| Summary: | 碩士 === 南台科技大學 === 化學工程系 === 92 === Abstract
Pt/Ru alloy, Pt ,and Ru nanoparticles were prepared in reverse micellar solution. The process employed H2PtCl6/RuCl3 as the precursors, NaBH4 as the reductant, water as the dispersion phase, sodium di-2-ethylhekye sulfosuccinate（AOT）as the surfactant ,and isooctane as the continuous phase. The resultant nanoparticles were examined by TEM, showing that their size was about 2~4nm. The composition of the Pt/Ru alloy nanoparticles did not affected their size. In addition, it was found that the surface composition of the Pt/Ru alloy nanoparticles was almost equal to that of their preparation solution, indicating they had a homogeneous alloy phase.
The nanostructured electrodes were prepared by electropheretic deposition of the naonparticles on Ti supports by applying a potential field of 1000 V/cm, followed by a heat treatment in air. It was found that too high heat treatment temperature would decrease the activity of the electrodes towards methanol oxidation, while too low heat treatment temperature would weaken adhesion between nanopartocles and the Ti support. The optimum temperature, in this study, was found to be 550℃.The resultant electrodes were characterized by SEM and AFM, indicating that they had nanostructured surface morphology.
In this investigation, we prepared nanostructured Pt/Ru alloy electrodes, nanostructured Pt +Ru co-deposition electrodes, and nanostructured Pt electrodes；then compared their electrochemical activities towards methanol oxidation in 0.1 M CH3OH+1.0M H2SO4 aqueous solution.
The result from cyclic voltammetly, CV, showed that the current density of the nanostructured Pt/Ru alloy electrode towards methanol oxidation increased first with increasing Ru content of the electrode;then decreased after, reaching maximum at 60 at% Ru. Based on the peak (P1) current density, the nanostructured Pt/Ru alloy electrode with 60at% Ru, Ru 2.2 times as active as the nanostructured Pt+Ru co-deposition electrode with 60at%, 51.3 times as active as the nanostructured Pt electrode, and 224 times as active as the bulk Pt electrode.
The results about the onset potential for methanol oxidation were similar for both the nanostructured Pt/Ru alloy electrode and the nanostructured Pt + Ru co-deposition electrode. This means their onset potential first decreased with increasing Ru content, and then increased after reaching a minimum. The minimum onset potential occurred at 60at% Ru for both the nanostructured Pt +Ru co-deposition electrode.
The potential of the electrodes was held at 0.9V;then relation between the current density for methanol oxidation and reaction time was examed, an approach called j-t method. The results from the j-t method were similar for both the naonstructured Pt/Ru alloy electrode and the nanostructured Pt + Ru co-deposition electrode. This means their initial current densities, j value at t = 0.05sec, first increased with increased Ru content; then decreased after reaching a maximum at 60at% Ru. The initial current densities for the naonstructured Pt/Ru alloy electrode with 60at% Ru and the nanostructured Pt +Ru co-deposition electrode were 40.75 mA/cm2 and 13.01 mA/cm2, respectively. Based on the initial current density, the naonstructured Pt/Ru alloy electrode with 60 at% Ru were 3.1 times as active as the nanostructured Pt + Ru co-deposition electrode with 60 at% Ru, 66.7 times as active as the nanostructured Pt electrode, and 608 times as active as bulk Pt electrode.
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