Suppression of methanol crossover for DMFC using a layer of active catalyst dispersed in the PEM surfaces

• Main Authors: Bing-Jian Su, 蘇竝堅
• Other Authors: Chieh-Hao Wan
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/38085678671908758458

碩士 === 明道大學 === 材料暨系統工程研究所 === 96 === One of the most serious problems of direct methanol fuel cells (DMFCs) is methanol crossover, which not only reduce the efficiency and open circuit voltage of the cells, but also causes significant voltage loss and waste of fuel. The methanol crossed through the membrane also increased the over potential of cathode due to mixed potential of cathode with oxygen. Thus, it is very important to find a better strategy to overcome it. In this study, four group of high activity alloy were chosen. The ternary alloy and quaternary alloy catalysts at PEM anode side was prepared as methanol filter by impregnation-reduction (IR) method. In this method, the catalyst was directly deposited onto a polymer electrode membrane by the IR method. It is expected to enhance DMFCs performance and suppress methanol crossover by this designed. The microstructures, compositions and thickness of the catalysts were characterized by SEM, EDS and XRD, and the metal loading was analyzed by TGA. Then, the best catalysts were found by electrochemistry test, and methanol crossover was monitored by CO2 sensor. It was demonstrated that ternary alloy catalyst (Pt61Ru30Os9) and quaternary alloy catalyst (Pt45Ru38Os10Ir7) of anode can be directly deposited onto a PEM from SEM, EDS and XRD results. Experimental results reveal that catalysts prepared by IR method shows higher electrocatalytic activity of methanol, and can give a better cell performance. It was found that the catalyst can increase the current of DMFC density about 16%, and also can decline the methanol crossover to 46% when operated at cell temperature of 80℃ and anode fuel of 2M methanol.