The preparation and characterization of nano-sized Pt-Pd/C catalysts and comparison of their superior catalytic activities for methanol and ethanol oxidation

摘要

In this study, two groups of carbon supported PtPd samples with different percentages of metals were prepared to examine the effects of Pd and stabilizing agents on the catalytic activity towards methanol and ethanol oxidation reactions. As a stabilizing agent, 1-hexanethiol and 1,1-dimethyl hexanethiol were used for group "a" and "b" catalysts, respectively. Cyclic voltammetry, chronoamperometry, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy (XPS) were employed to understand the nature of the prepared catalysts. TEM and XRD results indicated a similar size distribution of the metal nanoparticles with a narrow average crystallite size of 3.0-3.7 nm. XPS data revealed the presence of two different oxidation states for both platinum and palladium, being Pt(0), Pt(IV), Pd(0), and Pd(II). Electrochemical studies indicated that the group β type catalysts have a higher catalytic activity than group α The most active catalyst was found to be a carbon supported 88 %Pt/12 %Pd prepared with 1,1- dimethyl hexanethiol, which has an activity of ?5 times (?0.450 A/mg Pt at 0.57 V for methanol) and ?14 times (?0.350 A/g Pt at 0.56 V for ethanol) greater than the commercial E-TEK catalyst.