{"429491":{"#nid":"429491","#data":{"type":"news","title":"Sol-gel Capacitor Dielectric Offers Record-high Energy Storage","body":[{"value":"\u003Cp\u003EUsing a hybrid silica sol-gel material and self-assembled monolayers of a common fatty acid, researchers have developed a new capacitor dielectric material that provides an electrical energy storage capacity rivaling certain batteries, with both a high energy density and high power density.\u003C\/p\u003E\u003Cp\u003EIf the material can be scaled up from laboratory samples, devices made from it could surpass traditional electrolytic capacitors for applications in electromagnetic propulsion, electric vehicles and defibrillators. Capacitors often complement batteries in these applications because they can provide large amounts of current quickly.\u003C\/p\u003E\u003Cp\u003EThe new material is composed of a silica sol-gel thin film containing polar groups linked to the silicon atoms and a nanoscale self-assembled monolayer of an octylphosphonic acid, which provides insulating properties. The bilayer structure blocks the injection of electrons into the sol-gel material, providing low leakage current, high breakdown strength and high energy extraction efficiency.\u003C\/p\u003E\u003Cp\u003E\u201cSol-gels with organic groups are well known and fatty acids such as phosphonic acids are well known,\u201d noted \u003Ca href=\u0022http:\/\/www.chemistry.gatech.edu\/people\/Perry\/Joseph%20W.\u0022\u003EJoseph Perry\u003C\/a\u003E, a professor in the \u003Ca href=\u0022http:\/\/www.chemistry.gatech.edu\/\u0022\u003ESchool of Chemistry and Biochemistry\u003C\/a\u003E at the Georgia Institute of Technology. \u201cBut to the best of our knowledge, this is the first time these two types of materials have been combined into high-density energy storage devices.\u201d\u003C\/p\u003E\u003Cp\u003EThe research, supported by the Office of Naval Research and the Air Force Office of Scientific Research, was reported July 14 in the journal \u003Cem\u003EAdvanced Energy Materials\u003C\/em\u003E.\u003C\/p\u003E\u003Cp\u003EThe need for efficient, high-performance materials for electrical energy storage has been growing along with the ever-increasing demand for electrical energy in mobile applications. Dielectric materials can provide fast charge and discharge response, high energy storage, and power conditioning for defense, medical and commercial applications. But it has been challenging to find a single dielectric material able to maximize permittivity, breakdown strength, energy density and energy extraction efficiency.\u003C\/p\u003E\u003Cp\u003EPerry and colleagues in Georgia Tech\u2019s \u003Ca href=\u0022http:\/\/www.cope.gatech.edu\/\u0022\u003ECenter for Organic Photonics and Electronics\u003C\/a\u003E (COPE) had been working on other capacitor materials to meet these demands, but were not satisfied with the progress. The hybrid sol-gel materials had shown potential for efficient dielectric energy storage because of their high orientational polarization under an electric field, so the group decided to pursue these materials for the new capacitor applications.\u003C\/p\u003E\u003Cp\u003EUsing an aluminized mylar film coated with the hybrid sol-gel capacitor material, they showed that the capacitor could be rolled and re-rolled several times while maintaining high energy density, demonstrating its flexibility. But they were still seeing high current leakage. To address that, they deposited a nanoscale self-assembled monolayer of n-octylphosphonic acid on top of the hybrid sol-gel. Less than a nanometer thick, the monolayer serves as an insulating layer.\u003C\/p\u003E\u003Cp\u003E\u201cOur silica sol-gel is a hybrid material because it has polar organic groups attached to the silica framework that gives the sol-gel a high dielectric constant, and in our bilayer dielectric, the n-octylphosphonic acid groups are inserted between the sol-gel layer and the top aluminum layer to block charge injection into the sol-gel,\u201d Perry explained. \u201cIt\u2019s really a bilayer hybrid material that takes the best of both reorientation polarization and approaches for reducing injection and improving energy extraction.