News Article | May 11, 2017
Man-made pollution in eastern China's cities worsens when less dust blows in from the Gobi Desert, according to a new study published May 11 in Nature Communications. Yes, you read that correctly: When less natural dust blows in, the air quality for millions of people worsens. That's because dust plays an important role in determining the air temperatures and thereby promoting winds to blow away man-made pollution. Less dust means the air stagnates, with man-made pollution becoming more concentrated and sticking around longer. The scientists found that reduced dust causes a 13 percent increase in man-made pollution over eastern China during the winter. Researchers say the broader question of how natural dust and man-made pollution interact is an important one for people across the globe, not just China. Many of the same forces that ease or worsen pollution in China are at play in many areas around the globe, including several cities in the United States. The paradoxical finding -- that more natural dust in the air improves air quality -- comes from a team of researchers from the Department of Energy's Pacific Northwest National Laboratory and Scripps Institution of Oceanography at the University of California at San Diego. Post-doctoral researcher Yang Yang of PNNL is first author of the paper, and Lynn Russell of Scripps is the corresponding author. In computer models together with historical data, the team found that reduced natural dust transported from the Gobi Desert in central and northern China translates to increased man-made air pollution in highly populated eastern China. The reason is that natural dust particles in the air help deflect sunlight. Fewer dust particles translates to a warmer-than-usual land surface and cooler-than-usual water. That reduces the temperature differential in winter between sea and the land, resulting in weaker winds -- and increased air stagnation. As a result, during the winter monsoon season, eastern China experiences weaker winds when there's less natural dust in the air. It's nothing a person would notice -- a reduction barely more than one-tenth of one mile per hour -- but on a large scale over an entire region, such a seemingly minor change has a profound effect on climate and air quality. "This is one of the first times we've really looked at the interactions between natural dust, wind, and anthropogenic pollution," said Yang. "It turns out that dust plays an important role in determining the quality of the air for many people in eastern China." The modeling results match observational data from dozen of sites in eastern China. The team found that two to three days after winds had brought dust into the region from western China, the air was cleaner than before the dust arrived. The researchers say man-made pollution is still the core of air pollution in cities like Beijing in eastern China but that it's important to understand the role of natural dust particles.
Clemson University, Lawrence Berkeley National Laboratory and Pacific Northwest National Laboratory | Date: 2016-11-23
A liquid sampling, atmospheric pressure, glow discharge (LS-APGD) device as well as systems that incorporate the device and methods for using the device and systems are described. The LS-APGD includes a hollow capillary for delivering an electrolyte solution to a glow discharge space. The device also includes a counter electrode in the form of a second hollow capillary that can deliver the analyte into the glow discharge space. A voltage across the electrolyte solution and the counter electrode creates the microplasma within the glow discharge space that interacts with the analyte to move it to a higher energy state (vaporization, excitation, and/or ionization of the analyte).
Luo L.,Pacific Northwest National Laboratory
Nature Nanotechnology | Year: 2017
The performances of a Li–O2 battery depend on a complex interplay between the reaction mechanism at the cathode, the chemical structure and the morphology of the reaction products, and their spatial and temporal evolution; all parameters that, in turn, are dependent on the choice of the electrolyte. In an aprotic cell, for example, the discharge product, Li2O2, forms through a combination of solution and surface chemistries that results in the formation of a baffling toroidal morphology. In a solid electrolyte, neither the reaction mechanism at the cathode nor the nature of the reaction product is known. Here we report the full-cycle reaction pathway for Li–O2 batteries and show how this correlates with the morphology of the reaction products. Using aberration-corrected environmental transmission electron microscopy (TEM) under an oxygen environment, we image the product morphology evolution on a carbon nanotube (CNT) cathode of a working solid-state Li–O2 nanobattery and correlate these features with the electrochemical reaction at the electrode. We find that the oxygen-reduction reaction (ORR) on CNTs initially produces LiO2, which subsequently disproportionates into Li2O2 and O2. The release of O2 creates a hollow nanostructure with Li2O outer-shell and Li2O2 inner-shell surfaces. Our findings show that, in general, the way the released O2 is accommodated is linked to lithium-ion diffusion and electron-transport paths across both spatial and temporal scales; in turn, this interplay governs the morphology of the discharging/charging products in Li–O2 cells. © 2017 Nature Publishing Group
Lu N.,Pacific Northwest National Laboratory
IEEE Transactions on Smart Grid | Year: 2012
This paper investigates the potential of providing intra-hour load balancing services using aggregated heating, ventilating, and air-conditioning (HVAC) loads. A directload control algorithm is presented. A temperature-priority-list method is used to dispatch the HVAC loads optimally to maintain customer-desired indoor temperatures and load diversity. Realistic intra-hour load balancing signals are used to evaluate the operational characteristics of the HVAC load under different outdoor temperature profiles and different indoor temperature settings. The number of HVAC units needed is also investigated. Modeling results suggest that the number of HVAC units needed to provide a ±1-MW load balancing service 24 hours a day varies significantly with baseline settings, high and low temperature settings, and outdoor temperatures. The results demonstrate that the intra-hour load balancing service provided by HVAC loads meets the performance requirements and can become a major source of revenue for load-serving entities where the two-way communication smart grid infrastructure enables direct load control over the HVAC loads. © 2010-2012 IEEE.
