{"id":10215,"date":"2016-10-05T08:00:56","date_gmt":"2016-10-05T08:00:56","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=10215"},"modified":"2016-10-05T08:00:56","modified_gmt":"2016-10-05T08:00:56","slug":"water-vapor-sets-some-oxides-aflutter","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/water-vapor-sets-some-oxides-aflutter\/","title":{"rendered":"Water vapor sets some oxides aflutter"},"content":{"rendered":"

Newly discovered phenomenon could affect materials in batteries and water-splitting devices.<\/strong><\/em><\/span><\/p>\n

\"These<\/a>
These images, taken from a transmission electron microscope, show a perovskite material oscillating as it is exposed to water vapor and a beam of electrons.
Courtesy of the researchers<\/figcaption><\/figure>\n

CAMBRIDGE, Mass<\/strong>. — When one type of an oxide structure called perovskite is exposed to both water vapor and streams of electrons, it exhibits behavior that researchers had never anticipated: The material gives off oxygen and begins oscillating, almost resembling a living, breathing organism.<\/span><\/p>\n

The phenomenon was \u201ctotally unexpected\u201d and may turn out to have some practical applications, says Yang Shao-Horn, the W.M. Keck Professor of Energy at MIT. She is the senior author of a paper describing the research that is being published in the journal\u00a0Nature Materials<\/em>. The paper\u2019s lead author is Binghong Han PhD \u201916, now a postdoc at Argonne National Laboratory.<\/span><\/p>\n

Perovskite oxides are promising candidates for a variety of applications, including solar cells, electrodes in rechargeable batteries, water-splitting devices to generate hydrogen and oxygen, fuel cells, and sensors. In many of these uses, the materials would be exposed to water vapor, so a better understanding of their behavior in such an environment is considered important for facilitating the development of many of their potential applications.<\/span><\/p>\n

Like cooking polenta<\/strong><\/span><\/p>\n

When a particular kind of perovskite known as BSCF \u2014 after the chemical symbols for its constituents barium, strontium, cobalt, and iron \u2014 is placed in a vacuum in a transmission electron microscope (TEM) to observe its behavior, Shao-Horn says, \u201cnothing happens, it\u2019s very stable.\u201d But then, \u201cwhen you pump in low pressure water vapor, you begin to see the oxide oscillate.\u201d The cause of that oscillation, clearly visible in the TEM images, is that \u201cbubbles form and shrink in the oxide. It\u2019s like cooking a polenta, where bubbles form and then shrink.\u201d<\/span><\/p>\n

[pullquote]Despite all the pulsating motion and the penetration of ions in and out of the solid crystalline material, when the reaction stops, the material \u201cstill has its original perovskite structure,\u201d Han says.[\/pullquote]<\/p>\n

The behavior was so unexpected in part because the oxide is solid and was not expected to have the flexibility to form growing and shrinking bubbles. \u201cThis is incredible,\u201d Shao-Horn says. \u201cWe think of oxides as brittle,\u201d but in this case the bubbles expand and contract without any fracturing of the material. And in the process of bubble formation, \u201cwe are actually generating oxygen gas,\u201d she says.<\/span><\/p>\n

What\u2019s more, the exact frequency of the oscillations that are generated by the forming and bursting bubbles can be precisely tuned, which could be a useful feature for some potential applications. \u201cThe magnitude and frequency of the oscillations depend on the pressure\u201d of the vapor in the system, Shao-Horn says. And since the phenomenon also depends on the presence of electron beams, the reaction can be switched on and off at will by controlling those beams.<\/span><\/p>\n

The effect is not just a surface reaction, she says. The water molecules, which become ionized (electrically charged) by the electron beam, actually penetrate deep into the perovskite. \u201cThese ions go inside the bulk material, so we see oscillations coming from very deep,\u201d she says.<\/span><\/p>\n

This experiment used the unique capabilities of an \u201cenvironmental\u201d transmission electron microscope at Brookhaven National Laboratory, part of a U.S. Department of Energy-supported facility there. With this instrument, the researchers directly observed the interaction between the perovskite material, water vapor, and streams of electrons, all at the atomic scale.<\/span><\/p>\n

Keeping its shape<\/strong><\/span><\/p>\n

Despite all the pulsating motion and the penetration of ions in and out of the solid crystalline material, when the reaction stops, the material \u201cstill has its original perovskite structure,\u201d Han says.<\/span><\/p>\n

Because this is such a new and intriguing finding, Shao-Horn says, \u201cwe still don\u2019t understand in full detail\u201d exactly how the reactions take place, so the research is continuing in order to clarify the mechanisms. \u201cIt\u2019s an unexpected result that opens a lot of questions to address scientifically.\u201d<\/span><\/p>\n

While the initial experiments used electron beams, Shao-Horn questions if such behavior could also be induced by shining a bright light, which could be a useful approach for water splitting and purification \u2014 for example, using sunlight to generate hydrogen fuel from water or remove toxins from water.<\/span><\/p>\n

While most catalysts promote reactions only at their surfaces, the fact that this reaction penetrates into the bulk of the material suggests that it could offer a new mechanism for catalyst designs, she says.<\/span><\/p>\n

In addition to mechanical engineering, Shao-Horn holds joint appointments with the Department of Materials Science and Engineering and the MIT Energy Initiative\u2019s Center for Energy Storage. The research team also included Kelsey Stoerzinger PhD \u201916; Vasili Tileli of the Ecole Polytechnique Federale de Lausanne, in Switzerland; and Andrew Gamalski and Eric Stach of Brookhaven National Laboratory, in Upton, New York. The work was supported by the National Science Foundation, the Skoltech-MIT Center for Electrochemical Energy Storage, and the U.S. Department of Energy Office of Science.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

When one type of an oxide structure called perovskite is exposed to both water vapor and streams of electrons, it exhibits behavior that researchers had never anticipated: The material gives off oxygen and begins oscillating, almost resembling a living, breathing organism.<\/p>\n","protected":false},"author":6,"featured_media":10216,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-10215","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/MIT-Water-Oxide_0-1.jpg",639,426,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/MIT-Water-Oxide_0-1-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/MIT-Water-Oxide_0-1-300x200.jpg",300,200,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/MIT-Water-Oxide_0-1.jpg",639,426,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/MIT-Water-Oxide_0-1.jpg",639,426,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/MIT-Water-Oxide_0-1.jpg",639,426,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/MIT-Water-Oxide_0-1.jpg",639,426,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/MIT-Water-Oxide_0-1.jpg",639,426,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/MIT-Water-Oxide_0-1.jpg",639,426,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/MIT-Water-Oxide_0-1.jpg",600,400,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/MIT-Water-Oxide_0-1.jpg",600,400,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/MIT-Water-Oxide_0-1.jpg",639,426,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/MIT-Water-Oxide_0-1.jpg",540,360,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/MIT-Water-Oxide_0-1.jpg",95,63,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/MIT-Water-Oxide_0-1.jpg",639,426,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/MIT-Water-Oxide_0-1.jpg",96,64,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/MIT-Water-Oxide_0-1.jpg",150,100,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Research<\/a>","tag_info":"Research","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/10215","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=10215"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/10215\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/10216"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=10215"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=10215"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=10215"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}