prosniewski, Adam Smith, Peter Pfeifer In an effort to reduce our carbon footprint and decrease our dependency on a finite fuel supply, mankind has been taking steps towards alternative fuel sources. One of the ideal fuel sources worth striving towards is hydrogen. Combusting hydrogen only produces water vapor and hydrogen is incredibly abundant. The largest hurdle of using hydrogen is the storage of the gas itself. Relying solely on compressing the gas requires large heavy gas cylinders for storage. The amount of gas stored at a given pressure can be greatly increased through the use of adsorbent materials. The nanoporous carbon powder we have used has achieved a gravimetric storage capacity of 31 g H$_{2}$/kg C and a volumetric storage capacity of 8.7 g H$_{2}$/L at room temperature and 100 bar. This was measured on our 5.3 L tank filled with our adsorbent material. This powder was able to be packed into the tank in such a way that we achieved a packing fraction of 0.63, which reflects the packing of random close packed spheres. We have used monoliths made from these powders to study the storage capabilities as well as the dynamic filling and discharging performance of our tank. With these monoliths, we are able to obtain a packing fraction of 0.96. We have also been able to measure gravimetric storage capacity of 20.4 g H$_{2}$/kg C and a volumetric storage capacity of 11 g H$_{2}$/L at 195 K and 50 bar on these monoliths. We hope to measure more of this 195 K isotherm as well as thorough isotherm and filling data at 273 K and 296 K. [Preview Abstract] |
Thursday, March 16, 2017 12:03PM - 12:15PM |
S38.00005: Effects of Nano-confinement on Hydrogen Dynamics in TiCl3-Doped NaAlH4 Studied using Quasi-Elastic Neutron Scattering (QENS). Tabbetha Dobbins, Shathabish NaraseGowda, Craig Brown, Madhusudana Tyagi, Timothy Jenkins Dynamics of hydrogen in 4 mol {\%} TiCl3-doped NaAlH4 nanoconfined within the mesoporous SBA15 was studied using QENS. Results show a higher fraction of hydrogen is mobile within these nanoconfined systems relative to bulk TiCl3-doped NaAlH4 but with overall localized motion. Nanostructured Ti-doped NaAlH4 exhibited poorer long-range diffusion kinetics than bulk materials of the same composition. Around 15{\%} of hydrogen participated in long-range motion at 400K (relative to 5{\%} in bulk). Around 65{\%} to 75{\%} of all available hydrogen atoms are mobile at 400K in localized dynamics described by rotation of AlH$_{\mathrm{x}}$ units. Less than 10{\%} hydrogen was mobile at higher temperatures of 420K and 450K, possibly because of the formation of Si-Al phases. Dynamic models indicate that nanostructured samples demonstrated slightly shorter jump lengths (2.09 {\AA} to 2.16 {\AA}) relative to bulk Ti-doped NaAlH4 (2.27 {\AA}). [Preview Abstract] |
Thursday, March 16, 2017 12:15PM - 12:27PM |
S38.00006: Superior performance of borocarbonitrides, $B_{x}C_{y}N_{z}$, as stable, low-cost metal-free electrocatalysts for the hydrogen evolution reaction Himanshu Chakraborty, Manjeet Chhetri, Somak Maitra, Umesh Waghmare, C.N.R. Rao We report superior hydrogen evolution activity of metal-free borocarbonitride (BCN) catalysts. The highly positive onset potential (-56 mV vs. RHE) and the current density of $10 mA cm^{2}$ at an overpotential of 70 mV exhibited by a carbon-rich BCN with the composition $BC_{7}N_{2}$ demonstrates the extraordinary electrocatalytic activity at par with Pt. Theoretical studies throw light on the cause of high activity of this composition. The high activity and good stability of BCN's surpass the characteristics of other metal-free catalysts reported in recent literature. [Preview Abstract] |
Thursday, March 16, 2017 12:27PM - 12:39PM |