Henderson M.A.,Pacific Northwest National Laboratory
Surface Science Reports | Year: 2011
The field of surface science provides a unique approach to understanding bulk, surface and interfacial phenomena occurring during TiO2 photocatalysis. This review highlights, from a surface science perspective, recent literature that provides molecular-level insights into photon-initiated events occurring at TiO2 surfaces. Seven key scientific issues are identified in the organization of this review. These are: (1) photon absorption, (2) charge transport and trapping, (3) electron transfer dynamics, (4) the adsorbed state, (5) mechanisms, (6) poisons and promoters, and (7) phase and form. This review ends with a brief examination of several chemical processes (such as water splitting) in which TiO2 photocatalysis has made significant contributions in the literature. © 2011 Elsevier B.V. All rights reserved.
Chambers S.A.,Pacific Northwest National Laboratory
Advanced Materials | Year: 2010
The detailed science and technology of crystalline oxide film growth using vacuum methods is reviewed and discussed with an eye toward gaining fundamental insights into the relationships between growth process and parameters, film and interface structure and composition, and electronic, magnetic and photochemical properties. The topic is approached first from a comparative point of view based on the most widely used growth methods, and then on the basis of specific material systems that have generated very high levels of interest. Emphasis is placed on the wide diversity of structural, electronic, optical and magnetic properties exhibited by oxides, and the fascinating results that this diversity of properties can produce when combined with the degrees of freedom afforded by heteroepitaxy. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA.
Liu J.,Pacific Northwest National Laboratory
Advanced Functional Materials | Year: 2013
The Special Issue of Advanced Functional Material 2013 on Energy Storage provides a comprehensive and balanced view of materials chemistry and materials challenges for a wide range of technologies and applications from transportation electrification to the utility grid. The paper by Liu and co-researchers gives a detailed analysis of the energy storage landscape and status of the materials and technologies, which is followed by review articles on important technologies and featured research articles that include the latest advances in leading groups from the international community. Papers by Perez and colleagues and Byon and colleagues report new results on methods to produce novel carbon architectures which have good potential for anodes in Li-ion batteries and electrodes for supercapacitors. This Special Issue also includes one paper by Lee and researchers on composite gel electrolytes with Li powders as the anode.
Dubois D.L.,Pacific Northwest National Laboratory
Inorganic Chemistry | Year: 2014
Molecular electrocatalysts can play an important role in energy storage and utilization reactions needed for intermittent renewable energy sources. This manuscript describes three general themes that our laboratories have found useful in the development of molecular electrocatalysts for reduction of CO 2 to CO and for H2 oxidation and production. The first theme involves a conceptual partitioning of catalysts into first, second, and outer coordination spheres. This is illustrated with the design of electrocatalysts for CO2 reduction to CO using first and second coordination spheres and for H2 production catalysts using all three coordination spheres. The second theme focuses on the development of thermodynamic models that can be used to design catalysts to avoid high- and low-energy intermediates. In this research, new approaches to the measurement of thermodynamic hydride donor and acceptor abilities of transition-metal complexes were developed. Combining this information with other thermodynamic information such as pKa values and redox potentials led to more complete thermodynamic descriptions of transition-metal hydride, dihydride, and related species. Relationships extracted from this information were then used to develop models that are powerful tools for predicting and understanding the relative free energies of intermediates in catalytic reactions. The third theme is control of proton movement during electrochemical fuel generation and utilization reactions. This research involves the incorporation of pendant amines in the second coordination sphere that can facilitate H-H bond heterolysis and heteroformation, intra- and intermolecular proton-transfer steps, and coupling of proton- and electron-transfer steps. Studies also indicate an important role for the outer coordination sphere in the delivery of protons to the second coordination sphere. Understanding these proton-transfer reactions and their associated energy barriers is key to the design of faster and more efficient molecular electrocatalysts for energy storage. © 2014 American Chemical Society.
Gao F.,Pacific Northwest National Laboratory |
Goodman D.W.,Texas A&M University
Chemical Society Reviews | Year: 2012
Pd-Au bimetallic catalysts often display enhanced catalytic activities and selectivities compared with Pd-alone catalysts. This enhancement is often caused by two alloy effects, i.e., ensemble and ligand effects. The ensemble effect is a dilution of surface Pd by Au. With increasing surface Au coverage, contiguous Pd ensembles disappear and isolated Pd ensembles form. For certain reactions, for example vinyl acetate synthesis, this effect is responsible for reaction rate enhancement via the formation of highly active surface sites, e.g., isolated Pd pairs. The disappearance of contiguous Pd ensembles also switches off side reactions catalyzed by these sites. This explains the selectivity increase of certain reactions, for example direct H 2O 2 synthesis. The ligand effects are electronic perturbation of Pd by Au. Via direct charge transfer or by affecting bond lengths, the ligand effects cause the Pd d band to be more filled, moving the d-band center away from the Fermi level. Both changes make Pd more "atomic like" therefore binding reactants and products more weakly. For certain reactions, this eliminates a so-called "self-poisoning" effect and enhances activity/selectivity. © 2012 The Royal Society of Chemistry.
Bullock R.M.,Pacific Northwest National Laboratory
Science | Year: 2013
Iron- or cobalt-based catalysts have outperformed traditional precious metal catalysts in several hydrogenation reactions.