以膠體先驅物法製備之Pt/C和PtRu/C陽極觸媒電催化活性之研究

Abstract

本研究以膠體先驅物法開發低溫燃料電池用的碳黑負載的鉑(Pt)與鉑釕(PtRu)合金陽極觸媒，並以循環伏安法及旋轉電極探討Pt/C與PtRu/C觸媒電極上一氧化碳的吸附和其吸附對氫氣氧化反應的影響。使用原料為PtCl2、RuCl3與N(oct4)[Bet3H]，製備所得的5.4~27.2wt% Pt/C與6.5~26.6wt% PtRu/C觸媒之Pt和PtRu粒徑，以X-ray繞射分析儀和穿透式顯微鏡量測，範圍分別為3.1~8.9 nm與2.6~3.3 nm，其值比商用Pt/C與PtRu/C觸媒中的略大。本研究藉由一氧化碳吸附降低觸媒活性面積，利用旋轉電極方法求得Pt/C與PtRu/C觸媒層氫氣氧化的電流密度，並進而測得交換電流密度。在 28℃下於0.5M H2SO4中測得之Pt/C和PtRu/C的交換電流密度分別為5mAcm-2 和1.4mAcm-2。Pt/C對氫氣氧化的電催化活性比PtRu/C好，但前者吸附一氧化碳的速率比後者快。 本研究的結果有助於開發抗一氧化碳毒化的含鉑合金，應用為低溫燃料電池的陽極觸媒材料。

Platinum and platinum-ruthenium alloy catalysts on carbon were prepared by colloidal precursor technique. The adsorption of CO and its effect on the hydrogen oxidation reaction on the catalyst were investigated by cyclic voltammetry (CV) and the rotating disk electrode (RDE) techniques. PtCl2, RuCl3 and N(oct4)[ Bet3H] were used to prepared the catalysts. The particle sizes of Pt and PtRu for 5.4~27.2 wt% Pt/C and 6.5~26.6 wt% PtRu/C prepared, determined by X-ray diffraction and transmission electron microscope, were in the range of 3.1~8.9 nm and 2.6~3.3 nm, respectively, which are slightly larger than those of commercial catalysts. By reducing the electro-active surface area of the catalyst through the adsorption of CO, the current density in the catalyst layer and thus the exchange current density for hydrogen oxidation reaction on the catalyst can be measured using the rotating disk electrode (RDE) method. The exchange current densities of Pt/C and PtRu/C in 0.5M H2SO4 at 28℃ were determined to be 5mAcm-2 and 1.4mAcm-2, respectively. Pt/C had higher electrocatalytic activity for hydrogen oxidation than PtRu/C, but Pt/C was poisioned by CO faster than PtRu/C. The results of this research may contribute to the development of CO-tolerant platinum-based alloy anode catalysts for low-temperature fuel cells.