Subscribe free to our newsletters via your
. 24/7 Space News .




ENERGY TECH
A Better Look at the Chemistry of Interfaces
by Staff Writers
Berkeley CA (SPX) Dec 03, 2014


By utilizing X-ray standing waves to excite photoelectrons, SWAPPS delivers vital information about all the chemical elements at the heterogeneous interfaces found in batteries, fuel cells and other devices.

Researchers working at the Advanced Light Source (ALS) of the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) have combined key features of two highly acclaimed X-ray spectroscopy techniques into a new technique that offers sub-nanometer resolution of every chemical element to be found at heterogeneous interfaces, such as those in batteries and fuel cells.

This new technique is called SWAPPS for Standing Wave Ambient Pressure Photoelectron Spectroscopy, and it combines standing-wave photoelectron spectroscopy (SWPS) with high ambient pressure photoelectron spectroscopy (APPS).

"SWAPPS enables us to study a host of surface chemical processes under realistic pressure conditions and for systems related to energy production, such as electrochemical cells, batteries, fuel cells and photovoltaic cells, as well as in catalysis and environmental science," says Charles Fadley, a physicist who holds joint appointments with Berkeley Lab's Materials Sciences Division and the University of California Davis, where he is a Distinguished Professor of Physics.

"SWAPPS provides all the advantages of the widely used technique of X-ray photoelectron spectroscopy, including element and chemical-state sensitivity, and quantitative analysis of relative concentrations of all species present. However with SWAPPS we don't require the usual ultrahigh vacuum, which means we can measure the interfaces between volatile liquids and solids."

Fadley is one of three corresponding authors of a paper describing SWAPPS in Nature Communications. The paper is titled "Concentration and chemical-state profiles at heterogeneous interfaces with sub-nm accuracy from standing-wave ambient-pressure photoemission."

The other two corresponding authors are Hendrik Bluhm, with Berkeley Lab's Chemical Sciences Division, a pioneer in the development of APPS, and Slavomir Nemsak, now with Germany's Julich Peter Grunberg Institute. (See below for the complete list of authors).

In terms of energies and wavelengths, X-rays serve as excellent probes of chemical processes. In the alphabet soup of X-ray analytical techniques, two in particular stand out for the study of chemistry at the interface where layers of two different materials or phases of matter meet.

The first is SWPS, developed at the ALS by Fadley and his research group, which made it possible for the first time to selectively study buried interfaces in a sample with either soft or hard X-rays. The second is APPS, also developed at the ALS by a team that included Bluhm, which made it possible for the first time to use X-ray photoelectron spectroscopy under pressures and humidities similar to those encountered in natural or practical environments.

"Heterogeneous processes at solid/gas, liquid/gas and solid/liquid interfaces are ubiquitous in modern devices and technologies but often difficult to study quantitatively," Bluhm says.

"Full characterization requires measuring the depth profiles of chemical composition and state with enhanced sensitivity in narrow interfacial regions at the nanometer scale. By combining features of SWPS and APPS techniques, we can use SWAPPS to measure the elemental and chemical composition of heterogeneous interfaces with sub-nanometer resolution in the direction perpendicular to the interface."

Says Fadley, "We believe SWAPPS will deliver vital information about the structure and chemistry of liquid/vapor and liquid/solid interfaces, in particular the electrical double layer whose structure is critical to the operation of batteries, fuel cells and all of electrochemistry, but which is still not understood at a microscopic level."

Fadley, Bluhm, Nemsak and their collaborators used their SWAPPS technique to study a model system in which a nanometer layer of an aqueous electrolyte of sodium hydroxide and cesium hydroxide was grown on an iron oxide (hematite) solid.

The spatial distributions of the electrolyte ions and the carbon contaminants across the solid/liquid and liquid/gas interfaces were directly probed and absolute concentrations of the chemical species were determined. The observation of binding-energy shifts with depth provided additional information on the bonding and/or depth-dependent potentials in the system.

"We determined that the sodium ions are located close to the iron oxide/solution interface, while cesium ions are on average not in direct contact with the solid/liquid interface," Bluhm says.