\u201d\u003C\/p\u003E\u003Cp\u003EIn their structures, the researchers demonstrated maximum extractable energy densities up to 40 joules per cubic centimeter, an energy extraction efficiency of 72 percent at a field strength of 830 volts per micron, and a power density of 520 watts per cubic centimeter. The performance exceeds that of conventional electrolytic capacitors and thin-film lithium ion batteries, though it doesn\u2019t match the lithium ion battery formats commonly used in electronic devices and vehicles.\u003C\/p\u003E\u003Cp\u003E\u201cThis is the first time I\u2019ve seen a capacitor beat a battery on energy density,\u201d said Perry. \u201cThe combination of high energy density and high power density is uncommon in the capacitor world.\u201d\u003C\/p\u003E\u003Cp\u003EResearchers in Perry\u2019s lab have been making arrays of small sol-gel capacitors in the lab to gather information about the material\u2019s performance. The devices are made on small substrates about an inch square.\u003C\/p\u003E\u003Cp\u003E\u201cWhat we see when we apply an electric field is that the polarization response \u2013 which measures how much the polar groups line up in a stable way with the field \u2013 behaves in a linear way,\u201d said Perry. \u201cThis is what you want to see in a capacitor dielectric material.\u201d\u003C\/p\u003E\u003Cp\u003EThe next step will be to scale up the materials to see if the attractive properties transfer to larger devices. If that is successful, Perry expects to commercialize the material through a startup company or SBIR project.\u003C\/p\u003E\u003Cp\u003E\u201cThe simplicity of fully solution-based processes for our dielectric material system provides potential for facile scale-up and fabrication on flexible platforms,\u201d the authors wrote in their paper. \u201cThis work emphasizes the importance of controlling the electrode-dielectric interface to maximize the performance of dielectric materials for energy storage application.\u201d\u003C\/p\u003E\u003Cp\u003EIn addition to Perry, the research team included Yunsang Kim, Mohanalingam Kathaperumal and Vincent Chen from the Georgia Tech School of Chemistry and Biochemistry; Yohan Park from the Georgia Tech School of Materials Science and Engineering; Canek Fuentes-Hernandez and Bernard Kippelen from the Georgia Tech School of Electrical and Computer Engineering, and Ming-Hen Pan from the Naval Research Laboratory.\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThis research was supported by the Office of Naval Research Dielectric Films Program (Grant N000141110462) and U.S. Air Force Office of Scientific Research, BioPAINTS MURI Program (Grant FA9550-09-0669). The content of this article is solely the responsibility of the authors and does not necessarily represent the official views of the sponsoring agencies.\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ECITATION\u003C\/strong\u003E: Yunsang Kim, et al., \u201cBilayer Structure with Ultra-high Energy\/Power Density Using Hybrid Sol-Gel Dielectric and Charge Blocking Monolayer, (Advanced Energy Materials, 2015). \u003Ca href=\u0022http:\/\/www.dx.doi.org\/10.1002\/aenm.201500767\u0022\u003Ehttp:\/\/www.dx.doi.org\/10.1002\/aenm.201500767\u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EResearch News\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EGeorgia Institute of Technology\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003E177 North Avenue\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EAtlanta, Georgia 30332-0181 USA\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EMedia Relations Contact\u003C\/strong\u003E: John Toon (\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E) (404-894-6986)\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EUsing a hybrid silica sol-gel material and self-assembled monolayers of a common fatty acid, researchers have developed a new capacitor dielectric material that provides an electrical energy storage capacity rivaling certain batteries, with both a high energy density and high power density.\u0026nbsp;\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Researchers have developed a new capacitor dielectric material that provides an electrical energy storage capacity rivaling certain batteries."