RICHLAND, Wash. -- Single oxygen atoms dancing on a metal oxide slab, glowing brighter here and dimmer there, have helped chemists better understand how water splits into oxygen and hydrogen. In the process, the scientists have visualized a chemical reaction that had previously only been talked about. The new work improves our understanding of the chemistry needed to generate hydrogen fuel from water or to clean contaminated water.
The scientists 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 at the Department of Energy's Pacific Northwest National Laboratory, who reported the team's results in March 6 issue of the Physical Review Letters. "This mobility might interfere with some reactions and help others."
Bustling Bright Spots
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". Chemists can only see water molecules if they drop the temperature dramatically -- at ambient temperature, water moves too fast for the method to pick them up.
In this work, PNNL scientists studied water's reactions with titanium dioxide at ambient temperature
|Contact: Mary Beckman|
DOE/Pacific Northwest National Laboratory