Synthesis and Structural Evolution of Nickel-Cobalt Nanoparticles Under H2 and CO2.
Bimetallic nanoparticle (NP) catalysts are interesting for the development of selective catalysts in reactions such as the reduction of CO2 by H2 to form hydrocarbons. Here the synthesis of Ni-Co NPs is studied, and the morphological and structural changes resulting from their activation (via oxidation/reduction cycles), and from their operation under reaction conditions, are presented. Using ambient-pressure X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and transmission electron microscopy, it is found that the initial core-shell structure evolves to form a surface alloy due to nickel migration from the core. Interestingly, the core consists of a Ni-rich single crystal and a void with sharp interfaces. Residual phosphorous species, coming from the ligands used for synthesis, are found initially concentrated in the NP core, which later diffuse to the surface.
Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
Sophie
S
Carenco
Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.|Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
Cheng-Hao
CH
Wu
Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.|Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
Andrey
A
Shavorskiy
Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
Selim
S
Alayoglu
Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.|Department of Chemistry, University of California Berkeley, Berkeley, CA, 94720, USA.
Gabor A
GA
Somorjai
Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
Hendrik
H
Bluhm
Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.|Department of Materials Sciences and Engineering, University of California Berkeley, Berkeley, CA, 94720, USA.
Miquel
M
Salmeron
ambient-pressure X-ray photoelectron spectroscopy; bimetallic nanoparticles; in situ characterization; nanoalloys