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Ni‐Catalyzed Growth of Graphene Layers during Thermal Annealing: Implications for the Synthesis of Carbon‐Supported PtNi Fuel‐Cell Catalysts
Author(s) -
Gan Lin,
Rudi Stefan,
Cui Chunhua,
Strasser Peter
Publication year - 2013
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201300235
Subject(s) - sintering , bimetallic strip , materials science , catalysis , annealing (glass) , chemical engineering , graphene , alloy , nanoparticle , particle size , metallurgy , nanotechnology , metal , chemistry , organic chemistry , engineering
Thermal annealing is an important and widely adopted step during the synthesis of Pt bimetallic fuel‐cell catalysts, although it faces the inevitable drawback of particle sintering. Understanding this sintering mechanism is important for the future development of highly active and robust fuel‐cell catalysts. Herein, we studied the particle sintering during the thermal annealing of carbon‐supported Pt 1– x Ni x (PtNi, PtNi 3 , and PtNi 5 ) nanoparticles, a reported recently class of highly active fuel‐cell catalysts. By using high‐resolution transmission electron microscopy, we found that annealing at an intermediate temperature (400 °C) effectively increased the extent of alloying without particle sintering; however, high‐temperature annealing (800 °C) caused severe particle sintering, which, unexpectedly, was strongly dependent on the composition of the alloy, thus showing that a higher Ni content resulted in a higher extent of particle sintering. This result can be ascribed to the solid‐state transformation of the carbon support into graphene layers, catalyzed by Ni‐richer catalyst, which, in turn, promoted particle migration/coalescence and, hence, more‐significant sintering. Therefore, our results provide important insight for the synthesis of carbon‐supported Pt‐alloy fuel‐cell catalysts.