}],"uid":"27303","created_gmt":"2015-07-29 20:50:05","changed_gmt":"2016-10-08 03:19:19","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2015-07-29T00:00:00-04:00","iso_date":"2015-07-29T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"429461":{"id":"429461","type":"image","title":"Sol-gel solution","body":null,"created":"1449254358","gmt_created":"2015-12-04 18:39:18","changed":"1475895167","gmt_changed":"2016-10-08 02:52:47"},"429441":{"id":"429441","type":"image","title":"Sol-gel materials","body":null,"created":"1449254358","gmt_created":"2015-12-04 18:39:18","changed":"1475895167","gmt_changed":"2016-10-08 02:52:47"},"429421":{"id":"429421","type":"image","title":"Testing sol-gel materials","body":null,"created":"1449254358","gmt_created":"2015-12-04 18:39:18","changed":"1475895167","gmt_changed":"2016-10-08 02:52:47"},"429451":{"id":"429451","type":"image","title":"Sol-gel samples","body":null,"created":"1449254358","gmt_created":"2015-12-04 18:39:18","changed":"1475895167","gmt_changed":"2016-10-08 02:52:47"},"429481":{"id":"429481","type":"image","title":"Perry research group","body":null,"created":"1449254358","gmt_created":"2015-12-04 18:39:18","changed":"1475895169","gmt_changed":"2016-10-08 02:52:49"}},"media_ids":["429461","429441","429421","429451","429481"],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"141","name":"Chemistry and Chemical Engineering"},{"id":"144","name":"Energy"},{"id":"149","name":"Nanotechnology and Nanoscience"},{"id":"135","name":"Research"}],"keywords":[{"id":"7564","name":"capacitor"},{"id":"136861","name":"dielectric"},{"id":"213","name":"energy"},{"id":"479","name":"Green Buzz"},{"id":"7435","name":"material"},{"id":"169747","name":"sol-gel"}],"core_research_areas":[{"id":"39531","name":"Energy and Sustainable Infrastructure"},{"id":"39471","name":"Materials"},{"id":"39491","name":"Renewable Bioproducts"}],"news_room_topics":[{"id":"71881","name":"Science and Technology"}],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EJohn Toon\u003C\/p\u003E\u003Cp\u003EResearch News\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003E404-894-6986\u003C\/p\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}},"428411":{"#nid":"428411","#data":{"type":"news","title":"Smart Hydrogel Coating Creates \u201cStick-slip\u201d Control of Capillary Action","body":[{"value":"\u003Cp\u003ECoating the inside of glass microtubes with a polymer hydrogel material dramatically alters the way capillary forces draw water into the tiny structures, researchers have found. The discovery could provide a new way to control microfluidic systems, including popular lab-on-a-chip devices.\u003C\/p\u003E\u003Cp\u003ECapillary action draws water and other liquids into confined spaces such as tubes, straws, wicks and paper towels, and the flow rate can be predicted using a simple hydrodynamic analysis. But a chance observation by researchers at the Georgia Institute of Technology will cause a recalculation of those predictions for conditions in which hydrogel films line the tubes carrying water-based liquids.\u003C\/p\u003E\u003Cp\u003E\u201cRather than moving according to conventional expectations, water-based liquids slip to a new location in the tube, get stuck, then slip again \u2013 and the process repeats over and over again,\u201d explained \u003Ca href=\u0022http:\/\/www.me.gatech.edu\/faculty\/fedorov\u0022\u003EAndrei Fedorov\u003C\/a\u003E, a professor in the \u003Ca href=\u0022http:\/\/www.me.gatech.edu\/\u0022\u003EGeorge W. Woodruff School of Mechanical Engineering \u003C\/a\u003Eat Georgia Tech. \u201cInstead of filling the tube with a rate of liquid penetration that slows with time, the water propagates at a nearly constant speed into the hydrogel-coated capillary. This was very different from what we had expected.\u201d\u003C\/p\u003E\u003Cp\u003EThe findings resulted from research sponsored by the Air Force Office of Scientific Research (AFOSR) through the BIONIC center at Georgia Tech, and were reported earlier this month in the journal \u003Cem\u003ESoft Matter\u003C\/em\u003E.\u003C\/p\u003E\u003Cp\u003EWhen the opening of a thin glass tube is exposed to a droplet of water, the liquid begins to flow into the tube, pulled by a combination of surface tension in the liquid and adhesion between the liquid and the walls of the tube. Leading the way is a meniscus, a curved surface of the water at the leading edge of the water column. An ordinary borosilicate glass tube fills by capillary action at a gradually decreasing rate with the speed of meniscus propagation slowing as a square root of time.