Shape-Controlled Platinum Nanoparticles of Different Sizes and Their Electrochemical Properties

Abstract

Platinum (Pt) nanoparticles with controlled shapes and sizes were prepared from a solution of K2PtCl4 in the presence of polyacrylic acid (PAA) as a capping reagent. The effect of temperature, pH, and PAA concentration on the shape, size, and stability of the nanoparticles were investigated. Cubic Pt nanoparticles of different sizes in the range of 4.4–14 nm and cuboctahedral nanoparticles of an average size of 14 nm were obtained. The cubic and cuboctahedral Pt nanoparticles showed strong features of Pt {1 0 0} faces and Pt {1 0 0} and Pt {1 1 1} faces, respectively, on their cyclic voltammograms under argon atmosphere, respectively. Rotating ring disk electrode measurements in O2-saturated H2SO4 solution revealed that the catalytic activity for oxygen reduction reaction (ORR) of cubic Pt nanoparticles (average size 10 nm) was higher than that of cuboctahedral Pt nanoparticles (average size 14 nm). The activity for ORR of both cubic and cuboctahedral Pt nanoparticles decreased slightly after polycrystallization by repeated potential cycling in the range of 0.05 to 1.4 V.