Bimetallic catalysts can undergo segregation or redistribution of the metals driven by oxidizing and reducing environments. Bragg coherent diffraction imaging (BCDI) was used to relate displacement fields to compositional distributions in crystalline Pt-Rh alloy nanoparticles. Three-dimensional images of internal composition showed that the radial distribution of compositions reverses partially between the surface shell and the core when gas flow changes between O2 and H2. Our observation suggests that the elemental segregation of nanoparticle catalysts should be highly active during heterogeneous catalysis and can be a controlling factor in synthesis of electrocatalysts. In addition, our study exemplifies applications of BCDI for in situ 3D imaging of internal equilibrium compositions in other bimetallic alloy nanoparticles.
Bibliographical noteFunding Information:
Bragg coherent diffraction imaging x-ray measurements and data analysis was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences Engineering Division. Use of the Advanced Photon Source was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The work at DESY, x-ray measurements, sample preparation, and marker-based nanotransfer, was supported by the EU-H2020 research and innovation program under Grant Agreement No. 654360 NFFA-Europe (T. F. K., H. R., C. S., A. S.) and the Helmholtz Associations Initiative and Networking Fund and the Russian Science Foundation, Grant No. HRSF-0002 (L. G., Y. Y. K., I. A. V.). The use of the FIB dual beam instrument granted by BMBF (5K13WC3, PT-DESY) is acknowledged. We thank S. Kulkarni and A. Jeromin (DESY NanoLab ) for marking the regions of interest by IBID/EBID and the SEM postanalysis. One of the authors (T. K.) thanks the Japanese Society for the Promotion of Science (JSPS) for JSPS Postdoctoral Fellowships for Research Abroad.
© 2019 American Physical Society.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)