Abstract
Octahedral-shaped PtNi-alloy nanoparticles are highly active oxygen reduction reaction catalysts for the cathode in proton exchange membrane fuel cells. However, one major drawback in their application is their limited long-term morphological and compositional stability. Here, we present a detailed in situ electron microscopy characterization of thermal annealing on octahedral-shaped PtNi catalysts as well as on doped octahedral PtNi(Mo) and PtNi(MoRh) catalysts. The evolution of their morphology and composition was quantified during both ex situ and in situ experiments using energy dispersive X-ray spectroscopy in a scanning transmission electron microscope under a hydrogen atmosphere and in vacuum. Morphological changes upon heating, i.e., a gradual loss of the octahedral shape and a continuous rounding of the particles, were observed, as well as evidence for increased alloying. Furthermore, the evolution of the shape of the PtNi(Mo) nanoparticles was quantified using in situ experiments under hydrogen atmosphere in a transmission electron microscope. The shape change of the particles was quantified using segmentation maps created by a neural network. It has been demonstrated that morphological changes crucially depend on the composition and surface doping: doping with Mo or Mo/Rh significantly stabilizes the structure, allowing for persistence of a truncated octahedral shape during heat treatments.
Original language | English |
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Pages (from-to) | 5959-5967 |
Number of pages | 9 |
Journal | ACS Applied Energy Materials |
Volume | 6 |
Issue number | 11 |
DOIs | |
State | Published - 12 Jun 2023 |
Externally published | Yes |
Bibliographical note
Publisher Copyright:© 2023 American Chemical Society.
Funding
The authors gratefully acknowledge the support of the German Research Society (DFG) for supporting this work under grant numbers STR 596/5-2 and HE 7192/1-2. P.S. acknowledges funding by the German Research Society (DFG) for supporting this work under grant number STR 596/18-1. The research leading to these results has received funding from the European Union’s “Horizon Europe” Clean Hydrogen Partnership research and innovation program under grant agreement no. 101101409, BRAVA, and no. 101101346, HIGHLANDER.
Funders | Funder number |
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Horizon Europe” Clean Hydrogen Partnership research and innovation program | 101101409, 101101346 |
Deutsche Forschungsgemeinschaft | STR 596/5-2, HE 7192/1-2, STR 596/18-1 |
Keywords
- EDX
- STEM
- annealing
- catalyts
- fuel-cells
- in situ