A simple eco-friendly solution phase reduction method for the synthesis of polyhedra platinum nanoparticles with high catalytic activity for methanol electrooxidation

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Abstract
The conventional hydrogen gas reduction method for preparation of platinum nanoparticles is to bubble H2 gas into solution with a pre-existing platinum precursor. In this work, instead of bubbling hydrogen gas into Pt precursor solution, we reverse the addition sequence by quickly injecting the Pt precursor into a solution saturated with hydrogen gas. Colloidal Pt nanoparticles thus synthesized are polyhedra of different shapes. Carbon-supported Pt catalysts (Pt-1/C) are prepared by subsequently harvesting the Pt colloids and testing for the methanol oxidation reaction at room temperature. Transmission electron microscope (TEM) images are used to observe the Pt nanoparticle morphology and UV-vis spectra are used to monitor Pt precursor reduction with time. The Pt loadings are confirmed by thermogravimetric analysis. Interestingly, CO stripping cyclic voltammetry of Pt-1/C displayed double oxidation peaks with comparable intensities, one of which is 120 mV more negative than that of a typical CO oxidation peak on Pt. Besides the improved CO tolerance, Pt-1/C easily surpasses the mass activity of Pt/C from E-TEK by 55%. The method reported in this work presents a simple and eco-friendly route for producing carbon-supported platinum electrocatalysts with enhanced CO tolerance and mass activity.

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