1.7 nm platinum nanoparticles: synthesis with glucose starch, characterization and catalysis.

Monodisperse platinum nanoparticles (PtNPs) were synthesized by a green recipe. Glucose serves as a reducing agent and starch as a stabilization agent to protect the freshly formed PtNP cores in buffered aqueous solutions. Among the ten buffers studied, 2-(N-morpholino)ethanesulfonic acid (MES), ammonium acetate and phosphate are the best media for PtNP size control and fast chemical preparation. The uniform sizes of the metal cores were determined by transmission electron microscopy (TEM) and found to be 1.8 ± 0.5, 1.7 ± 0.2 and 1.6 ± 0.5 nm in phosphate, MES and ammonium acetate buffer, respectively. The estimated total diameter of the core with a starch coating layer is 5.8-6.0 nm, based on thermogravimetric analysis (TGA). The synthesis reaction is simple, environmentally friendly, highly reproducible, and easy to scale up. The PtNPs were characterized electrochemically and show high catalytic activity for reduction of dioxygen and hydrogen peroxide as well as for oxidation of dihydrogen. The PtNPs can be transferred to carbon support materials with little demand for high specific surface area of carbon. This enables utilization of graphitized carbon blacks to prepare well-dispersed Pt/C catalysts, which exhibit significantly improved durability in the accelerated aging test under fuel cell mimicking conditions.