Abstract:

Due to the planar surface structure inherent in commercial Nafion membranes, the interface contact area between the membrane and catalyst layer is limited, resulting in a mere 25%—35% utilization rate of Pt-based catalysts in PEMFCs. To enhance the utilization efficiency of Pt-based catalysts, the inspiration from the naturally occurring hierarchical structures found on lotus leaves was drawn. In this study, these microstructures as templates to create patterned microwire arrays were employed. The surface microstructure of lotus leaves was first meticulously by using a PDMS casting agent replicatedby. Subsequently, this distinctive textured surface of lotus leaves was accurately transferred onto the Nafion membranes. This process yielded patterned microwire arrays with average diameters of (5.89±1.45)μm and (6.95±1.70)μm, respectively. Through meticulous optimization, the performance of the membrane electrode assembly (MEA) was significantly improved. Notably, the maximum power density increased from 0.625W/cm² to 0.757W/cm². These patterned microwire arrays augmented the surface hydrophobicity of the Nafion membrane, thereby enhancing mass transfer efficiency and reducing the reaction/internal resistance within the MEA. To probe the impact of these patterned microwire arrays on Pt catalyst utilization, the cyclic voltammetry was employed. This analysis revealed a 151% increased in the electrochemical surface area (ECSA) and a 43.4% of Pt utilization rate. In summary, the fabrication of patterned microwire arrays on Nafion membrane surfaces facilitated the formation of a three-phase interface for electrons, protons and reactants, improving the interface structure between the Nafion membrane and catalytic layer, and ultimately leading to a marked improvement in Pt utilization rate.

Key words: Nafion membrane, microwire array, mass transfer enhancement, fuel cell

摘要：

质子交换膜燃料电池（PEMFCs）中商业Nafion膜的平整表面结构造成膜和催化层界面接触面积偏小，Pt基催化剂利用率低，仅有25%~35%。为了提高催化层中Pt利用率，本工作以荷叶表面自然生长的乳突结构为模板，采用PDMS铸模剂复刻荷叶表面微观结构，再将图案化纹理结构精确转印到Nafion膜表面，分别构筑了平均直径为(5.89±1.45)μm和(6.95±1.70)μm的微米线阵列结构。用图案化Nafion膜组装的单电池性能显著提升，最大功率密度由0.625W/cm²提升至0.757W/cm²。通过构建图案化结构能增强Nafion膜表面疏水性，强化传质效率，降低膜电极反应电阻和内阻。通过循环伏安曲线考察了Nafion膜上微米线阵列结构对Pt催化剂利用率的影响，Pt基催化剂的电化学活性面积（ECSA）结果提高了151%，Pt利用率提高至43.4%。在Nafion膜表面构筑微米线阵列有利于形成电子/质子/反应物的三相反应界面，改善质子交换膜与催化层间界面结构，显著提升了Pt利用率。

关键词: Nafion膜, 微米线阵列, 传质强化, 燃料电池