Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session A20: Energy MaterialsFocus
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Sponsoring Units: GERA Chair: Deyu Lu, Brookhaven National Laboratory Room: LACC 308B |
Monday, March 5, 2018 8:00AM - 8:36AM |
A20.00001: Meeting the Growing Need for Long-Duration Energy Storage Invited Speaker: Yet-Ming Chiang The growing deployment of variable renewables has created both need and opportunity for affordable energy storage that cycles over multi-day and longer durations. Low-cost generation combined with storage that adds a per-cycle cost of $0.03/kWh$ or less to the levelized cost of renewable electricity could enable renewable power plants that can compete on cost with fossil fuel generation. Since long-duration storage implies fewer cycles over the system lifetime, the required capital cost is inversely proportional to duration. Storage technologies are needed that have exceptionally low cost of stored energy, while operating at much lower C-rates than typical battery applications. Flow batteries have the flexibility of design to meet these requirements, but only if the underlying chemical cost of storage is low enough. This talk will give examples of use-case and techno-economic analyses that help to define requirements for long-duration storage, and discuss electrochemistries with the potential to meet long-duration requirements. Aqueous sulfur-based flow batteries are one such class, for which recent research progress will be reported. |
Monday, March 5, 2018 8:36AM - 8:48AM |
A20.00002: MXenes/Graphene Heterostructures for Li Battery Applications: A Frist Principles Study Yierpan Aierken, Cem Sevik, Oguz Gulseren, François Peeters, Deniz Cakir
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Monday, March 5, 2018 8:48AM - 9:00AM |
A20.00003: Multi-Stage Structural Transformations in Zero-Strain Lithium Titanate Unveiled by in Situ X-ray Absorption Fingerprints Deyu Lu, Mehmet Topsakal, Wei Zhang, Feng Wang, Amy Marschilok, Esther Takeuchi Zero-strain electrodes, such as spinel lithium titanate (Li4/3Ti5/3O4), are appealing for application in batteries due to their negligible volume change and extraordinary stability upon repeated charge/discharge cycles. This same property, however, makes it challenging to probe their structural changes during the electrochemical reaction. We report combined studies of lithiation-driven structural transformations in Li4/3Ti5/3O4 using in situ X-ray absorption spectroscopy and ab initio calculations. Based on excellent agreement between computational and experimental spectra of Ti K-edge, we identified key spectral features as fingerprints for quantitative assessment of structural evolution at different length scales. Results from this study indicate that, despite the small change in the crystal lattice, pronounced structural transformations occur in Li4/3Ti5/3O4, both locally and globally, giving rise to a multi-stage kinetic process involving mixed quasi-solid solution/macroscopic two-phase transformations over a wide range of Li concentrations. |
Monday, March 5, 2018 9:00AM - 9:12AM |
A20.00004: Exploring the Potential of Metal-Doped Graphene as Improved Electrocatalysts for CO2 Reduction Using Embedded Mean-Field Theory Leanne Chen, Thomas Miller Carbon-based materials are particularly interesting potential electrocatalysts for CO2 reduction due to their low cost and ability to form a wide range of nanostructures. Numerous studies have shown single metal atoms embedded in a conductive graphene network to exhibit unique electrocatalytic properties. These systems present a computational challenge because, in contrast to an extended metallic surface, the electronic structure of the active site in metal-doped graphene is localized and thus requires a density functional theory (DFT) treatment beyond the generalized-gradient approximation (GGA) level. However, higher-level (e.g., hybrid-DFT) methods conducted on the whole system are prohibitively expensive. In this work, we use embedded mean-field theory (EMFT) to overcome the challenges of accurately modeling the electrocatalytic activity of metal-doped graphene at reasonable computational cost. We show that EMFT enables efficient exploration of metal-doped graphene as potentially improved electrocatalysts over pure transition metals for CO2 reduction. |
Monday, March 5, 2018 9:12AM - 9:24AM |
