TY  - JOUR
AU  - Beermann, Vera
AU  - Gocyla, Martin
AU  - Kühl, Stefanie
AU  - Padgett, Elliot
AU  - Schmies, Henrike
AU  - Goerlin, Mikaela
AU  - Erini, Nina
AU  - Shviro, Meital
AU  - Heggen, Marc
AU  - Dunin-Borkowski, Rafal
AU  - Muller, David A.
AU  - Strasser, Peter
TI  - Tuning the Electrocatalytic Oxygen Reduction Reaction Activity and Stability of Shape-Controlled Pt–Ni Nanoparticles by Thermal Annealing − Elucidating the Surface Atomic Structural and Compositional Changes
JO  - Journal of the American Chemical Society
VL  - 139
IS  - 46
SN  - 1520-5126
CY  - Washington, DC
PB  - American Chemical Society
M1  - FZJ-2018-00779
SP  - 16536 - 16547
PY  - 2017
AB  - Shape-controlled octahedral Pt–Ni alloy nanoparticles exhibit remarkably high activities for the electroreduction of molecular oxygen (oxygen reduction reaction, ORR), which makes them fuel-cell cathode catalysts with exceptional potential. To unfold their full and optimized catalytic activity and stability, however, the nano-octahedra require post-synthesis thermal treatments, which alter the surface atomic structure and composition of the crystal facets. Here, we address and strive to elucidate the underlying surface chemical processes using a combination of ex situ analytical techniques with in situ transmission electron microscopy (TEM), in situ X-ray diffraction (XRD), and in situ electrochemical Fourier transformed infrared (FTIR) experiments. We present a robust fundamental correlation between annealing temperature and catalytic activity, where a ∼25 times higher ORR activity than for commercial Pt/C (2.7 A mgPt–1 at 0.9 VRHE) was reproducibly observed upon annealing at 300 °C. The electrochemical stability, however, peaked out at the most severe heat treatments at 500 °C. Aberration-corrected scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy (EDX) in combination with in situ electrochemical CO stripping/FTIR data revealed subtle, but important, differences in the formation and chemical nature of Pt-rich and Ni-rich surface domains in the octahedral (111) facets. Estimating trends in surface chemisorption energies from in situ electrochemical CO/FTIR investigations suggested that balanced annealing generates an optimal degree of Pt surface enrichment, while the others exhibited mostly Ni-rich facets. The insights from our study are quite generally valid and aid in developing suitable post-synthesis thermal treatments for other alloy nanocatalysts as well.
LB  - PUB:(DE-HGF)16
C6  - pmid:29019692
UR  - <Go to ISI:>//WOS:000416496400025
DO  - DOI:10.1021/jacs.7b06846
UR  - https://juser.fz-juelich.de/record/842560
ER  -