自呼吸式直接甲醇燃料电池性能及其传质特性

Performance and mass transfer characteristics of an air-breathing DMFC

针对有效面积为1cm2的自呼吸式直接甲醇燃料电池(direct methanol fuel cell,DMFC)单电池,阳极采用燃料罐供液,将阴极侧集流体和夹具设计为一体式结构,并用自制的七合一膜电极组件对其进行测试,讨论了催化剂类型、扩散层材料、集流体结构等因素对其性能的影响,分析了电池内部的传质特性,优化了电池特别是其在中高电流密度条件下的性能。实验结果表明:采用Pt黑、Pt-Ru黑催化剂制作的自呼吸式DMFC能强化反应物的传质;采用碳布制作的膜电极更倾向于获得更高的极限电流密度;低电流密度时,因甲醇渗透电池电压随着甲醇浓度的增加而降低,但在中高电流密度下,电池性能随甲醇浓度的增大先升高后降低;平行集流体有利于阴阳极生成物的排出和反应物的传质,因此易获得较高的电池性能。

A single air-breathing direct methanol fuel cell （DMFC） with an active area of 1 cm^2 was fabricated and investigated experimentally. A fuel reservoir in anode was used to supply methanol solution. A cathode current collector was designed to integrate the cathode fixture. The fuel cell with a home-made membrane electrode assembly （MEA） was tested. Effects of catalyst type, diffusion layer material, current collector structure and other factors on the cell performance were discussed. The mass transfer characteristics in the fuel cell were also analyzed. Performance of the air-breathing DMFC was optimized especially at high current densities. The results showed that the mass transfer of reactants could be enhanced by using Pt black or Pt-Ru black catalyst. A higher limit current density could be obtained by using carbon cloth as the gas diffusion layer. At low current densities, the cell voltage decreased with an increase in methanol concentration due to the methanol crossover. However, at middle and high current densities, the cell performance increased firstly and then decreased with methanol concentration. The parallel current collector benefits the removal of resultants and the mass transfer of reactants both at the anode and the cathode. Thus, a better cell performance could be achieved by using parallel current collectors.