\u003C\/p\u003E\u003Cp\u003EBut when the inside of a tube is coated with a very thin layer of poly(N-isopropylacrylamide), a so-called \u201csmart\u201d polymer (PNIPAM), everything changes. Water entering a tube coated on the inside with a dry hydrogel film must first wet the film and allow it to swell before it can proceed farther into the tube. The wetting and swelling take place not continuously, but with discrete steps in which the water meniscus first sticks and its motion remains arrested while the polymer layer locally deforms. The meniscus then rapidly slides for a short distance before the process repeats. This \u201cstick-slip\u201d process forces the water to move into the tube in a step-by-step motion.\u003C\/p\u003E\u003Cp\u003EThe flow rate measured by the researchers in the coated tube is three orders of magnitude less than the flow rate in an uncoated tube. A linear equation describes the time dependence of the filling process instead of a classical quadratic equation which describes filling of an uncoated tube.\u003C\/p\u003E\u003Cp\u003E\u201cInstead of filling the capillary in a hundredth of a second, it might take tens of seconds to fill the same capillary,\u201d said Fedorov. \u201cThough there is some swelling of the hydrogel upon contact with water, the change in the tube diameter is negligible due to the small thickness of the hydrogel layer. This is why we were so surprised when we first observed such a dramatic slow-down of the filing process in our experiments.\u201d\u003C\/p\u003E\u003Cp\u003EThe researchers \u2013 who included graduate students James Silva, Drew Loney and Ren Geryak and senior research engineer Peter Kottke \u2013 tried the experiment again using glycerol, a liquid that is not absorbed by the hydrogel. With glycerol, the capillary action proceeded through the hydrogel-coated microtube as with an uncoated tube in agreement with conventional theory. After using high-resolution optical visualization to study the meniscus propagation while the polymer swelled, the researchers realized they could put this previously-unknown behavior to good use.\u003C\/p\u003E\u003Cp\u003EWater absorption by the hydrogels occurs only when the materials remain below a specific transition temperature. When heated above that temperature, the materials no longer absorb water, eliminating the \u201cstick-slip\u201d phenomenon in the microtubes and allowing them to behave like ordinary tubes.\u003C\/p\u003E\u003Cp\u003EThis ability to turn the stick-slip behavior on and off with temperature could provide a new way to control the flow of water-based liquid in microfluidic devices, including labs-on-a-chip. The transition temperature can be controlled by varying the chemical composition of the hydrogel.\u003C\/p\u003E\u003Cp\u003E\u201cBy locally heating or cooling the polymer inside a microfluidic chamber, you can either speed up the filling process or slow it down,\u201d Fedorov said. \u201cThe time it takes for the liquid to travel the same distance can be varied up to three orders of magnitude. That would allow precise control of fluid flow on demand using external stimuli to change polymer film behavior.\u201d\u003C\/p\u003E\u003Cp\u003EThe heating or cooling could be done locally with lasers, tiny heaters, or thermoelectric devices placed at specific locations in the microfluidic devices.\u003C\/p\u003E\u003Cp\u003EThat could allow precise timing of reactions in microfluidic devices by controlling the rate of reactant delivery and product removal, or allow a sequence of fast and slow reactions to occur. Another important application could be controlled drug release in which the desired rate of molecule delivery could be dynamically tuned over time to achieve the optimal therapeutic outcome.\u003C\/p\u003E\u003Cp\u003EIn future work, Fedorov and his team hope to learn more about the physics of the hydrogel-modified capillaries and study capillary flow using partially-transparent microtubes. They also want to explore other \u201csmart\u201d polymers which change the flow rate in response to different stimuli, including the changing pH of the liquid, exposure to electromagnetic radiation, or the induction of mechanical stress \u2013 all of which can change the properties of a particular hydrogel designed to be responsive to those triggers.