Variable temperature TEM mapping of the thermodynamically stable element distribution in bimetallic Pt-Rh nanoparticles.

We report here the first variable temperature transmission electron microscopy (TEM) study on smaller Pt-Rh nanoparticles (≤24 nm) under vacuum conditions. Well-defined 50 at% Pt/50 at% Rh Pt-Rh solid solution and Rh(core)-Pt(shell) nanoparticles, obtained colloidal synthesis routes, were investigated between room temperature and 650 °C to elucidate the tendency of elemental mixing/segregation. Key findings are that Pt-Rh nanoparticles <13 nm are stable in a solid solution configuration over the entire studied temperature range, whereas nanoparticles >13 nm tend to segregate upon cooling.

Innovative approach to controlled Pt-Rh bimetallic nanoparticle synthesis.

Precise control of the elemental composition and distribution in bimetallic nanoparticles is of great interest for both fundamental studies and applications, in catalysis. We present a new innovative and facile synthesis strategy for the production of true solid solution Pt Rh nanoparticles. This constitutes a development of the established heat-up method, where undesired shell formation is fully suppressed, despite utilizing metal precursors with different reaction rates.