Abstract
Platinum is the primary catalyst for many chemical reactions in the field of heterogeneous catalysis. However, platinum is both expensive and rare. Therefore, it is advantageous to combine Pt with another metal to reduce cost while also enhancing stability. To that end, Pt is often combined with Co to form Co-Pt nanocrystals. However, dynamical restructuring effects that occur during reaction in Co-Pt ensembles can impact catalytic properties. In this study, model Co2Pt3 nanoparticles supported on carbon were characterized during a redox cycle with two in situ approaches, namely, X-ray absorption spectroscopy (XAS) and scanning transmission electron microscopy (STEM) using a multimodal microreactor. The sample was exposed to temperatures up to 500 °C under H2, and then to O2 at 300 °C. Irreversible segregation of Co in the Co2Pt3 particles was seen during redox cycling, and substantial changes of the oxidation state of Co were observed. After H2 treatment, a fraction of Co could not be fully reduced and incorporated into a mixed Co-Pt phase. Reoxidation of the sample increased Co segregation, and the segregated material had a different valence state than in the fresh, oxidized sample. This in situ study describes dynamical restructuring effects in CoPt nanocatalysts at the atomic scale that are crucial to understand in order to improve the design of catalysts used in major chemical processes.
| Original language | English |
|---|---|
| Pages (from-to) | 20619-20632 |
| Number of pages | 14 |
| Journal | ACS Nano |
| Volume | 15 |
| Issue number | 12 |
| DOIs | |
| State | Published - Dec 28 2021 |
| Externally published | Yes |
Funding
This work was primarily supported as part of the Integrated Mesoscale Architectures for Sustainable Catalysis (IMASC), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award #DE-SC0012573. This research used 4-BM (XFM) beamline of the National Synchrotron Light Source, a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory (BNL) under Contract No. DE-SC0012704. This work was carried out in part at the Singh Center for Nanotechnology, which is supported by the NSF National Nanotechnology Coordinated Infrastructure Program under grant NNCI-2025608. Additional support to the Nanoscale Characterization Facility at the Singh Center has been provided by the Laboratory for Research on the Structure of Matter (MRSEC) supported by the National Science Foundation (DMR-1720530). Nanoparticle synthesis and preparation was supported as part of the Catalysis Center for Energy Innovation, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001004. The authors would like to thank H. T. Ngan, G. Yan and P. Sautet for providing the stability diagram of Co oxides in Figure S12 . The authors also would like to thank S. Nicholas for her help at the 4-BM beamline.
| Funders | Funder number |
|---|---|
| Catalysis Center for Energy Innovation | |
| Laboratory for Research on the Structure of Matter | |
| National Science Foundation | DMR-1720530, NNCI-2025608 |
| U.S. Department of Energy | |
| Office of Science | |
| Basic Energy Sciences | -SC0012573, DE-SC0001004 |
| Brookhaven National Laboratory | DE-SC0012704 |
| Materials Research Science and Engineering Center, Harvard University |
Keywords
- atomic resolution
- bimetallic structures
- Co-Pt nanocatalysts
- dynamical restructuring effects
- in situ STEM-EELS
- in situ XAS