\u003C\/p\u003E\u003Cp\u003E\u201cThese experimental and theoretical results provide a new conceptual framework for liquid motion confined by soft, dynamically evolving polymer interfaces in which the system creates an energy barrier to further motion through elasto-capillary deformation, and then lowers the barrier through diffusive softening,\u201d the paper\u2019s authors wrote. \u201cThis insight has implications for optimal design of microfluidic and lab-on-a-chip devices based on stimuli-responsive smart polymers.\u201d\u003C\/p\u003E\u003Cp\u003EIn addition to those already mentioned, the research team included Professor Vladimir Tsukruk from the Georgia Tech School of Materials Science and Engineering and Rajesh Naik, Biotechnology Lead and Tech Advisor of the Nanostructured and Biological Materials Branch of the Air Force Research Laboratory (AFRL).\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThis research was supported by the Air Force Office of Scientific Research BIONIC Center through awards FA9550-09-1-0162 and FA9550-14-1-0269, AFOSR award FA-9550-14-1-0015, and by Georgia Tech\u2019s Renewable Bioproducts Institute Fellowship. The content is solely the responsibility of the authors and does not necessarily represent the official views of the sponsors.\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ECITATION\u003C\/strong\u003E: J.E. Silva, et al., \u201cStick-Slip Water Penetration into Capillaries Coated with Swelling Hydrogel,\u201d (Soft Matter, 11, pp. 5933-5939, 2015).\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EResearch News\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EGeorgia Institute of Technology\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003E177 North Avenue\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EAtlanta, Georgia 30332-0181\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EMedia Relations Contact\u003C\/strong\u003E: John Toon (\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E) or (404-894-6986)\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003ECoating the inside of glass microtubes with a polymer hydrogel material dramatically alters the way capillary forces draw water into the tiny structures, researchers have found. The discovery could provide a new way to control microfluidic systems, including popular lab-on-a-chip devices.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Capillary action inside glass tubes coated with a hydrogel behaves in unexpected ways."}],"uid":"27303","created_gmt":"2015-07-25 10:59:58","changed_gmt":"2016-10-08 03:19:15","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2015-07-27T00:00:00-04:00","iso_date":"2015-07-27T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"428381":{"id":"428381","type":"image","title":"Capillary action in coated tube","body":null,"created":"1449254358","gmt_created":"2015-12-04 18:39:18","changed":"1475895167","gmt_changed":"2016-10-08 02:52:47","alt":"Capillary action in coated tube","file":{"fid":"202819","name":"capillary-action1791.jpg","image_path":"\/sites\/default\/files\/images\/capillary-action1791_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/capillary-action1791_0.jpg","mime":"image\/jpeg","size":1673866,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/capillary-action1791_0.jpg?itok=PUJWawsK"}},"428391":{"id":"428391","type":"image","title":"Studying capillary action in coated microtubes","body":null,"created":"1449254358","gmt_created":"2015-12-04 18:39:18","changed":"1475895167","gmt_changed":"2016-10-08 02:52:47","alt":"Studying capillary action in coated microtubes","file":{"fid":"202820","name":"capillary-action35.jpg","image_path":"\/sites\/default\/files\/images\/capillary-action35_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/capillary-action35_0.jpg","mime":"image\/jpeg","size":1434489,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/capillary-action35_0.jpg?itok=QNvAnNpB"}},"428401":{"id":"428401","type":"image","title":"Studying capillary action in coated microtubes2","body":null,"created":"1449254358","gmt_created":"2015-12-04 18:39:18","changed":"1475895167","gmt_changed":"2016-10-08 02:52:47","alt":"Studying capillary action