Synthesis and electrocatalytic activity of photoreduced platinum nanoparticles in a poly(ethylenimine) matrix.

Monodisperse polymer-mediated platinum (Pt) nanoparticles (NPs) have been synthesized by photoreduction in the presence of poly(ethylenimine) (PEI), a hyperbranched polymer. The formation process of the Pt NPs is pursued by UV-vis spectroscopy, and the formation mechanism is discussed. The morphology and size of the Pt NPs were characterized by transmission electron microscopy (TEM). TEM imaging shows that the Pt NPs' average diameter is 2.88 +/- 0.53 nm. The PEI/Pt NPs were immobilized on glassy carbon electrodes, and the electrocatalytic activity of the catalysts was investigated by cyclic voltammetry. PEI/Pt NPs exhibit very high catalytic activity for a methanol oxidation reaction. PEI/Pt NPs on glassy carbon electrodes are robust, showing good tolerance to poisoning even after many cycles. The electrocatalytic activity of PEI/Pt NPs compares favorably with other polymer-mediated Pt NPs. The results indicate that PEI is an appropriate complexing reducing agent for the photochemical production of Pt NPs and a good capping agent, allowing immobilization of the NPs on the working electrode.