Back to Search Start Over

Revealing the atomic ordering of binary intermetallics using in situ heating techniques at multilength scales.

Authors :
Yin Xiong
Yao Yang
Rui Zeng
DiSalvo, Francis J.
Abruña, Héctor D.
Xin Huang
Joress, Howie
Agyeman-Budu, David N.
Brock, Joel D.
Padgett, Elliot
Muller, David A.
Gupta, Unmukt
Escobedo, Fernando A.
Yarlagadda, Venkata
Moylan, Thomas E.
Anusorn Kongkanand
Source :
Proceedings of the National Academy of Sciences of the United States of America; 2/5/2019, Vol. 116 Issue 6, p1974-1983, 10p
Publication Year :
2019

Abstract

Ordered intermetallic nanoparticles are promising electrocatalysts with enhanced activity and durability for the oxygen-reduction reaction (ORR) in proton-exchange membrane fuel cells (PEMFCs). The ordered phase is generally identified based on the existence of superlattice ordering peaks in powder X-ray diffraction (PXRD). However, after employing a widely used postsynthesis annealing treatment, we have found that claims of "ordered" catalysts were possibly/likely mixed phases of ordered intermetallics and disordered solid solutions. Here, we employed in situ heating, synchrotron-based, X-ray diffraction to quantitatively investigate the impact of a variety of annealing conditions on the degree of ordering of large ensembles of Pt3Co nanoparticles. Monte Carlo simulations suggest that Pt3Co nanoparticles have a lower order-disorder phase transition (ODPT) temperature relative to the bulk counterpart. Furthermore, we employed microscopic-level in situ heating electron microscopy to directly visualize the morphological changes and the formation of both fully and partially ordered nanoparticles at the atomic scale. In general, a higher degree of ordering leads to more active and durable electrocatalysts. The annealed Pt3Co/C with an optimal degree of ordering exhibited significantly enhanced durability, relative to the disordered counterpart, in practical membrane electrode assembly (MEA) measurements. The results highlight the importance of understanding the annealing process to maximize the degree of ordering in intermetallics to optimize electrocatalytic activity. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00278424
Volume :
116
Issue :
6
Database :
Complementary Index
Journal :
Proceedings of the National Academy of Sciences of the United States of America
Publication Type :
Academic Journal
Accession number :
134589541
Full Text :
https://doi.org/10.1073/pnas.1815643116