Controlled alloying of Pt-Rh nanoparticles by the polyol approach

We report on a facile synthesis strategy for the reaction matrix platinum(II)-acetylacetonate - rhodium(III)-acetylacetonate - polyvinylpyrrolidone - 1,4-butanediol and show that phase pure Pt-Rh alloyed nanoparticles can be achieved with compositional control based on simultaneous decomposition of Pt-and Rh-metal precursors. By combining data from powder X-ray diffraction, (high-resolution) transmission electron microscopy [(HR)TEM], energy dispersive X-ray spectroscopy (EDS) and kinetic experiments, we describe key parameters for compositional control. Powder X-ray diffraction suggests a crystallite size of around 4 nm, less than the size of polycrystalline particles, of around 7 nm in average and with different morphologies, as imaged by TEM. High-Angle Annular Dark Field Scanning TEM and EDS show some compositional fluctuations between and within in the received Pt-Rh nanoparticles. Based on insight to the reaction kinetics of the individual Pt and Rh metal precursors, recipes are fine-tuned to provide bimetallic nanoparticles with controlled average composition, including achieving the identical Pt/Rh molar ratio for the resulting nanoparticles as defined by the precursor mixture prior to the simultaneous reduction step. The adopted approach adds value beyond the Pt-Rh system and shows that control of precursor reactivity is essential to provide exact metal compositions of bimetallic nanoparticles for use in fundamental studies and applications. (C) 2018 Elsevier B.V. All rights reserved.