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Revealing the Atomic Restructuring of Pt-Co Nanoparticles

Revealing-the-atomic-restructuring-of-Pt-Co-nanoparticles
Top: Sequential atomic displacement maps of the particle during oxidation. Bottom left: the {111} surface of the Pt-Co nanoparticles after subsequent reduction. Bottom right: cobalt L-edge EELS line profile across the particle overlaid with the line profile across a theoretically modeled particle.

Scientific Achievement
Imaging and spectroscopy of Pt-Co bimetallic nanoparticles during oxidation/reduction gases using an aberration corrected environmental transmission electron microscope (TEM) reveal the atomic restructuring dynamics.

Significance and Impact
The ability to observe atomic scale details of the structural evolution of nanoparticles in their reactive environments opens the way to a deeper understanding of the heterogeneous catalysis. It also allows for the study of a wider variety of nanoparticle systems where reaction pathways remain elusive.

Summary
Haimei Zheng’s team at Berkeley Lab achieved atomic-level in-situ observation of PtCo nanoparticles during oxidation in O2 and reduction in H2 atmospheres using environmental transmission electron microscope (ETEM). We experimentally prove Co migration and strained epitaxial CoO film formation in oxidation, showing that Co reshuffles back to the host particle while leaving a monolayer of platinum on the surface during reduction. This study provides an important reference point for catalytic materials engineering and new catalyst design; furthermore, it makes it possible to design new nanoparticle catalysts with higher catalytic performance.

The ability to observe atomic scale details of nanoparticle structures’ evolution in their reactive environments opens the door to a deeper understanding of the heterogeneous catalysis. It also allows for the study of a wider variety of nanoparticle systems in which reaction pathways remain elusive.

This work is in collaboration with Miquel Salmeron and Gabor Somorjai also of MSD. The study also used BNL and PNNL TEM user facilities – Eric Stach (BNL) and Chongmin Wang (PNNL) are co-authors on the paper. This work is in press in Nano Letters. Collaborators from BNL & PNNL asked for the news release. Lynn Yarris from LBL News Center is writing an article about this work. The article will be available next week.

‘Revealing the atomic restructuring of Pt-Co nanoparticles,’ H. , S. Alayoglu, R. Tao, A. Genc, C.-M. Wang, L. Kovarik, E. Stach, L.-W. Wang, M. Salmeron, G. Somorjai, and H. Zheng. Nano Lett. (2014), DOI: 10.1021/nl500553a