NEWS OF THE WEEK
MAKING HYDROGEN MATERIALS: Core-shell nanowires aid
quest to produce renewable fuel
power of the sun to convert cheap, abundant resources to valuable fuels such as hydrogen, and do so in an inexpensive and sustainable way, they will have taken a big step toward solving the world’s energy problems. The potential payoff is driving a worldwide effort to find a practical light-driven way to split water and extract hydrogen, an environmentally friendly fuel. The problem has not yet been solved. But the development by researchers at Duke University of a low-cost, transparent water-splitting catalyst now moves the field closer to its goal. Hydrogen can be liberated from water by several means. Some processes are energy demanding, such as electrolysis. And some require platinum and other costly materials. In one potentially low-cost method, sunlight enters a specially designed cell and triggers a multistep electrochemical process that begins with waANGEW. CHEM. INT. ED.
A mesh of copper nanowires coated with nickel (seen in micrograph) or cobalt forms a catalytically active transparent electrode for splitting water in electrochemical cells (photo).
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F SCIENTISTS CAN FIGURE OUT how to tap the
MORE HELIUM ON THE WAY BY 2015 INDUSTRIAL GAS: New Air Products facility will help bolster slowing U.S. production
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instrument operators, and other helium users will face at least another year of high prices and low supplies of the gas. After that, things should start looking up, thanks in part to a new Air Products & Chemicals project in Doe Canyon, Colo. The industrial gases firm will separate helium from naturally occurring underground carbon dioxide that is extracted by Kinder Morgan CO2 and piped to Texas for use in enhanced oil recovery. The project is the first new source of helium to be announced in three years, according to John Campbell of the gases consulting firm J.R. Campbell & Associates. The announcement is timely; supplies U.S. NAV Y
Weather balloons require helium to get aloft.
ALLOON LOVERS, nuclear magnetic resonance
CEN.ACS.ORG
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ter oxidation on a catalyst surface. That reaction produces O2 and frees electrons and protons, which can be combined to yield H2. These photoelectrochemical cells often depend on indium tin oxide (ITO), a transparent, electrically conductive material, coated with a catalytic metal oxide. Because of its ability to serve as a transparent electrode, ITO is the go-to material for various photoelectrochemical processes—not just making H2—and other applications. But indium and ITO are expensive. In addition, the catalytic oxide layer reduces ITO’s light transmission and thus cell efficiency, and its conductivity falls with extended use. To sidestep these limitations, Duke chemists Zuofeng Chen, Benjamin J. Wiley, and coworkers have developed an ITO replacement—copper nanowires coated with a shell of nickel or cobalt (Angew. Chem. Int. Ed. 2013, DOI: 10.1002/anie.201306585). Initial tests show that a mesh of this inexpensive, transparent, conductive material exhibits sustained water oxidation activity comparable to that of metal oxide films, but transmits nearly seven times more light. In addition, the material can be deposited on glass or plastic substrates via simple liquid-phase methods, which may lead to new types of robust, flexible photoelectrochemical cells and other devices. Brown University catalysis specialist Andrew A. Peterson notes that keeping the copper core in its reduced metallic form under oxidizing conditions will be challenging. “Nonetheless, this is an interesting direction,” he says.—MITCH JACOBY
of helium from the Federal Helium Reserve in Amarillo, Texas, are declining at an accelerating rate. The facility, responsible for about 30% of global helium supply, came close to shutting down entirely this year before Congress reauthorized the sale of helium in October. Falling helium recovery from natural gas reserves, along with production glitches and plant shutdowns, has added to the supply crunch. The Doe Canyon plant is expected to produce up to 230 million cu ft per year, equivalent to more than 15% of the Federal Helium Reserve’s annual distribution. Air Products also has a joint venture with Matheson Tri-Gas to process helium in Wyoming, but it hasn’t stated when production will start. Meanwhile, Air Liquide built a large plant in Qatar that has begun purifying helium from natural gas. It will eventually have an capacity of 2.1 billion cu ft. Still, global supply shortages are expected to continue through 2014. Global demand for helium is rising, particularly in Asia for use in electronics production and magnetic resonance imaging equipment, while supply is not, Campbell points out. “The Air Products project won’t solve the shortage on its own but will reinforce Air Products’ premier position as a supplier with reliable production. It’s also a significant new investment at a time when price is going up due to scarcity.”—MELODY BOMGARDNER
NOVEMBER 4, 2013
