Anisotropic phase segregation and migration of Ptin nanocrystals en route to nanoframe catalysts
(TOP) The Pt-Ni alloy formed during synthesis begins as Pt-rich, becomes Ni-rich as RD is formed, and then enriches in Pt as time is prolonged. (BOTTOM) Elemental mapping shows distribution of the elements in nanocrystals at various stages of the synthesis.
Control of nanoscopic segregation of the elements in Pt-Ni rhombic dodecahedra (RD) was discovered to create a 3-D Pt3Ni nanoframe
Significance and Impact
Being able to control the element spatial distribution within nanocrystals is an advanced strategy for obtaining catalysts with new morphologies and structure
- Initial Pt-rich alloy grows in <111> and <200> directions, providing compositional anisotropy
- Pt segregates to axes of RD such that when Ni-rich phase is corroded, tetradecapod (14 arm) structure is obtained
- Pt migrates to edges of RD after certain time such that when Ni-rich phase is corroded, nanoframe can be obtained