Somorjai and Salmeron have for many years been collaborating on the development of instrumentation and techniques that enable them to do catalysis studies under realistic conditions. They now have at their disposal unique high-pressure scanning tunneling microscopes (STM) and an ambient pressure x-ray photoelectron spectroscopy (AP-XPS) beamline operating at the Berkeley Lab's Advanced Light Source, a premier source of synchrotron radiation for scientific research.
"With these two resources, we can image the atomic structure and identify the chemical state of catalyst atoms and adsorbed reactant molecules under industrial-type pressures and temperatures," Salmeron says.
STM images revealed the formation of nanoclusters on the platinum crystal surfaces, and the AP-XPS spectra revealed a change in carbon monoxide electron binding energies. A subsequent collaboration with Lin-Wang Wang, a theorist in Berkeley Lab's Computational Sciences Division, explained the change in structure as the result of the relaxation of the strong repulsion between carbon monoxide molecules that arises from their very high density on the surface when in equilibrium with elevated pressures of the gas.
"In the future, the use of these stable platinum nanoclusters as fuel cell catalysts may help to boost performance and reduce costs," Somorjai says.
The next step for Somorjai and Salmeron and their research team will be to determine whether other adsorbed reactants, such as oxygen or hydrogen, also result in the creation of nanoclusters in platinum. They also want to know if nanoclusters can be induced in other metal catalysts as well, such as palladium, silver, copper, rhodium, iron and cobalt.
"If this nanoclustering is a general phe
|Contact: Lynn Yarris|
DOE/Lawrence Berkeley National Laboratory