A20.00005: Complete Inhibition of Pt Site Poisoning and Efficient Carbon Monoxide Oxidation Induced by Vanadium and Cobalt Rafia Ahmad, Abhishek Singh A complete solution for CO poisoning of Pt catalysts, requires a design that entirely prevents CO adsorption on Pt atoms. We explored the CO adsorption sites and oxidation capability of 3d transition metal doped small magic clusters of Pt4. Among Pt3M, only Pt3V free-standing cluster entirely eliminates the prospect of Pt poisoning by inverting the adsorption site of CO to V atom. V d-band center lies closer to the Fermi-level than that of Pt atoms, resulting in larger number of empty d-antibonding states, thereby, making V comparatively more reactive towards CO. The inversion of CO adsorption site, is also observed for larger PtnVm clusters and becomes possible for PtnCom clusters for sizes larger than m+n=12. A maximum catalytic efficiency is attained for Pt41V14, which at room temperature gives a CO2 turn over frequency comparable to the conventional catalysts. The oxidation of CO becomes more favourable by Mars van Krevelan than Langmuir Hinshelwood mechanism for the cluster supported on vacancy prone Li-doped MgO(100). Our results present a rationale design of Pt poisoning free fuel cells and automobile exhaust catalyst. |
Monday, March 5, 2018 9:24AM - 9:36AM |
A20.00006: Abstract Withdrawn
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Monday, March 5, 2018 9:36AM - 9:48AM |
A20.00007: Interplay of TM and Ligand Density of States of Li-Ion Battery Cathode Materials and Its Implications on Structure and Spectroscopy Ilkyu Lee, Chunjing Jia, Brian Moritz, Thomas Devereaux The field of rechargeable batteries has gained incredible attention due to Lithium-ion transition metal compounds and their attractive properties such as high energy density and low self-discharge. However, limitations still exist in optimizing cathode material design due to a lack of deep understanding of the physics behind processes that occur during delithiation and their implications on structure and electrochemistry. In this study, we analyze the interplay of TM and ligand orbitals and relative positioning of their density of states using a many-body cluster model. We also use the model to simulate spectroscopy to gain insight on how the interaction of the TM and ligand bands can lead to certain signature features in the spectra and how such features can be directly correlated to structural changes upon delithiation. By analyzing the connection between the simple single-electron picture of density of states and crucial processes that occur during delithiation, we aim to achieve a greater understanding of the fundamental physics of Li-ion cathode materials, in hopes of predicting novel, better performing Li-ion compounds. |
Monday, March 5, 2018 9:48AM - 10:00AM |
A20.00008: Theoretical and experimental understanding of electrochemical carbon deposition on nickel and ceria electrodes in solid-oxide fuel cells. Michal Bajdich, Theis Skafte, Max Garcia-Melchor, William Chueh, Christopher Graves Nickel-based electrodes and catalysts are often utilized in high-temperature electrochemical CO2 reduction due to their high performance and low cost. However, nickel is also an excellent catalyst for destructive carbon deposition, which can be mitigated by the use of ceria. In this work, we elucidate the inhibition mechanism during electrochemical CO2 reduction on dense thin-film model-electrodes consisting of samarium-doped ceria, nickel, and yttria-stabilized zirconia. The results obtained via operando x-ray photoelectron spectroscopy show hat ceria- based electrodes require higher onset overpotentials for carbon deposition and have a high surface coverage of carbonate species. Our density functional theory calculations reveal the crucial role of the surface carbonates as energetic traps that inhibit carbon formation and show that this is most effective with non-stoichiometric CeO2-δ(100) surfaces. This destabilization of carbon leads to a thin amorphous carbon layer instead of the destructive carbon nanotubes that grow on nickel without ceria present. |
Monday, March 5, 2018 10:00AM - 10:12AM |
A20.00009: Ab-initio Raman spectra of Cu2SnS3 and Cu2GeS3 and their (Sn,Ge) alloys Ludger Wirtz, Henrique Miranda, Erika Robert, Phillip Dale The ternary materials Cu2SnS3 (CTS) and Cu2GeS3 (CGS) are currently being considered as potential candidates for absorber layers in solar cells. Their crystalline structure is close to the one of zinc-blende ZnS with two third of zinc atoms replaced by Cu atoms and one third by Ge/Sn, respectively. However, due to the symmetry breaking, the Raman spectra of CTS and CGS display a plethora of peaks. |
