气体扩散层(gas diffusion layer, GDL)是质子交换膜燃料电池(polymer electrolyte membrane fuel cell, PEMFC)的关键部件之一。使用导电纳米碳黑、多壁碳纳米管(multi-walled carbon nanotubes, MWCNTs)和石墨片为微孔层碳材料,采用分层涂覆的方法,在碳纸基底层上构建具有梯度孔结构的微孔层。采用扫描电镜与压汞仪分析各扩散层的微观形貌及孔隙结构,测定扩散层的电阻率、透气率和突破压力,采用燃料电池测试平台测定单电池的输出性能。结果表明,MWCNTs层和石墨片层孔径呈“双峰”分布,形成了梯度孔结构微孔层,可促进气液两相传输的分离,从而提升电池的传质能力。与双层设计相比,具有三层梯度孔径结构微孔层的扩散层性能更优异,电流密度达5.5 A/cm2时仍未出现明显传质极化,最大功率密度为1 855 mW/cm2,相比于商品气体扩散层提高21%。
As one of the key components of PEMFC (polymer electrolyte membrane fuel cell), the GDL (gas diffusion layer) plays a crucial role in the water management of the battery, The microporous layers with different gradient pore structures were constructed on the carbon paper substrate using conductive nano carbon black, MWCNTs and graphite sheets as microporous carbon materials. Scanning electron microscope and mercury injection instrument were used to measure the micropore morphology and pore structure of the all microporous layers. Then the resistivity, gas permeability and breakthrough pressure of the diffusion layers were also tested. Finally, the output performance of a single cell was studied by a fuel cell test platform. The results show that the gradient pore structure porous layer is formed due to the “double peak” distribution of MWCNTs layer and graphite sheet layer, which promotes the separation of gas-liquid two-phase transport and improves the battery's mass transfer capacity. Compared with the double-layer design, the three-layer gradient pore structure microporous layer has better performance. When the current density reaches 5.5 A/cm2, there is no obvious mass transfer polarization of the diffusion layer, and its maximum power is 1 855 mW/cm2. Compared with the commercial GDL, it is increased by 21%.
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