Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session A38: Focus Session: Instrumentation and Measurement Science for a Sustainable Energy Future |
Hide Abstracts |
Sponsoring Units: GIMS Chair: Eric Palm, National High Magnetic Field Laboratory, Tallahassee Room: 347 |
Monday, March 18, 2013 8:00AM - 8:36AM |
A38.00001: Our Sustainable Earth Invited Speaker: Raymond L. Orbach Recent evidence demonstrates that the Earth has been warming monotonically since 1980. Transient to equilibrium temperature changes take centuries to develop, as the upper levels of the ocean are slow to respond to atmospheric temperature changes. Atmospheric CO$_{\mathrm{2}}$ concentrations, from ice core and observatory measurements, display consistent increases from historical averages, beginning in about 1880. They can be associated with the use of coal ecause of the spread of the industrial revolution from Great Britain to the European continent and beyond. The climactic consequence of this human-dominated increase in atmospheric CO$_{\mathrm{2}}$ has been suggested to define a geologic epoch, termed the ``Anthropocene.'' This could be a short term, relatively minor change in global climate, or an extreme deviation that lasts for thousands of years. In order to stabilize global temperatures, sharp reductions in CO$_{\mathrm{2}}$ emissions are required: an 80{\%} reduction beginning in 2050. U.S. emissions have declined sharply recently because of market conditions leading to the substitution of natural gas for coal for electricity generation. Whether this is the best use for this resource may be questioned, but it nevertheless reduces CO$_{\mathrm{2}}$ production by 67{\%} from a coal-fired power plant, well on the way to the 80{\%} reduction required for global temperature stabilization. Current methods for CO$_{\mathrm{2}}$ capture and storage are not cost effective, and have been slow (if not absent) to introduce at scale. This paper describes research into some potentially economically feasible approaches: cost-effective capture and storage of CO$_{\mathrm{2}}$ from injection of flue gas into subterranean methane-saturated aquifers at the surface; fuels from sunlight without CO$_{\mathrm{2}}$ production; and large-scale electrical energy storage for intermittent (and even constant) electricity generating sources. [Preview Abstract] |
Monday, March 18, 2013 8:36AM - 9:12AM |
A38.00002: High-Performance Electrocatalysts for Oxygen Reduction Derived from Polyaniline, Iron, and Cobalt Invited Speaker: Piotr Zelenay With the growing awareness that the use of platinum needs to either be greatly reduced or completely eliminated from the polymer electrolyte fuel cell (PEFC), non-precious metal catalysts for oxygen reduction reaction (ORR) have received lots of attention in recent years as a possible replacement of Pt and its alloys at the fuel cell cathode. A successful cathode catalyst must combine high ORR activity with good long-term stability -- a major challenge in the strongly acidic environment of the PEFC cathode. In response to the possibly greatest challenge of the PEFC technology, we have developed a family of non-precious metal ORR catalysts capable of minimizing the performance gap to platinum-based catalysts at a cost sustainable for high-power fuel cell applications, possibly including the automotive power plant. The approach utilizes polyaniline (PANI) as a precursor of a carbon-nitrogen template for high-temperature synthesis of catalysts in the presence of transition metals (Fe and/or Co). The most active materials in the group allow for the ORR to occur within ca. 60 mV of the potential delivered by a state-of-the-art carbon-supported Pt catalyst. A distinctive combination of (i) high ORR activity, (ii) unique performance stability for non-precious metal catalysts (more than 700 hours at a fuel cell voltage of 0.4 V), and (iii) excellent four-electron selectivity (H$_{\mathrm{2}}$O$_{\mathrm{2}}$ yield less than 1.0{\%}), make the leading catalyst in this group, PANI-FeCo(3:1), the best overall non-precious metal ORR catalyst studied to date. More recently, we have also focused on better understanding of the active ORR site via the use of advanced surface characterization techniques, such as nuclear resonance vibrational spectroscopy (NRVS), Monte Carlo pre-screening of possible active sites and more advanced DFT modeling of the most likely active-site structures. Combination of the experiment and theory is expected to aide in the rational design of the future ORR catalysts. [Preview Abstract] |
Monday, March 18, 2013 9:12AM - 9:24AM |
