Restructuring In Core-Shell Particles

A study that examined the structural and chemical changes taking place in bimetallic nanoparticles under different reaction conditions has set the stage for designing and fine-tuning "smart" nanoparticle catalysts on the basis of their composition (Science, DOI: 10.1126/science.1164170). Gabor A. Somorjai and Miquel Salmeron of the University of California, Berkeley, and Lawrence Berkeley National Laboratory and colleagues studied so-called core-shell nanoparticles in which a spherical core composed of one element is surrounded by a thin shell of another. Using ambient pressure X-ray photoelectron spectroscopy, the researchers compared the chemical behavior of Rh-Pd and Pd-Pt nanoparticles during reactions involving NO, O₂, CO, and H₂. They found that the Rh-Pd nanoparticles undergo striking reversible rearrangements, with palladium migrating into the shell and rhodium migrating into the core. The Pd-Pt nanoparticles didn't exhibit this behavior under the same reaction conditions.