Efficiency Enhancement of Methanol/Ethanol Oxidation Reactions on Pt Nanoparticles Prepared Using a New Surfactant, 1,1-Dimethyl Heptanethiol

Abstract

In this study, carbon-supported platinum nanoparticle catalysts were prepared using PtCl4 and H2PtCl6 as starting materials and 1-heptanethiol, 1,1-dimethyl heptanethiol, 1-hexadecanethiol and 1-octadecanethiol as surfactants. These nanoparticles can be used as catalysts for methanol and ethanol oxidation reactions in methanol and ethanol fuel cells. 1,1-Dimethyl heptanethiol was used for the first time in this type of synthesis; other surfactants were used to synthesize nanoparticles for comparison of the catalyst's performance. Cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy (TEM) were used to characterize the catalysts. It should also be stressed that AFM was employed for the first time in determining the surface topography of these catalysts. XRD, TEM and AFM height results indicate that the platinum crystallizes into a face-centered cubic structure and the surfactant plays an important role in determining the size of the platinum nanoparticles. XPS data revealed that the platinum was found in two different oxidation states, Pt(0) and Pt(IV) with a ratio of about 7.5 : 2.5, respectively. Electrochemical studies showed catalyst IIa to be the most active sample towards methanol/ethanol oxidation reactions (similar to 342 A g(-1) Pt at 0.612 V for methanol (4.6 times more active than the commercial catalyst), similar to 309 A g(-1) Pt at 0.66 V for ethanol, (15.4 times more active than the commercial catalyst)).