A38.00003: Modulated photocurrent spectroscopy of thin film solar cells Behrang Hamadani, John Roller, Panagiotis Kounavis, Nikolai Zhitenev, David Gundlach We used the modulated photocurrent spectroscopy technique based on sinusoidal excitation of high-powered LEDs to investigate the dynamic response of charge carrier transport in thin film solar cells based on CdTe. The impact of light bias, voltage bias and the temperature over a broad excitation frequency bandwidth were studied. The observed features of the data, including a photocurrent phase-lead and a phase-lag over different regions of the frequency spectrum, were explored in the context of an equivalent circuit model. Comparisons between the model's predicted performance and the measured data suggest that charge carrier recombination at the cell's back metal/semiconductor contact is the main source of photocurrent loss in the cells that were investigated by our group. [Preview Abstract] |
Monday, March 18, 2013 9:24AM - 9:36AM |
A38.00004: Ultrasensitive spectroscopy of ultrasmall quantum dots for energy conversion and lighting applications Lloyd Davis, Noah Orfield, Sandra Rosenthal Quantum dots typically have narrow spectra with a peak that tunes with their size but ultrasmall semiconductor nanocrystals of diameters less than a few nanometers have size-independent spectra and many other strikingly different properties. One especially interesting feature is that ultrasmall CdSe nanocrystals emit an almost pure white-light spectrum, which has great potential for solid-state lighting that yields excellent color rendering. To gain understanding of the photophysical properties and mechanisms for broadband emission, we have constructed a modular fluorescence microscope for ultrasensitive spectroscopy of individual nanoparticles. Using 400-nm wide-field excitation from a frequency-doubled Ti-Sapphire laser and a high-efficiency electron-multiplying CCD, we observe that single CdSe nanocrystals exhibit blinking and abrupt photobleaching, often after detection of only a few hundred photons. Moreover, spectrally dispersed imaging shows that each particle emits the entire broadband spectrum. We discuss mechanisms for homogeneous broadband emission and ongoing experiments in which the instrument is configured for scanning, confocal, two-channel, time-resolved single photon counting for studies of photon antibunching, emission lifetimes, and correlations between spectral regions. [Preview Abstract] |
Monday, March 18, 2013 9:36AM - 9:48AM |
A38.00005: Measuring Building Insulation Beth Parks Currently, the only way for homeowners to learn about the effectiveness of their home insulation is to hire an energy auditor. This difficulty deters homeowners from taking action to improve energy efficiency. In principle, measuring the temperature difference between a wall surface and the interior of a home is sufficient to determine the wall insulation, but in practice, temperature cycles from the heating system make a single measurement unreliable. I will describe a simple and inexpensive thermocouple-based device to measure this temperature difference and report results obtained by monitoring this temperature difference over multiple heating cycles in a range of buildings. [Preview Abstract] |
Monday, March 18, 2013 9:48AM - 10:00AM |
A38.00006: Optimized Electronic Transport Measurements in Titanium Oxide Jeffrey Lindemuth Titanium Oxide is a material with applications in thermal electric and solar cell applications. Measurement of electronic transport properties by standard methods, for instance Hall effect are made difficult by the low mobility of the material and coupled with the thermal electric properties of the material. Measurements of the resistivity and Hall effect are optimized to reduce the thermal electric effects on the measurement. The Hall measurement is further optimized, by use of AC field Hall method, to obtain reliable mobility values and carrier type determination. Optimization of the measurement includes noise reduction and repeatability of the measurement. Both constant temperature and room temperature measurements are used in the optimization method. [Preview Abstract] |
Monday, March 18, 2013 10:00AM - 10:12AM |
A38.00007: Neutron scattering studies of glassy Li$^{+}$ superionics Tom Heitmann, Leo Zella, Ali Zaidi, Munesh Rathore, Anshuman Dalvi, Saibal Mitra Two distinct neutron scattering techniques were implemented in the study of glassy superionic materials composed of a complex network of their interconnected sub-units: Li$_2$O, NH$_4$H$_2$PO$_2$, and Li$_2$SO$_4$. The use of disordered materials underlies an effort to promote Li$^{+}$ mobility, while suppressing e$^{-}$ conductivity, which makes them good candidates for use as electrolytes in lithium ion batteries. We present triple-axis spectrometer results of energy resolved vs. energy integrated neutron scattering that indicate the presence of a broad range of dynamic processes in the materials, rather than well-defined excitations. Additionally, we report on neutron diffraction data that demonstrates the formation of crystallites within the material upon annealing up to 450 $^{\circ}$C. Such crystallites hinder the performance of the materials as electrolytes, which is evident in thin film devices where heating is unavoidable during fabrication. [Preview Abstract] |
