To determine how these nanocatalysts work, the research team developed so-called inverse model catalysts. The WGS catalysts usually consist of gold nanoparticles dispersed on a ceria or titania surface a small amount of the expensive metal placed on the inexpensive oxide. But to get a better look at the surface interactions, the researchers placed ceria or titania nanoparticles on a pure gold surface.
For the first time, we established that although pure gold is inert for the WGS reaction, if you put a small amount of ceria or titanium on it, it becomes extremely active, Rodriguez said. So although these inverse catalysts are just models, they have catalytic activity comparable to, and sometimes better than, the real deal.
Using a technique called x-ray photoelectron spectroscopy at Brookhavens National Synchrotron Light Source, as well as scanning tunneling microscopy and calculations, the researchers discovered that the catalysts oxides are the reason for their high activity.
The oxides have unique properties on the nanoscale and are able to break apart water molecules, which is the most difficult part of the WGS reaction, Hrbek said. Added Brookhaven physicist Ping Liu: After you dissociate the water, the reaction continues on to eliminate CO. But if you dont have nanosized oxide particles, none of this will work.
The researchers plan to continue their study of these catalysts at the NSLS and CFN in order to further explore the reaction mechanism and optimize its performance.
|Contact: Karen McNulty Walsh|
DOE/Brookhaven National Laboratory