in coated microtubes2","file":{"fid":"202821","name":"capillary-action60.jpg","image_path":"\/sites\/default\/files\/images\/capillary-action60_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/capillary-action60_0.jpg","mime":"image\/jpeg","size":1325301,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/capillary-action60_0.jpg?itok=egfik9mx"}}},"media_ids":["428381","428391","428401"],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"141","name":"Chemistry and Chemical Engineering"},{"id":"145","name":"Engineering"},{"id":"146","name":"Life Sciences and Biology"},{"id":"135","name":"Research"},{"id":"150","name":"Physics and Physical Sciences"}],"keywords":[{"id":"2781","name":"Andrei Fedorov"},{"id":"136721","name":"capillary action"},{"id":"3356","name":"hydrogel"},{"id":"7343","name":"lab-on-a-chip"},{"id":"12427","name":"microfluidics"},{"id":"1492","name":"Polymer"}],"core_research_areas":[{"id":"39441","name":"Bioengineering and Bioscience"},{"id":"39471","name":"Materials"},{"id":"39491","name":"Renewable Bioproducts"}],"news_room_topics":[{"id":"71881","name":"Science and Technology"}],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EJohn Toon\u003C\/p\u003E\u003Cp\u003EResearch News\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003E(404) 894-6986\u003C\/p\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}},"428191":{"#nid":"428191","#data":{"type":"news","title":"Ultra-thin Hollow Nanocages Could Reduce Platinum Use in Fuel Cell Electrodes","body":[{"value":"\u003Cp\u003EA new fabrication technique that produces platinum hollow nanocages with ultra-thin walls could dramatically reduce the amount of the costly metal needed to provide catalytic activity in such applications as fuel cells.\u003C\/p\u003E\u003Cp\u003EThe technique uses a solution-based method for producing atomic-scale layers of platinum to create hollow, porous structures that can generate catalytic activity both inside and outside the nanocages. The layers are grown on palladium nanocrystal templates, and then the palladium is etched away to leave behind nanocages approximately 20 nanometers in diameter, with between three and six atom-thin layers of platinum.\u003C\/p\u003E\u003Cp\u003EUse of these nanocage structures in fuel cell electrodes could increase the utilization efficiency of the platinum by a factor of as much as seven, potentially changing the economic viability of the fuel cells.\u003C\/p\u003E\u003Cp\u003E\u201cWe can get the catalytic activity we need by using only a small fraction of the platinum that had been required before,\u201d said Younan Xia, a professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. Xia also holds joint faculty appointments in the School of Chemistry and Biochemistry and the School of Chemical and Biomolecular Engineering at Georgia Tech. \u201cWe have made hollow nanocages of platinum with walls as thin as a few atomic layers because we don\u2019t want to waste any material in the bulk that does not contribute to the catalytic activity.\u201d\u003C\/p\u003E\u003Cp\u003EThe research \u2013 which also involved researchers at the University of Wisconsin-Madison, Oak Ridge National Laboratory, Arizona State University and Xiamen University in China \u2013 was reported in the July 24 issue of the journal \u003Cem\u003EScience\u003C\/em\u003E.\u003C\/p\u003E\u003Cp\u003EPlatinum is in high demand as a catalyst for a wide range of industrial and consumer applications. The high cost of platinum needed for the catalysts deposited on electrodes has limited the ability to use low-temperature fuel cells in automobiles and home applications.\u003C\/p\u003E\u003Cp\u003EIn catalytic applications, only the surface layers of platinum contribute to the chemical reaction, leading researchers to develop new structures designed to maximize the amount of platinum exposed to reactants. The hollowing out process reduces the amount of the precious metal not contributing to the reaction, and allows the use of larger nanocrystals that are less susceptible to sintering, an aggregation phenomenon which reduces catalyst surface area.\u003C\/p\u003E\u003Cp\u003E\u201cWe can control the process so well that we have layer-by-layer deposition, creating one layer, two layers or three layers of platinum,\u201d said Xia, who is also a Georgia Research Alliance eminent scholar. \u201cWe can also control the arrangement of atoms on the surface so their catalytic activity can be engineered to fit different types of reactions.