Synthesis of Pt-Rich@Pt-Ni alloy core-shell nanoparticles using halides

Abstract

We demonstrated the synthesis of Pt-Ni alloy core-shell nanoparticles (NPs) via a one-pot thermal decomposition method, optimized by variation of the concentration of cetyltrimethylammonium chloride (CTAC) and reaction time. The samples prepared without CTAC and in 30 mM CTAC at 250 degrees C for 180 min exhibited the formation of single Pt-rich phases between metallic phases. With increasing CTAC concentrations (60-120 mM) at a constant temperature and time (250 degrees C for 180 min), the products contained both Pt-rich and Pt-Ni alloy phases, consisting of a Pt-rich core with a Pt-Ni alloy shell (Pt-rich@Pt-Ni), in contrast to the single Pt-rich phases prepared at low concentrations or in the absence of CTAC. As the reaction time increased from 10 to 180 min in 60 mM CTAC at 250 degrees C, the Pt-rich NPs were observed to grow in the initial stage, i.e. until a critical reaction time of 60 min, with subsequent formation of the Pt-Ni alloy phase on top of the as-formed Pt-rich NPs. The morphology and structure of the as-prepared NPs were characterized using TEM, EDX and XRD.