Monday, March 5, 2018 10:12AM - 10:24AM |
A20.00010: High Capacity Lithium Ion Batteries Composed of Cobalt Oxide Nanoparticle Anodes and Raman Spectroscopic Analysis of Nanoparticle Strain Dynamics in Batteries Mohammad Islam, Mateusz Zuba, Vincent Debiase, Nicholas Noviasky, Christopher Hawley Cobalt nanoparticle thin films were electrophoretically deposited on copper current collectors and were annealed into thin films of hollow Co3O4 nanoparticles. These thin films were directly used as the anodes of lithium ion batteries without the addition of conducting carbons and bonding agents. Lithium ion batteries thus fabricated show high gravimetric capacities and long cycle lives. For »1.0 μm thick Co3O4 nanoparticle films the gravimetric capacities of the batteries were more than 800 mAh/g at a current rate of C/15 which is about 90% of the theoretical maximum. Additionally, the batteries were able to undergo 200 charge/discharge cycles at relatively fast rate of C/5 and maintain 50% of the initial capacitance. In order to understand the electrochemistry of lithiation in the context of nanoparticles, Raman spectra were collected at different stages of the electrode cycles to determine the chemical and structural changes in the nanomaterials. Our results indicate that initially the electrode nanoparticles are under significant strain and as the battery undergoes many cycles of charging/discharging the nanoparticles experience progressive strain relaxation. |
Monday, March 5, 2018 10:24AM - 10:36AM |
A20.00011: Fundamental limits of nonlinear optical processes in semiconductors: shift photocurrents and second harmonic generation Liang Tan, Andrew Rappe Second harmonic generation and shift currents are nonlinear optical effects occurring in noncentrosymmetric materials. The shift current is responsible for the generation of photocurrents in the bulk of single-phase materials, resulting in advantages over traditional photovoltaics, such as above-band gap photovoltages, and bulk photocurrent generation without the need for interface engineering. Despite numerous theoretical and experimental research efforts into these nonlinear optical effects, there has been no systematic investigation into their maximum attainable magnitude in solid-state materials. In this talk, we present analytic upper bounds on the second-order optical conductivities of noncentrosymmetric semiconductors. We show that this bound depends on the band gap, band width, and geometrical properties of the material in question, but do not involve its polarization. As a proof of principle, we perform first-principles calculations of the response tensors of a wide variety of materials, finding that the materials in our database do not yet saturate the upper bound. This suggests that new materials with large nonlinear responses will likely be discovered by future materials research guided by the factors mentioned in this work. |
Monday, March 5, 2018 10:36AM - 10:48AM |
A20.00012: Plasmonic Nano-gratings For in situ Nonlinear Optical Spectroelectrochemistry Zhihua Liu, Qian Xu, Hongqing Wang, Fuxin Guan, Huijie Guo, Lei Zhou, YuenRon Shen, Weitao Liu Understanding electrochemical (EC) reactions at the molecular-level is crucial for fundamental science and applications, yet it is highly challenging to probe the buried interfaces between electrodes and electrolyte. Previously by exploiting the surface plasmon (SP) enhancement, we successfully monitored molecular signatures of EC reactions in situ with the surface-specific sum-frequency vibration spectroscopy (SFVS). However, the SP suffers from severe attenuation toward absorption bands of electrolytes. Here we show that metal electrodes engraved with plasmonic nano-gratings can provide a general solution for SFVS of EC interfaces. With optimal composition and geometry, the nano-gratings can efficiently compensate for the electrolyte attenuation, and lead to strong near-field enhancement highly specific to electrode/electrolyte interfaces. Using a gold nano-gratings electrode, we demonstrate the in situ SFVS in the midst of strong absorption bands of the water electrolyte, and unveiled sequential changes of the hydrogen bonding network of interfacial water molecules during redox cycling of gold, showing that our approach offers a powerful tool toward the microscopic and mechanistic understanding of EC interfaces. |
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