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Oxygen Has the "Hotties" for TitaniumOxygen atoms behave differently while interacting with titanium crystals |
By Gabriel Gache, Science News Editor
14th of February 2008, 13:50 GMT
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Usually, when a metal catalyst reacts with an oxygen molecule, the individual split oxygen atoms behave in identical ways. It seems that this is not the case when oxygen molecule interacts with titanium metal. When the two oxygen atoms get split up, one remains embedded into the titanium crystalline structure, while the other is free to move a few positions over to another location, after which it is also captured and planted into the titanium metal.
Although titanium is not exceptional as a metal catalyst,
the new findings may lead to the creation of better catalysts for the future fuel cell devices and solar fuel cell, which are thought to power the next generation of vehicles. The study was conducted at the Department of Energy's Pacific Northwest National Laboratory and led by scientist Igor Lyubinetsky.
Oxygen has great affinity towards most of the substances in the periodic table of elements, thus towards metals in general. However, while interacting with titanium, oxygen seems to experience preferential behavior; one of the oxygen atoms extracts energy from the second in order to travel more across the surface, while the other remains embedded in the location where the oxygen molecule was split up. Generally, when such reactions take place, each of the two atoms should get an equal amount of energy.
For example, the oxygen reaction with platinum separates the two oxygen atoms and propels them towards opposite directions, and after traveling a fair distance across the surface of the metal they will eventually stop to form bonds with it. In Chemistry terminology, the atom that receives extra level of energy is called, a 'hot' atom.
While experimenting with a titanium oxide crystal, with titanium and oxygen atoms lined up so that they would form alternating strips on the surface, the researchers successfully created imperfections in the surface of the crystal, by heating it up so that part of the oxygen strips would become vacant. However, while probing the material with a scanning tunneling microscope, the team realized that oxygen molecules only reacted partially with the crystal to fill the vacant positions, meaning soon after the oxygen molecule got split instead of bonding into consecutive vacant positions, one atom would receive more energy and embed itself some positions away from the first one.
Out of a sample of 110 molecules, more than three quarters of the atoms would have jumped one or more positions away from the location of the first. In normal temperature and pressure conditions, the oxygen atoms in the crystal lattice are immobile. But, the team argues that the extra energy received by the 'hot' atom could be received during the bonding process of the first one, and equivalent to about three times more than the energy required to extract an oxygen atom from the crystal, which is spent on moving across the surface.
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