Locating Active Catalytic Sites

9 June 2006

Developing and optimizing catalysts is a critical component for the energy, fuels and transportation industries. However, precisely locating a catalyst’s active chemical sites is difficult, even though some methods can provide surface structure maps with atomic resolution.

Chemical Engineering and News reports that a pair of researchers from the University of California, Riverside, have now developed methods that reveal site-specific chemistry on catalyst surfaces.

The technique, which combines titration procedures with surface spectroscopy, identifies the nature of the sites to which specific reagent molecules bond and the selectivity of that process—key steps in understanding reaction mechanisms.

Chemistry professor Francisco Zaera and postdoc Hansheng Guo demonstrated their new method on a nickel crystal that had been treated with various amounts of oxygen. The crystal, which is characterized by fragmented Ni-O rows, serves as a model catalyst for transition-metal-mediated oxidation reactions.

Understanding the nature of the active sites that drive certain chemical transformations is an important but often elusive goal in catalytic studies, says Daniel R. Strongin, a chemistry professor at Temple University, Philadelphia, and a specialist in surface science.

Zaera’s group has developed “an elegant methodology,” Strongin comments, using xenon as a probe to elucidate the chemical nature of the sites that exhibit selective binding toward catalytically relevant molecules. He adds that the methodology is general enough to have the potential to be applicable to many chemically important systems.