Travelling atoms discard electrons that prove vital to bonding oxygen on catalyst, cleanup

June 15, 2010
To settle down on the surface of titanium dioxide, oxygen atoms need a few electrons.

( -- To settle down on the surface of titanium dioxide, oxygen atoms need a few electrons. The source of these electrons has been under debate: do the electrons come from the surface or from deep down within? Now, scientists from Pacific Northwest National Laboratory have proven that the electrons come from the surface of the titanium dioxide. The needed electrons are left by oxygen atoms that pack up and move to other locations.

This research was featured on the inside cover of the themed issue on characterizing absorbed species in Physical Chemistry Chemical Physics.

It is often said that understanding is the first step in controlling. This advice applies to habits you want to change and you want to control. So, to control a reaction that converts plant matter into fuels, researchers must first understand it. That's what this study does. It provides understanding.

The factors that determine whether or not oxygen will bond with a surface is vital to controlling reactions for converting to fuels, treating waste, and purifying water, among other reactions. This research shows the vital role oxygen vacancies play in supplying to form bonds between a metal atom from the catalyst substrate and introduced oxygen.

To determine the source of the electrons needed to bond oxygen to the surface of , the research team drew together experts in experimentation and theory.

The researchers began with titanium dioxide because, in addition to being a common , is a model metal oxide, typically used in these studies. To see the surface of titanium dioxide, imagine rows of neatly ordered pool balls. These are the titanium atoms. Now, arrange another row on top. The spheres rest between the others. This new row is the .

Using scanning tunneling microscopy, the team followed the behavior of oxygen atoms at specific locations on the titanium dioxide's surface. "Being able to watch the same location over time was key," said Dr. Igor Lyubinetsky, a chemist at Pacific Northwest National Laboratory who led the study.

With the data from the microscope and other resources, the team did detailed density functional theory calculations. They determined that when molecular oxygen or O2 reacts with titanium dioxide's surface, the oxygen dissociates into two adatoms, or charged oxygen atoms. These atoms use the electrons from the vacancies to bond on top of titanium atoms on the surface. Then, repulsive Coulombic forces cause the bonded oxygen adatoms to move apart quickly.

Next, the researchers are investigating how oxygen physisorbs or weakly interacts with the titanium dioxide at low temperatures. "This is another big mystery out there," said Dr. Zdenek Dohnálek, a key scientist on this research. "And, it is another place where STM [scanning electron microscopy] could have the answers. "

Explore further: Scientists see carbon chains preferred locales on popular catalyst

More information: Du Y, NA Deskins, Z Zhang, Z Dohnálek, M Dupuis, and I Lyubinetsky. 2010. "Formation of O Adatom Pairs and Charge Transfer upon O2 Dissociation on Reduced TiO2(110)." Physical Chemistry Chemical Physics 12, 6337-6344. DOI:10.1039/c000250j

Related Stories

Graphene-Based Nanomat Could Lead to Next-Generation Catalysts

January 19, 2010

( -- Researchers have found a new use for graphene, the single-atom-thick sheet of carbon atoms that resembles chicken wire. Ever since graphene was first observed in 2004, its large surface area, excellent mechanical ...

Uniform tungsten trimers stand and deliver

September 18, 2006

Like tiny nano-soldiers on parade, the cyclic tungsten trioxide clusters line up molecule-by-molecule on the titanium dioxide platform. One tungsten atom from each cluster is raised slightly, holding forth the potential to ...

Recommended for you

New X-ray spectroscopy explores hydrogen-generating catalyst

November 22, 2017

Using a newly developed technique, researchers from Japan, Germany and the U.S. have identified a key step in production of hydrogen gas by a bacterial enzyme. Understanding these reactions could be important in developing ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.