直接甲醇燃料电池中多物理量分布的一维模拟

One-dimensional simulation on the distribution of physical variables in DMFC

为了研究直接甲醇燃料电池(DMFC)内的电流、电位和各物质的浓度等物理变量的分布,建立了沿电池厚度方向的一维模型。模型的研究区域包括阳极扩散层、阳极催化层、质子交换膜、阴极催化层和阴极扩散层。模型中较细致地描述了甲醇氧化的多步骤复杂反应,而催化层结构采用团聚体模型来描述,模型中还考虑了甲醇穿透对阴极氧气反应的影响和甲醇进料浓度对各物理量分布的影响。从模拟结果可以看到,在阳极扩散层由于甲醇氧化反应速率较大,甲醇在阳极催化层两侧的浓度梯度大于阳极扩散层浓度梯度;由于扩散层厚度远远大于催化层厚度,甲醇在阳极扩散层的浓度差比在阳极催化层的浓度差大;在阴极催化层由于甲醇氧化反应速率较小,甲醇浓度变化很小;电池内膜相电位不同导致各处过电位不同。

In order to investigate the distribution of concentration, current density and overpotential in DMFC, a one-dimensional mathematic model including anode diffusion layer, anode catalyst layer, polymer electrolyte membrane, cathode catalyst layer and cathode diffusion layer is established. In this model, kinetic equations of methanol oxidation are deduced based on the multi-step reaction mechanism. An agglomerate model of catalyst layer is used to describe diffusion limitations in a microscopic level. The influence of methanol on the reaction of oxygen is also considered in cathode catalyst layer. Simulation results show that the concentration gradient of methanol in anode catalyst layer is greater than all the other layers; the concentration gradient of methanol in cathode catalyst layer is small.