S38.00007: Laser Induced Hydrogen Generation from Coal in Water Dovletgeldi Seyitliyev, Khomidkhodzha Kholikov, Ali Er We report an alternative way of obtaining hydrogen using nanosecond laser pulses and various ranks of coal and coke. SEM-EDS analysis shows the atomic concentrations of elements on each of the powders which also is in good agreement with calorimeter analysis. Coal and coke powders were irradiated with 1064nm IR and 532 nm green Nd:YAG pulsed laser beam for 45 minutes. The volume of the total gas generated after irradiation of each rank was measured using the water displacement method. The amount of gas generated increased when using 532 nm compared to 1064 nm. Post-irradiation SEM images show structural differences with samples before irradiation. The amount of gas generation with respect to laser energy density shows nonlinear correlation. Generated gas concentrations were then analyzed using gas chromatography (GC). Hydrogen and carbon monoxide were the two most highly generated gases, and the efficiency of each rank of coal was determined by analyzing the hydrogen to carbon monoxide ratio. The highest efficiency rank was anthracite, with hydrogen to carbon monoxide ratio of 1.4. GC analysis also showed that the maximum hydrogen generation occurs at 100 mJ/pulse laser energy. The efficiency of each rank of coal was observed to correlate with carbon content. [Preview Abstract] |
Thursday, March 16, 2017 12:39PM - 12:51PM |
S38.00008: Structural Dynamics and Activity of Nanocatalysts Inside Fuel Cells by in-operando Atomic Pair Distribution Studies. Binay Prasai We present the results from a study aimed at clarifying the relationship between the atomic structure and activity of nanocatalysts for chemical reactions driving fuel cells, such as the oxygen reduction reaction (ORR). Using in-operando high-energy X-ray diffraction we tracked the evolution of the atomic structure and activity of noble metal-transition metal(NM-TM) nanocatalysts for ORR as they function at the cathode of a fully operational proton exchange membrane fuel cell (PEMFC). Data were analyzed in terms of atomic pair distribution functions and compared to the current output of the PEMFC, which was also recorded during the experiments. The comparison revealed that under actual operating conditions, NM-TM nanocatalysts can undergo structural changes that differ significantly in both length-scale and dynamics and so can suffer losses in their ORR activity that differ significantly in both character and magnitude. Therefore, we argue that strategies for reducing ORR activity losses should implement steps for achieving control not only over the length but also over the time-scale of the structural changes of NM-TM NPs that indeed occur during PEMFC operation. [Preview Abstract] |
Thursday, March 16, 2017 12:51PM - 1:03PM |
S38.00009: First-principles calculations of barium hydride for hydrogen transport applications Andrew Rowberg, Leigh Weston, Chris G. Van de Walle Barium hydride is one of several thermally stable alkaline earth hydrides (AeH$_2$; Ae = Sr, Ca, Ba) to hold potential interest for future hydrogen transport applications, based on its high conductivity of hydride ions over a broad temperature range. However, the underlying materials processes at play in promoting this conductivity remain to be elucidated. A greater understanding of the mechanisms enabling efficient hydride ion migration within BaH$_2$ is needed to move the material closer to applications. Toward that end, we conduct first-principles calculations based on density functional theory with a hybrid functional. We characterize the bulk electronic and structural properties of BaH$_2$ and study the mechanism of hydride ion migration and the influence of native point defects on ionic conductivity. [Preview Abstract] |
Thursday, March 16, 2017 1:03PM - 1:15PM |
