Electrooxidation Of Methanol On Upd-Ru And/or Upd-Sn Modified Pt Electrodes

Recently developed direct methanol fuel cell (DMFC) has been received widespread attention due to the abundant source, the low price, the safety of the storage transportation of the fuel. However, some problems, such as low electrocatalytic activity of the anodic catalyst restrict its practical use.In this thesis, in order to reducing the amount of the Pt catalyst and improving the electricatalytic activity of the Pt catalysts,the under potential deposition method were used to prepare the Ru/Pt Sn/Pt RuSn/Pt catalysts.The electrocatalytic activities for the methanol oxidation were evaluated with the electrochemical techniques. The main results obtained are as follows:Ru can be deposited to Pt surface by under-potential deposition. The effect of Ru on methanol oxidation is independent of whether Ru alloyed with Pt or not, but lies in the distribution of Ru on Pt surface. Ru adatoms on Pt surface can markedly enhance the methanol oxidation on platinum. The results showed that with 7 at % Ru on Pt surface obtained by upd displayed the most catalytic activity for methanol oxidation.Upd-Sn was also investigated for enhancing methanol oxidation on Pt electrodes. The onset potential on upd-Sn modified Pt electrode shifts about 0.25V toward the negative potential in comparison with that on the Pt electrode. It was found that the enhancing effects of tin are subject to the potential range, beyond which, the enhancing effects of tin would disappear. As a matter of fact, The improvement of upd Sn adatoms for the oxidation of methanol occurs in a potential range of 0.1～0.4 V vs Ag/AgCl. In a potential range of 0.4～0.8 V vs Ag/AgCl, the presence of Sn on Pt exhibit a inhibiting role to methanol oxidation.The different effect of Sn and Ru encouraged raise an interesting topic, what would be if Pt electrode was modified by upd-Ru and upd-Sn simultaneously? Can we expect a synergetic effect contributed by Ru and Sn. The oxidation of methanol on upd-RuSn/Pt starts as early as on upd-Sn/Pt and the oxidative current is even higher than on upd-Sn/Pt in lower potential range ca. 0.15 V～0.32 V. In potential range ca. 0.3 V～0.45V, the oxidative current on upd-RuSn/Pt is higher than that on pure Pt and upd-Sn/Pt electrode due to the presence of Ru. Although the mechanism of this ternary catalyst is not clear, it is undisputable that some synergetic effect of Sn and Ru did occur.