\u201d\u003C\/p\u003E\u003Cp\u003EHollow platinum structures have been made before, but not with walls this thin, he added.\u003C\/p\u003E\u003Cp\u003EEarlier work produced shells with wall thicknesses of approximately five nanometers. The new process can produce shell walls less than one nanometer thick. With both the inner layer and outer layer of the porous nanocages contributing to the catalytic activity, the new structures can use up to two-thirds of the platinum atoms in an ultra-thin three-layer shell. Some palladium remains mixed with the platinum in the structures.\u003C\/p\u003E\u003Cp\u003E\u201cThis approach creates the highest possible surface area from a given amount of platinum,\u201d said Xia.\u003C\/p\u003E\u003Cp\u003EThe nanocages can be made in either cubic or octahedral shapes, depending on the palladium nanocrystals used as templates. The shape controls the surface structure, thus engineering the catalytic activity.\u003C\/p\u003E\u003Cp\u003EThe goal of this research was to reduce the cost of the cathodes in fuel cells designed to power automobiles and homes. The fuel cell\u2019s oxygen-reduction reaction takes place at the cathode, and that requires a substantial amount of platinum. By reducing the amount of platinum by up to a factor of seven, the hollow shells could make automotive and home fuel cells more economically feasible.\u003C\/p\u003E\u003Cp\u003EThe researchers measured the durability of the platinum nanocages for oxygen-reduction reaction, and found the catalytic activity dropped by a little more than one-third after 10,000 operating cycles. Earlier efforts to maximize surface area relied on making very small platinum nanoparticles just two or three nanometers in diameter. Particles of that size tended to clump together in a process known as sintering, reducing the surface area.\u003C\/p\u003E\u003Cp\u003E\u201cBy using hollow structures, we can use much larger particle sizes \u2013 about 20 nanometers \u2013 and we really don\u2019t lose any surface area because we can use both the inside and outside of the structure, and the shells are only a few atomic layers thick,\u201d Xia added. \u201cWe expect the durability of these larger particles to be much better.\u201d\u003C\/p\u003E\u003Cp\u003EOther applications, such as catalytic converters in automobiles, also use substantial amounts of platinum. The new hollow shells are unlikely to be used in automobile catalytic converters because they operate at a temperature beyond what the structures can tolerate. However, the platinum nanocages could find use in other industrial processes such as hydrogenation.\u003C\/p\u003E\u003Cp\u003EContributing to the experimental work done at Georgia Tech, researchers at Arizona State University and Oak Ridge National Laboratory used their specialized microscopy facilities to map the nanocage structures. Researchers at the University of Wisconsin-Madison modeled the system to help understand etching of palladium from the core while preserving the platinum shell.\u003C\/p\u003E\u003Cp\u003EResearchers have explored alternatives to platinum, but none of the alternatives so far has provided the equivalent amount of catalytic activity in such a small mass, Xia noted.\u003C\/p\u003E\u003Cp\u003E\u201cIf you took all of the platinum that we have available today and made a cube, it would only be seven meters on each side,\u201d he added. \u201cThat\u2019s all the platinum we have now, so we need to find the most efficient way to use it.\u201d\u003C\/p\u003E\u003Cp\u003EOther authors in the paper include Professor Manos Mavrikakis and researchers Luke Roling and Jeffrey Herron from the University of Wisconsin-Madison, Miaofang Chi from Oak Ridge National Laboratory, Professor Jingyue Liu from Arizona State University, Professor Zhaoxiong Xie from Xiamen University, and Lei Zhang, Xue Wang, Sang-Il Choi, Madeleine Vara and Jinho Park, from Georgia Tech.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ECITATION\u003C\/strong\u003E: Lei Zhang, et al., \u201cPlatinum-based nanocages with subnanometer-thick walls and well-defined, controllable facets,\u201d (Science, 2015).