"We also discovered that there are two different kinds of carbon species, one hydrophobic, which is located exclusively in a thin film at the liquid/vapor interface, and a hydrophilic carbonate or carboxyl that is evenly distributed throughout the liquid film."

A key to the success of this study was the use of X-ray standing waves to excite the photoelectrons. A standing wave is a vibrational pattern created when two waves of identical wavelength interfere with one another: one is the incident X-ray and the other is the X-ray reflected by a mirror. Interactions between standing waves and core-level electrons reveal much about the depth distributions of each chemical species in a sample.

"Tailoring the X-ray wave field into a standing wave can be used to achieve greater depth sensitivity in photoelectron spectroscopy," Fadley says. "Our combination of an oscillatory standing-wave field and the exponential decay of the photoelectron signal at each interface gives us unprecedented depth resolution."

In their Nature Communications paper, the authors say that future time-resolved SWAPPS studies using free-electron laser or high-harmonic generation light sources would also permit, via pump-probe methods, looking at the timescales of processes at interfaces on the femtosecond time scale.

"The range of future applications and measurement scenarios for SWAPPS is enormous," Fadley says.

This work was carried out at ALS Beamline 11.0.2, which is operated by Berkeley Lab's Chemical Sciences Division and hosts two ambient-pressure photoemission spectroscopy endstations.

In addition to Fadley, Bluhm and Nemsak, other authors of the Nature Communications paper describing SWAPPS were Andrey Shavorskiy, Osman Karslioglu, Ioannis Zegkinoglou, Peter Greene, Edward Burks, Arunothai Rattanachata, Catherine Conlon, Armela Keqi, Farhad Salmassi, Eric Gullikson, See-Hun Yang and Kai Liu.

This research was primarily funded by the DOE Office of Science. The Advanced Light Source is a DOE Office of Science User Facility.


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only

.


Related Links
Lawrence Berkeley National Laboratory (Berkeley Lab)
Powering The World in the 21st Century at Energy-Daily.com






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





ENERGY TECH
Corvus Energy Team Powers New Hybrid Research Vessel
Richmond BC (SPX) Dec 03, 2014
Corvus Energy, Northern Lights and BAE systems now power Spirit of the Sound, a floating marine education classroom and research vessel. The vessel, a 65 - foot catamaran, will operate in Long Island Sound for The Norwalk Aquarium in Connecticut. The Corvus Energy lithium battery will provide the high - density energy storage for propulsion and house loads. Two 100kw diesel Lugger L1064A g ... read more


ENERGY TECH
Carnegie Mellon Unveils Lunar Rover "Andy"

Why we should mine the moon

Young Volcanoes on the Moon

Russia Preparing Joint Moon Exploration Agreement With EU

ENERGY TECH
Red Planet's Mystery

Meteorite From Mars Contains Alien Biomass

Traces of possible Martian biological activity inside a meteorite

Meteorite stirs life-on-Mars debate

ENERGY TECH
Lockheed Martin-built Orion takes first steps on deep space journey

UTC Aerospace Systems provides critical control systems for Orion

Orion Flight 'Milestone' in Obama's Space Policy: White House

Orion test sets stage for ESA service module

ENERGY TECH
Service module of China's returned lunar orbiter reaches L2 point

China Launches Second Disaster Relief Satellite

China expects to introduce space law around 2020

China launches new remote sensing satellite

ENERGY TECH
ISS Enables Interplanetary Space Exploration

NASA's CATS Eyes Clouds, Smoke and Dust from the Space Station

3-D Printer Creates First Object in Space on ISS

Soyuz docks at Space Station; Expedition 42 joins crew

ENERGY TECH
Ariane 5 delivers DIRECTV-14 and GSAT-16 to orbit

Launch of European Ariane-5 Space Rocket From Kourou Postponed

Europe to build new-generation Ariane 6 rocket

Soyuz Installed at Baikonur, Expected to Launch Wednesday

ENERGY TECH
'Mirage Earth' exoplanets may have burned away chances for life

Stardust Not Likely to Block Planet Portraits

Finding infant earths and potential life just got easier

Ground-based detection of exoplanets

ENERGY TECH
Researchers develop building material that cools by reflecting heat into space

See it, touch it, feel it

Chemists fabricate novel rewritable paper

Space travel is a bit safer than expected




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.