(547b) Thermal Stability of Shape-Controlled Pd-Pt Core-Shell Nanoparticles

Luke T. Roling^a, Ahmed
O. Elnabawy^a, Madeline Vara^b,
Xue Wang^b,
Younan Xia^b, and Manos Mavrikakis^a

^aDepartment of Chemical
& Biological Engineering, University of Wisconsin-Madison, Madison, WI
^bDepartment of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA

We recently reported the
synthesis and electrocatalytic performance of
shape-controlled Pd-Pt core-shell nanoparticles that
demonstrated exceptional activity and stability toward the oxygen reduction
reaction.^1,2 In this presentation, we investigate and explain the durability
of these catalysts in high-temperature environments typical of a broader range
of catalytic applications. We observe that the cubic and octahedral nanocatalysts are stable to at least 500 °C; interestingly,
the core-shell structure and overall particle shape are each deformed at
different temperatures in the two catalyst geometries.

Detailed DFT calculations rationalize
the observed behaviors, attributing the differences in reconstruction to lower
activation energy barriers for metal atom migration from the nanoparticle
edges. Calculations also indicate that different concentrations of subsurface
vacancies are seeded during nanoparticle synthesis, and that these are responsible
for differences in Pd-Pt interdiffusion,
which causes disruption of the core-shell structure at elevated temperatures.

1. S. Xie, S.-I. Choi, N. Lu, L. T.
Roling, J. A. Herron, L. Zhang, J. Park, J. Wang, M. J. Kim, Z. Xie, M.
Mavrikakis, Y. Xia, Nano Letters 2014, 14, 3570

2. J. Park, L. Zhang, S. Choi, L. T. Roling, N. Lu, J. A. Herron, S. Xie, J.
Wang, M. J. Kim, M. Mavrikakis, Y. Xia, ACS
Nano 2015, 9, 2635.