Polyelectrolyte-stabilized Pt nanoparticles as new electrocatalysts for low temperature fuel cells

Polyelectrolyte-stabilized Pt nanoparticles were synthesized by ethanol reduction of Pt salt (H2PtCl6) in the presence of ionic polyelectrolyes such as poly(diallyldimethylammonium chloride) (PDDA), poly(allylamine hydrochloride) (PAH), poly(sodium 4-styrenesulfonate) (PSS), Nafion, poly(acrylic acid) (PAA), poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMP) and non-ionic polymer, poly(vinylpyrrolidone) (PVP). The formation, size and distribution of polyelectrolyte-stabilized Pt nanoparticles (Pt NPs) were characterized by UV–vis absorption spectrum and transmission electron microscopy (TEM). Polyelectrolyte-stabilized Pt NPs have a particle size range of 2–4 nm, however, they show significantly different electrochemical activities for the methanol oxidation and oxygen reduction reactions. The best electrocatalytic activities were observed on PDDA–Pt and PSS–Pt NPs which also showed better electrocatalytic activity than that of the commercial Pt black catalysts. The results indicate the significant enhancing effect of the NH4+ and SO3- end groups of the polyelectrolytes on the electrocatalytic activities of Pt NPs for polymer electrolyte membrane fuel cells.