Dendrimers as nanoreactors to produce platinum nanoparticles embedded in layer-by-layer films for methanol-tolerant cathodes

Abstract

We report on the fabrication of layer-by-layer (LbL) films of PAMAM dendrimers incorporating platinum nanoparticles (Pt-PAMAM) alternated with poly(vinylsulfonic acid) (PVS). Pt-PAMAM structures were obtained via chemical reduction of H₂PtCl₆ in the presence of PAMAM, using formic acid as reducing agent. An average particle size of 3 nm was estimated using the Scherrer equation with the X-ray diffractograms in multilayer films, which was confirmed with transmission electron microscopy (TEM) for a Pt-PAMAM layer. The formation of Pt nanoparticles was monitored with UV–Vis spectroscopy by measuring the decrease in the band intensity at 375 nm, assigned to the electronic absorption from ${\mathrm{PtCl}}_6^{2-}$ <!--mathContainer--> <!--Loading Mathjax--> ions. These LbL films were proven fully tolerant to methanol oxidation for potentials below 1.0 V. As a proof of principle, we show that the electrochemical response for the Pt-PAMAM LbL films is characteristic of platinum, regardless of the presence of methanol in the electrolytic solution. The discovery of a methanol-tolerant electrode in Pt-PAMAM LbL films may represent a major breakthrough for further developments in methanol fuel cells, since methanol crossover through the membrane is one of the most important drawbacks of direct-methanol fuel cells.