skip to main content

DOE PAGESDOE PAGES

This content will become publicly available on October 25, 2018

Title: Segregation Phenomena in Size-Selected Bimetallic CuNi Nanoparticle Catalysts

Surface segregation, restructuring, and sintering phenomena in size-selected copper–nickel nanoparticles (NPs) supported on silicon dioxide substrates were systematically investigated as a function of temperature, chemical state, and reactive gas environment. Using near-ambient pressure (NAP-XPS) and ultrahigh vacuum X-ray photoelectron spectroscopy (XPS), we showed that nickel tends to segregate to the surface of the NPs at elevated temperatures in oxygen- or hydrogen-containing atmospheres. It was found that the NP pretreatment, gaseous environment, and oxide formation free energy are the main driving forces of the restructuring and segregation trends observed, overshadowing the role of the surface free energy. The depth profile of the elemental composition of the particles was determined under operando CO 2 hydrogenation conditions by varying the energy of the X-ray beam. The temperature dependence of the chemical state of the two metals was systematically studied, revealing the high stability of nickel oxides on the NPs and the important role of high valence oxidation states in the segregation behavior. Atomic force microscopy (AFM) studies revealed a remarkable stability of the NPs against sintering at temperatures as high as 700 °C. The results provide new insights into the complex interplay of the various factors which affect alloy formation and segregation phenomenamore » in bimetallic NP systems, often in ways different from those previously known for their bulk counterparts. In conclusion, this leads to new routes for tuning the surface composition of nanocatalysts, for example, through plasma and annealing pretreatments.« less
Authors:
 [1] ;  [1] ;  [1] ; ORCiD logo [2] ;  [1] ;  [1] ; ORCiD logo [3] ; ORCiD logo [4]
  1. Ruhr Univ. Bochum, Bochum (Germany)
  2. Univ. of Central Florida, Orlando, FL (United States)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States)
  4. Ruhr Univ. Bochum, Bochum (Germany); Univ. of Central Florida, Orlando, FL (United States); Fritz-Haber Institute of the Max Planck Society, Berlin (Germany)
Publication Date:
Report Number(s):
BNL-203649-2018-JAAM
Journal ID: ISSN 1520-6106
Grant/Contract Number:
SC0012704
Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry
Additional Journal Information:
Journal Volume: 122; Journal Issue: 2; Journal ID: ISSN 1520-6106
Publisher:
American Chemical Society
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY
OSTI Identifier:
1437441