Energy-related Sciences Research Articles

Assignment of Terahertz Modes in Hydroquinone Clathrates

Hydroquinone (HQ) and its clathrate are materials of growing interests, due to their promising applications in energy related science and industries. Recently, many studies have been performed to understand the properties of these materials. Terahertz (THz) spectroscopy is a powerful tool for studying the properties of these materials by non-destructively probing their low-energy (meV) dynamics. Although terahertz spectra of HQ and its clathrates have been measured, a report on the correspondence between THz spectra and low frequency dynamics is still lacking. In this paper, we measure the temperature-dependent THz spectra of both α-HQ (the non-clathrate form) and β-HQ clathrate, with Ar and CO2 as guest species. We also perform density functional theory (DFT) simulations on these materials, in order to assign the spectral features. We find an excellent match between the experimental and the DFT calculated spectra. Using the simulation result, we build connections between the THz spectra and the atomic motions in these materials. In addition, we also perform DFT simulations on β-HQ-He, β-HQ-Ne, and β-HQ-Kr to study the patterns in the change of THz spectra as the guest species changes.

“Hands-on” plus “inquiry”? Effects of withholding answers coupled with physical manipulations on students' learning of energy-related science concepts

A recent discussion on science teaching has been focusing on questions of whether it is necessary to withhold answers from learners until inquiry activities are completed and whether learners develop high-level science learning when they are physically involved in scientific investigations. To contribute to this topic, the present study examined the effects of withholding answers from learners coupled with involving them in physical manipulations on their learning of energy transfer in three domains, knowing, reasoning, and applying. The study compared students' learning outcomes in the hands-on inquiry condition that incorporated the two instructional elements, with learning in the explicit investigation condition that only involved learners in manipulations, and in direct instruction condition that excluded the two instructional elements. The results showed that the instructional conditions affected students' learning of energy transfer in knowing and reasoning, but not in applying. After controlling for students' prior knowledge, participants in the hands-on inquiry condition gained less class content and demonstrated a lower ability of reasoning than those in the direct instruction condition. Students did not differ in their ability to apply the learned content to real-life situations across conditions.

Crystalline Porous Materials and Their Applications in Electrochemical Energy Storage Devices: Lithium Batteries and Li-Sulfur Batteries

The development of new electrochemically active materials towards the application of battery electrodes is still one of the most intriguing topics in energy-related science. A good electrode material requires not only a large energy storage density, but also high permeability to electrolytes and robustness during the electrochemical process. From the perspective of synthetic material science, we chose highly crystalline porous materials, including metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs) as the target of research. The crystallinity of materials guaranteed the stability upon the electrochemcial treatment, while the porosity allowed the penetration of electrolytes and a high mobility of ions in the materials. Towards Li-ion batteries, we could achieve the electron accepting ability on both metal cation clusters and organic linkers of MOFs with proper design strategies and a total capacity that is comparable with major commercialized batteries has been obtained. A series of physical measurements were performed and resulted an insight to the mechanism of the electrochemical processes, hence the discovery of a "bipolar charging" mechanism that has not been observed for traditional Li-ion batteries. Such mechanism utilized the insertion of both Li-ions and anions from the electrolyte, which alternates the doping feature and the ionic conductivity of MOFs in electrochemical steps. We also examined the potential of these porous materials as the substrate of sulfur in the cathode of Li-S batteries, as they can easily separate sulfur into nanoparticles through a simple adsorption approach. We performed studies on a series of isoreticular MOFs, UiO-66-68, which adopt same structural topology and the only difference is pore size and pore volume. The C-rate dependent electrochemcial behavior of sulfur impregnated MOFs were analyzed and suggested the importance of pore size. Furthermore, we prepared MOFs and COFs with functionalized sulfur binding groups, and the linkage between the sulfur and porous frameworks generated a new type of polymer, namely MOF/COF-graft-polysulfides. These new type of polymers were applied as the cathode materials of Li-S batteries, and the binding groups sucessfully increased the cyclic performance of Li-S batteries referencing with non-functionalized MOFs/COFs.

ChemInform Abstract: Covalent Multi‐component Systems of Polyoxometalates and Metal Complexes: Toward Multi‐functional Organic‐inorganic Hybrids in Molecular and Material Sciences

AbstractReview: 138 refs.

A high resolution and large solid angle x-ray Raman spectroscopy end-station at the Stanford Synchrotron Radiation Lightsource.

We present a new x-ray Raman spectroscopy end-station recently developed, installed, and operated at the Stanford Synchrotron Radiation Lightsource. The end-station is located at wiggler beamline 6-2 equipped with two monochromators-Si(111) and Si(311) as well as collimating and focusing optics. It consists of two multi-crystal Johann type spectrometers arranged on intersecting Rowland circles of 1 m diameter. The first one, positioned at the forward scattering angles (low-q), consists of 40 spherically bent and diced Si(110) crystals with 100 mm diameters providing about 1.9% of 4π sr solid angle of detection. When operated in the (440) order in combination with the Si (311) monochromator, an overall energy resolution of 270 meV is obtained at 6462.20 eV. The second spectrometer, consisting of 14 spherically bent Si(110) crystal analyzers (not diced), is positioned at the backward scattering angles (high-q) enabling the study of non-dipole transitions. The solid angle of this spectrometer is about 0.9% of 4π sr, with a combined energy resolution of 600 meV using the Si (311) monochromator. These features exceed the specifications of currently existing relevant instrumentation, opening new opportunities for the routine application of this photon-in/photon-out hard x-ray technique to emerging research in multidisciplinary scientific fields, such as energy-related sciences, material sciences, physical chemistry, etc.

New ambient pressure photoemission endstation at Advanced Light Source beamline 9.3.2

During the past decade, the application of ambient pressure photoemission spectroscopy (APPES) has been recognized as an important in situ tool to study environmental and materials science, energy related science, and many other fields. Several APPES endstations are currently under planning or development at the USA and international light sources, which will lead to a rapid expansion of this technique. The present work describes the design and performance of a new APPES instrument at the Advanced Light Source beamline 9.3.2 at Lawrence Berkeley National Laboratory. This new instrument, Scienta R4000 HiPP, is a result of collaboration between Advanced Light Source and its industrial partner VG-Scienta. The R4000 HiPP provides superior electron transmission as well as spectromicroscopy modes with 16 microm spatial resolution in one dimension and angle-resolved modes with simulated 0.5 degrees angular resolution at 24 degrees acceptance. Under maximum transmission mode, the electron detection efficiency is more than an order of magnitude better than the previous endstation at beamline 9.3.2. Herein we describe the design and performance of the system, which has been utilized to record spectra above 2 mbar.

Congress Moves To Reorganize Department of Energy Labs

Two bills that would transform the missions and practices of the Department of Energy's research laboratories are moving forward in both branches of Congress. Each of the two is crafted to improve cooperative research between DOE and private industry, but the House bill goes further by making fundamental changes in lab administration. H.R. 1432 provides a clear statement of purpose for the labs. The eight missions outlined in the bill are as follows: Enhance the nation's understanding of energy production and use, with a goal of reducing reliance on imported sources of fuels; Advance nuclear science and technology for national security purposes; Assist with dismantlement of nuclear weapons and work to curb nuclear arms proliferation; Conduct fundamental research in energy-related science and technology; Assist in development of technologies for disposal of hazardous wastes, particularly nuclear waste; Work with private industry to develop generic green technologies; Conduct technology-transfer activities; and Work to improve the quality of science, math, and engineering education in the U.S.