质子交换膜燃料电池阴极数学模型

Cathode mathematical model of proton exchange membrane fuel cell

Ｓｔｅｆａｎ－Ｍａｘｗｅｌｌ方程用于氧在扩散层内传递；稳态连续方程和Ｆｉｃｋ 第一定律分别用于氧在催化层内气体通道和电解质膜中传递，采用一维宏观均匀模型，建立了质子交换膜燃料电池氧电极的数学模型。给出了反应速度和氧气浓度在催化层内分布，并分析了各种参数对氧电极性能的影响。结果表明：（１）当催化层内气相孔隙率为０．０１以上，则氧在催化层内浓度分布就趋于均匀；（２）催化层厚度为２５ μｍ 左右最佳，过厚影响传质，过薄不能提供足够的反应界面；（３）提高催化层内质子电导和催化剂的有效表面积将极大地提高电极性能；（４）低电流密度时，反应在催化层内分布均匀；高电流密度时，反应集中在催化层靠近扩散层一则。

The mathematical model of oxygen electrode in proton exchange membrane fuel cell (PEMFC) was established by adopting the macroscopic homogeneous model in one dimension. In the mathematical model,Stefan Maxwell Equation was used for oxygen transferring in diffusion layer as well as Steady Continuous Equation and Fick First Law was used for oxygen transferring in catalyst layer gas channel and in membrane respectively. The distributions of reaction rate and oxygen concentration in catalyst layer were given and the effects of various parameters on the performance of oxygen electrode were analyzed. The results show that: (1) If the porosity of gas phase in catalyst layer is over 0.01, the distribution of oxygen concentration in catalyst layer trends to homogeneity; (2) The best thickness of catalyst layer is about 25 μm; (3) The performance of electrode will be improved by means of the improvement of the proton conductivity in catalyst layer and the effective area of catalyst; (4) For low current density, the distribution of reaction rate is nearly homogeneous while most of the reactions occurred near the diffusion layer in catalyst layer for high current density.