S38.00010: First-principles study of oxygen reduction reaction on the tetragonal ZrO$_2$(101) surface Yoshiyuki Yamamoto, Shusuke Kasamatsu, Osamu Sugino ZrO$_2$ has attracted attention as a durable and inexpensive electrocatalyst for future polymer electrolyte fuel cells [1]. Its oxygen reduction reaction (ORR) activity has been made comparable to platinum by introducing oxygen vacancies (Vos) and impurities, such as C and N atoms, but their role is unidentified experimentally. Theoretically, elucidating the ORR activity at a defective oxide surface is a major challenge. In this context, we attacked this problem with first-principles density functional calculations of the tetragonal ZrO$_2$(101) surface adsorbed with water molecules [2]. By investigating various adsorbed configurations, we have found that the surface structure is much more complex than that thought based on a previous calculation [3]. We also found that the pristine surface is not reactive against ORR because of too weak adsorptions of intermediates. On the contrary, the surface becomes reactive when introduced with a Vo and two N atoms at the surface according to our free-energy diagram of ORR. Our calculation also suggests that the defective surface is activated at the surface Vo but not at the surface Zr site. [1] K. Ota et al., ECS Transaction, 45 27(2012). [2] Y. Yamamoto et al., in preparation. [3] A. Hofmann et al., J. Phys. Chem. B, 108 14652(2004). [Preview Abstract] |
Thursday, March 16, 2017 1:15PM - 1:27PM |
S38.00011: In Situ Neutron Diffraction of Rare-Earth Phosphate Proton Conductors Sr/Ca-doped LaPO$_4$ at Elevated Temperatures Amal al-Wahish, Usama al-Binni, C. A. Bridges, A. Huq, Z. Bi, M. P. Paranthaman, S. Tang, H. Kaiser, D. Mandrus Acceptor-doped lanthanum orthophosphates are potential candidate electrolytes for proton ceramic fuel cells. We combined neutron powder diffraction (NPD) at elevated temperatures up to $800\,^\circ\rm{C}$, X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) to investigate the crystal structure, defect structure, thermal stability and surface topography. NPD shows an average bond length distortion in the hydrated samples. We employed Quasi-Elastic Neutron Scattering (QENS) and electrochemical impedance spectroscopy (EIS) to study the proton dynamics of the rare-earth phosphate proton conductors 4.2\% Sr/Ca-doped LaPO$_4$. We determined the bulk diffusion and the self-diffusion coefficients. Our results show that QENS and EIS are probing fundamentally different proton diffusion processes. \newline 1. A. B. al-Wahish et al., Chem. Mater. 28, 7232 (2016). \newline 2. A. B. al-Wahish et al., Rev. Sci. Instrum. 86, 095102 (2015). \newline 3. A. B. al-Wahish et al., J. Phys. Chem. C. 118, 20112 (2014). [Preview Abstract] |
Thursday, March 16, 2017 1:27PM - 1:39PM |
S38.00012: Photoexcitation Mechanism of Metallic Sr$_{1-x}$NbO$_{3}$ for Watersplitting Photocatalyst Masanori Kaneko, Giacomo Giorgi, Koichi Yamashita The absence of a bandgap makes metallic materials not suitable as water-splitting photocatalysts. In 2012, Xu et al. have reported results about Sr-vacancy SrNbO$_{3}$ as a water-splitting photocatalyst.\footnote{X. Xu, et al., \textbf{Nature Materials}, 11, 595 (2012)} Surprisingly, this species is metallic (implying high carrier mobility) with an optical gap of about 1.9 eV and absorb most of the visible light. Authors, by means of DFT based calculations, have predicted its band structure and showed that three bands are separated by a gap: occupied band (B$_{-1}$), partially empty band (CB), and unoccupied band (B$_{1}$). More recently several studies have focused on the energy gap of this class of materials. Nevertheless, the results of the photoexcitation of SrNbO$_{3}$ obtained so far are controversial. Accordingly, we focused my attention on the optical absorption and the position of the bands by means of a DFT analysis. We revealed that photoexcitation around optical gap 1.9 eV is constituted by the CB$\rightarrow$B$_{1}$ transitions on some k-point along the $\Gamma-X$ direction and the most contributed k-point isn't placed in the band-diagram. In addition, we investigated the effect of Sr vacancies and substitutionals on the bandstructure and light absorption. [Preview Abstract] |
Thursday, March 16, 2017 1:39PM - 1:51PM |
