Dancing atoms help chemists understand how water molecules split

March 17th, 2009 - 4:48 pm ICT by ANI  

Washington, March 17 (ANI): Chemists have used single oxygen atoms dancing on a metal oxide slab, to get a better understanding of how water splits into oxygen and hydrogen, which would improve their understanding of the chemistry needed to generate hydrogen fuel from water or to clean contaminated water.
The scientists, from the Department of Energy’’s Pacific Northwest National Laboratory (PNNL), made the discovery while trying to determine the basics of how titanium dioxide - a compound sometimes found in sunscreen - breaks down water.
The chemical reactions between water and oxygen are central to such varied processes as hydrogen production, breaking down pollutants, and in solar energy.
“Oxygen and water are involved in many, many reactions,” said physicist Igor Lyubinetsky from the Pacific Northwest National Laboratory. “This mobility might interfere with some reactions and help others,” he added.
While exploring titanium dioxide as a way to split water into its hydrogen and oxygen pieces, researchers can use a technique called scanning tunneling microscopy to watch the chemical reaction.
The surface of a slab of titanium dioxide is like a corn field: rows of oxygen atoms rise from a patch of titanium atoms.
The alternating oxygen and titanium rows look like stripes.
Scientists can also see some atoms and molecules that come to rest on the surface as bright spots.
One such visible atom is a single oxygen atom that comes to rest on a titanium atom, called an “adatom”.
In the new research, PNNL scientists studied water’’s reactions with titanium dioxide at ambient temperature.
Starting with a surface plated with a few oxygen adatoms, they added water - and the adatoms started to dance.
“Suddenly, almost every adatom started to move back and forth along the titanium row. From theory and previous work, we expected to see this along the row,” said Lyubinetsky.
Remarkably, the adatoms didn”t just slide up and down the stripes. They also bounced out of them and landed in others, like pogoing dancers in a mosh pit.
“We saw quite unexpected things. We thought it was very strange. We saw adatoms jump over the rows. We just couldn”t explain it,” Lyubinetsky said.
Calculating how much energy it would take for the adatoms to move by themselves, the chemists suspected the adatoms were getting help - most likely from the invisible water molecules.
The chemists determined that water can help the adatom jump a row.
If a water molecule and an adatom are situated on either side of a raised oxygen row, a row oxygen can serve as the middleman, handing over a hydrogen from the water molecule to the adatom. (ANI)

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