\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EResearch News\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EGeorgia Institute of Technology\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003E177 North Avenue\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EAtlanta, Georgia 30332-0181 USA\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EMedia Relations\u003C\/strong\u003E: John Toon (\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E) (404-894-6986)\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EA new fabrication technique that produces platinum hollow nanocages with ultra-thin walls could dramatically reduce the amount of the costly metal needed to provide catalytic activity in such applications as fuel cells.\u0026nbsp;\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"A new fabrication technique could reduce the amount of platinum needed for fuel cell electrodes."}],"uid":"27303","created_gmt":"2015-07-23 16:33:24","changed_gmt":"2016-10-08 03:19:15","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2015-07-23T00:00:00-04:00","iso_date":"2015-07-23T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"428131":{"id":"428131","type":"image","title":"Platinum hollow nanocages","body":null,"created":"1449254342","gmt_created":"2015-12-04 18:39:02","changed":"1475895167","gmt_changed":"2016-10-08 02:52:47","alt":"Platinum hollow nanocages","file":{"fid":"202807","name":"platinum-nanocages.jpg","image_path":"\/sites\/default\/files\/images\/platinum-nanocages_1.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/platinum-nanocages_1.jpg","mime":"image\/jpeg","size":830396,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/platinum-nanocages_1.jpg?itok=GGVeANTv"}},"428161":{"id":"428161","type":"image","title":"Platinum hollow nanocages2","body":null,"created":"1449254342","gmt_created":"2015-12-04 18:39:02","changed":"1475895167","gmt_changed":"2016-10-08 02:52:47","alt":"Platinum hollow nanocages2","file":{"fid":"202809","name":"platinum-nanocages2.jpg","image_path":"\/sites\/default\/files\/images\/platinum-nanocages2_1.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/platinum-nanocages2_1.jpg","mime":"image\/jpeg","size":1153737,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/platinum-nanocages2_1.jpg?itok=eUA99BU6"}},"428171":{"id":"428171","type":"image","title":"Platinum hollow nanocages3","body":null,"created":"1449254342","gmt_created":"2015-12-04 18:39:02","changed":"1475895167","gmt_changed":"2016-10-08 02:52:47","alt":"Platinum hollow nanocages3","file":{"fid":"202810","name":"platinum_nanocages1.jpg","image_path":"\/sites\/default\/files\/images\/platinum_nanocages1_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/platinum_nanocages1_0.jpg","mime":"image\/jpeg","size":1091708,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/platinum_nanocages1_0.jpg?itok=5mRc0z_d"}},"428181":{"id":"428181","type":"image","title":"Platinum hollow nanocages4","body":null,"created":"1449254342","gmt_created":"2015-12-04 18:39:02","changed":"1475895167","gmt_changed":"2016-10-08 02:52:47","alt":"Platinum hollow nanocages4","file":{"fid":"202811","name":"platinum-nanocages3.jpg","image_path":"\/sites\/default\/files\/images\/platinum-nanocages3_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/platinum-nanocages3_0.jpg","mime":"image\/jpeg","size":875879,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/platinum-nanocages3_0.jpg?itok=dVlNqWf8"}}},"media_ids":["428131","428161","428171","428181"],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"145","name":"Engineering"},{"id":"149","name":"Nanotechnology and Nanoscience"},{"id":"135","name":"Research"}],"keywords":[{"id":"2506","name":"catalyst"},{"id":"2044","name":"Fuel Cell"},{"id":"136641","name":"nanocage"},{"id":"107","name":"Nanotechnology"},{"id":"7531","name":"platinum"},{"id":"24841","name":"Younan Xia"}],"core_research_areas":[{"id":"39531","name":"Energy and Sustainable Infrastructure"},{"id":"39471","name":"Materials"}],"news_room_topics":[{"id":"71881","name":"Science and Technology"}],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EJohn Toon\u003C\/p\u003E\u003Cp\u003EResearch News\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003E(404) 894-6986\u003C\/p\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}