Abstract
Reduction reactions in practical bimetallic platinum–cobalt electrode catalyst precursors containing platinum, cobalt and cobalt oxides in hydrogen at 200, 450 and 700 °C for 6 h have been studied in situ using an aberration corrected environmental (scanning) transmission electron microscope (AC
E(S)TEM). Little difference was observed inreduction at 200°C but during and after reduction at 450 °C, small nanoparticles less than 3 nm in diameter with tetragonal PtCo structures were observed and limited Pt3Co ordering could be seen on the surfaces of larger nanoparticles. During and after reduction at 700 °C, fully ordered Pt3Co and PtCo nanoparticles larger than 4 nmwere produced and the average nanoparticle size almost trebled relative to the fresh precursor. After reduction at 450 and 700 °C, most nanoparticles were disordered platinum/cobalt alloys with fcc structure. After reduction at 700 °C many of the smallest nanoparticles disappeared suggesting Ostwald ripening had occurred. Mechanisms concerning the thermal transformation of mixed cobalt and platinum species are discussed, offering new insights into the creation of bimetallic platinum–cobalt nanoparticles in fuel cell catalysts.
E(S)TEM). Little difference was observed inreduction at 200°C but during and after reduction at 450 °C, small nanoparticles less than 3 nm in diameter with tetragonal PtCo structures were observed and limited Pt3Co ordering could be seen on the surfaces of larger nanoparticles. During and after reduction at 700 °C, fully ordered Pt3Co and PtCo nanoparticles larger than 4 nmwere produced and the average nanoparticle size almost trebled relative to the fresh precursor. After reduction at 450 and 700 °C, most nanoparticles were disordered platinum/cobalt alloys with fcc structure. After reduction at 700 °C many of the smallest nanoparticles disappeared suggesting Ostwald ripening had occurred. Mechanisms concerning the thermal transformation of mixed cobalt and platinum species are discussed, offering new insights into the creation of bimetallic platinum–cobalt nanoparticles in fuel cell catalysts.
| Original language | English |
|---|---|
| Pages (from-to) | 143-150 |
| Number of pages | 8 |
| Journal | Journal of Microscopy |
| Volume | 269 |
| Issue number | 2 |
| Early online date | 6 Jul 2017 |
| DOIs | |
| Publication status | Published - Feb 2018 |
Bibliographical note
Funding Information:PLG and EDB thank the EPSRC (UK) for a critical mass research grant EP/J0118058/1 supporting this research and a postdoctoral research assistantship (PDRA) to MRW from the grant. We thank A. Martinez Bonastre and D. Ozkaya for helpful discussions.
Publisher Copyright:
© 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society
Keywords
- Fuel cell catalysts
- In situ electron microscopy
- Nanoparticles