S38.00013: A DFT$+$U study on oxygen-vacancy migration in rare-earth doped ceria: the role of 4f electrons. Musa Alaydrus, Mamoru Sakaue, Hideaki Kasai Development of novel fast ion conductors is a crucial issue for realizing solid oxide fuel cells (SOFCs), which can operate in low temperatures, below 600 $^{\mathrm{o}}$C. While yttria-stabilized zirconia (YSZ) had been well-studied both by experiments and theories, exploration of other types of materials retaining high ionic conductivities in lower temperatures is still desired. Here, we studied atomic and electronic properties of oxygen-ionic conduction of M-doped CeO2 based materials (M $=$ La, Pr, Nd, Pm, Sm, Eu, Gd, and Y) by density functional theory (DFT) with Hubbard U correction in. The calculations were performed by considering two cases: (i) strongly localized 4f electrons, (i.e. f electrons are kept frozen in the core) and (ii) f electrons as valence electrons which requires many-body quantum mechanical treatments. The study suggests that balancing (meta-)stable energies can be considered as a key to optimize ionic mobility in doped CeO2. These energies are strongly associated with ionic/covalent interactions in the system. In the presentation we will show that fundamental aspects of the ionic/covalent interactions can only be explained in terms of variable occupancy of empty 4f orbitals. [Preview Abstract] |
Thursday, March 16, 2017 1:51PM - 2:03PM |
S38.00014: Dealloying Behavior of NiCo and NiCoCu Thin Films Benjamin Peecher, Jennfer Hampton Porous metals and alloys, such as those fabricated via electrochemical dealloying, are of interest for a variety of energy applications. Here, the electrochemical dealloying process was explored for electrodeposited binary NiCo and ternary NiCoCu thin films. For four different metal ratios, films were dealloyed using linear sweep voltammetry to various potentials to gain insight into the evolution of the film over the course of the linear sweep. The structure and composition of each sample were examined before and after linear sweep voltammetry was performed. For NiCo films, dealloying resulted in almost no change in composition but did result in an increased capacitance, indicating the removal of material from the films. Dealloying also resulted in the appearance of large pores on the surface of the high Ni percentage NiCo films, while low Ni percentage NiCo films had little observable change in morphology. For NiCoCu films, Cu was almost completely removed at linear sweep potentials greater than 0.5 V versus Ag/AgCl. The linear sweep removed large Cu-rich dendrites from the films, while also causing increases in measured capacitance. [Preview Abstract] |
Thursday, March 16, 2017 2:03PM - 2:15PM |
S38.00015: Realizing nanographene activated by a vacancy to solve hydrogen storage problem Gagus Ketut Sunnardianto, Isao Maruyama, Koichi Kusakabe We found a triply hydrogenated vacancy (V$_{\mathrm{111}})$ in nanographene reduces an activation barrier of adsorption-desorption process in both ways in an equal manner from the known values for pristine graphene as well as those of other hydrogenated vacancies of graphene. This finding may give a key to overcome existing problems in the hydrogen uptake and release processes in known hydrogen storage materials, e.g. graphene and organic hydrides (OHs) in near ambient operation temperature. In this study, we used DFT-NEB simulation to estimate the barrier height, which is supported by realized real experiments. We consider a nanographene molecule (VANG) which contains V$_{\mathrm{111}}$ with armchair structure at the periphery. We found interesting feature in comparable values of energy barriers for both hydrogen uptake and release, where hydrogenation process is even a little bit endothermic and dehydrogenation is a little but exothermic nature. Thus, this material structure acts as ``self-catalytic properties'', which has an important role in reducing an energy barrier and as a trapping site for hydrogen serving a new material prevailing other hopeful candidates. [Preview Abstract] |
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