Monday, March 18, 2013 10:12AM - 10:24AM |
A38.00008: ABSTRACT WITHDRAWN |
Monday, March 18, 2013 10:24AM - 10:36AM |
A38.00009: Lithiation of UHV-prepared CoO Conversion Battery Materials Studied by XPS and TEM Ryan Thorpe, Sylvie Rangan, Robert Bartynski, Mahsa Sina, Frederic Cosandey Lithium-ion conversion batteries can store 2-3 times more energy than intercalation batteries by fully reducing their constituent divalent or trivalent transition metal compounds during discharge. A prototypical conversion compound is CoO, which follows the reaction 2Li$^{+}$ + 2e$^{-}$ + Co$^{(2+)}$O $\rightarrow$ 2Li$_{2}$O + Co$^{(0)}$ upon discharge. However, the cycling stability of conversion electrodes is poor, and capacity losses have prevented their implementation. To study the electronic and morphological changes that occur during the conversion reaction, we have grown 5 nm polycrystalline and epitaxial CoO films and exposed them to atomic Li in UHV to simulate cell discharge. Using XPS to monitor the valence state of Co and film stoichiometry, we find that at 25$^{\circ}$C this reaction is inhibited by the formation of a Li$_{2}$O$_{2}$ overlayer, which is a kinetic barrier for Li diffusion. This is alleviated by heating the film to 150$^{\circ}$C, thereby enhancing Li diffusivity through the overlayer and enabling complete reduction of the film. Epitaxial films are reduced with less Li than is required by polycrystalline films, suggesting the presence of channels through which Li is able to diffuse. In both cases, no cobalt phases other than CoO and Co are observed. [Preview Abstract] |
Monday, March 18, 2013 10:36AM - 10:48AM |
A38.00010: In situ Measurements of the Solid Electrolyte Interphase in Li-Ion Batteries Using Neutron Reflectometry Joseph Dura, Jeanette Owejan, Steven DeCaluwe, Jon Owejan The huge advantages of Li-ion batteries, i.e. high energy density and specific power are due not only to the low mass of Li, but also a direct result of the high operating voltage provided by the large electrochemical potential of Li. However, these advantages come at a cost, as all known electrolytes are unstable at these potentials. Li-ion batteries are only made possible by the solid electrolyte interphase, SEI, a passivation layer that forms from the decomposition products of certain electrolytes. Ideally the SEI offers sufficient electronic resistance when it has grown thick enough to stop additional electrolyte decomposition. However, slow continued SEI growth leads to capacity fade and increased cell resistance. Despite the SEI's critical significance, currently structural characterization is incomplete because of the reactive and delicate nature of the SEI and the electrolyte system in which it forms. Here we present the first in situ neutron reflectometry measurements of the SEI layer as function of potential in a working lithium half-cell. The SEI layer after 10 and 20 CV cycles is 4.0 and 4.5 nm, respectively, growing to 8.9 nm after a series of potentiostatic holds that approximates a charge/discharge cycle. Specified data sets show uniform mixing of SEI components. [Preview Abstract] |
Monday, March 18, 2013 10:48AM - 11:00AM |
A38.00011: Low temperature MRFM probe development and initial characterization of organic solar cells Mark Monti, Dimitri Alexson, Doran Smith We report on the construction of a Magnetic Resonance Force Microscope (MRFM) for organic solar cell characterization. Organic bulk-heterojunction solar cells (OSCs) consist of a blend of two organic semiconductors- an electron donating polymer and an electron accepting fullerene. The efficiency of blended OSCs is highly dependent on the phase separation between the donor and acceptor materials. MRFM offers a unique toolset to study OSCs with the potential to gain insight into the morphology of the buried heterostructure on an actual device. The MRFM probe will operate at 4K and up to 9T using force gradient detection of magnetic resonance via an ultra sensitive single crystal silicon cantilever. We plan on performing NMR spectroscopy on OSCs using a shuttling technique whereby the sample is shuttled far from the gradient magnetic particle during the encoding portion of the NMR RF pulses. We will present on the status of the probe development and on our initial experiments on organic solar cells. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700