Pt_{: X}Ir_yalloy nanoparticles with fully tunable bulk and surface compositions

Pt_xIr_ynanoparticles (NPs) are of great interest, largely due to their wide range of applications in gas phase catalysis, electrocatalysis, sensors, and more. Most of the prior work on Pt_xIr_yNPs, formed using a variety of approaches, has shown that the surface becomes uncontrollably enriched with Pt relative to the NP bulk. In this work, Pt_xIr_yalloy NPs (with x and y (35-85%) being the atomic percent of Pt and Ir, respectively) were synthesized using the simple polyol method, using Pt and Ir solution precursors and employing two sequential heating steps. It is shown that this method prevents the enrichment of the surface with either Pt or Ir, resulting in the same surface and bulk compositions, fully controllable by modifying the ratio of metal precursors in solution. This was confirmed by electrochemical studies, wavelength dispersive X-ray spectroscopy (XRD), and energy dispersive X-ray spectroscopy (EDS) coupled with high resolution transmission electron microscopy (HRTEM), while XRD analysis confirmed Pt_xIr_yalloy formation. The predictable and tunable composition of these materials, both in the NP bulk and at their surfaces, is a novel and important advantage for their future use as catalysts and reagents for a broad range of reactions, including methanol oxidation, as demonstrated here.