Zhu Ruijie, Zhan Zhigang, Zhang Heng, Du Qing, Chen Xiaosong, Xiang Xin, Wen Xiaofei, Pan Mu
State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China.
Donghai Laboratory, Zhoushan 316022, China.
Polymers (Basel). 2023 Mar 24;15(7):1629. doi: 10.3390/polym15071629.
The gas diffusion layer (GDL) is an important component of proton exchange membrane fuel cells (PEMFCs), and its porosity distribution has considerable effects on the transport properties and durability of PEMFCs. A 3-D two-phase flow computation fluid dynamics model was developed in this study, to numerically investigate the effects of three different porosity distributions in a cathode GDL: gradient-increasing (Case 1), gradient-decreasing (Case 3), and uniform constant (Case 2), on the gas-liquid transport and performance of PEMFCs; the novelty lies in the porosity gradient being along the channel direction, and the physical properties of the GDL related to porosity were modified accordingly. The results showed that at a high current density (2400 mA·cm), the GDL of Case 1 had a gas velocity of up to 0.5 cm·s along the channel direction. The liquid water in the membrane electrode assembly could be easily removed because of the larger gas velocity and capillary pressure, resulting in a higher oxygen concentration in the GDL and the catalyst layer. Therefore, the cell performance increased. The voltage in Case 1 increased by 8% and 71% compared to Cases 2 and 3, respectively. In addition, this could ameliorate the distribution uniformity of the dissolved water and the current density in the membrane along the channel direction, which was beneficial for the durability of the PEMFC. The distribution of the GDL porosity at lower current densities had a less significant effect on the cell performance. The findings of this study may provide significant guidance for the design and optimization of the GDL in PEMFCs.
气体扩散层（GDL）是质子交换膜燃料电池（PEMFC）的重要组成部分，其孔隙率分布对PEMFC的传输特性和耐久性有相当大的影响。本研究建立了一个三维两相流计算流体动力学模型，以数值研究阴极GDL中三种不同孔隙率分布（梯度增加（案例1）、梯度减小（案例3）和均匀恒定（案例2））对PEMFC气液传输和性能的影响；其新颖之处在于孔隙率梯度沿通道方向，并且相应地修改了与孔隙率相关的GDL物理性质。结果表明，在高电流密度（2400 mA·cm）下，案例1的GDL沿通道方向的气体速度高达0.5 cm·s。由于气体速度和毛细压力较大，膜电极组件中的液态水可以很容易地去除，从而导致GDL和催化剂层中的氧浓度较高。因此，电池性能提高。与案例2和案例3相比，案例1的电压分别提高了8%和71%。此外，这可以改善膜中溶解水和电流密度沿通道方向的分布均匀性，这有利于PEMFC的耐久性。在较低电流密度下，GDL孔隙率分布对电池性能的影响较小。本研究结果可为PEMFC中GDL的设计和优化提供重要指导。
