posted on 2021-07-20, 18:06authored byPeng-Cheng Chen, Mengyu Gao, Sunmoon Yu, Jianbo Jin, Chengyu Song, Miquel Salmeron, Mary C. Scott, Peidong Yang
Phase-separation is commonly observed
in multimetallic nanomaterials,
yet it is not well understood how immiscible elements distribute in
a thermodynamically stable nanoparticle. Herein, we studied the phase-separation
of Au and Rh in nanoparticles using electron microscopy and tomography
techniques. The nanoparticles were thermally annealed to form thermodynamically
stable structures. HAADF-STEM and EDS characterizations reveal that
Au and Rh segregate into two domains while their miscibility is increased.
Using aberration-corrected HAADF-STEM and atomic electron tomography,
we show that the increased solubility of Au in Rh is achieved by forming
Au clusters and single atoms inside the Rh domains and on the Rh surface.
Furthermore, based on the three-dimensional reconstruction of a AuRh
nanoparticle, we can visualize the uneven interface that is embedded
in the nanoparticle. The results advance our understanding on the
nanoscale thermodynamic behavior of metal mixtures, which is crucial
for the optimization of multimetallic nanostructures for many applications.