Liu Yang, Diankai Qiu, Xu Zhutian, Yi Peiyun, Peng Linfa
State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, Shanghai 200240, P. R. China.
Shanghai Key Laboratory of Digital Manufacture for Thin-walled Structures, Shanghai Jiao Tong University, Shanghai 200240, P. R. China.
ACS Appl Mater Interfaces. 2024 Sep 11;16(36):47357-47367. doi: 10.1021/acsami.4c00006. Epub 2024 Aug 30.
A reasonable porous transport layer (PTL) is crucial to decreasing the mass-transfer loss in proton-exchange membrane water electrolyzers (PEMWEs). In this study, it was experimentally demonstrated that the gradient porosity PTL is beneficial in improving the performance of electrolyzers. The research comprehensively investigates the impact of gradient porosity PTL structures on the performance of the PEMWE, considering mass transfer and interfacial contact. It offers insights into the two-phase (oxygen-water) flow transport mechanisms within the PTLs using a 2D numerical model based on the actual PTL geometry. At the microscopic level, it analyzes how the interfacial contact impacts proton and electron transport mechanisms, affecting not only the contact resistance but also the number of effective catalytic sites for the oxygen evolution reaction. Experimental results demonstrate that the cis-gradient porosity PTL leads to a performance enhancement of 9.3% at 2.2 A/cm. Numerical simulations reveal that the drivers of oxygen transport include the surface tension of the fibers and the pressure drop influenced by the local PTL porosity. Further analysis indicates that the lower oxygen saturation in the bottom region of the PTL with cis-gradient porosity favors a lower oxygen coverage area in the catalyst layers (CL) since the narrower pore space and higher capillary pressure increase the number of water flow paths into the CL. Overall, this study provides valuable insights for designing high-performance PTLs for use in electrolyzers.
合理的多孔传输层（PTL）对于降低质子交换膜水电解槽（PEMWE）中的传质损失至关重要。在本研究中，通过实验证明了梯度孔隙率PTL有利于提高电解槽的性能。该研究综合考察了梯度孔隙率PTL结构对PEMWE性能的影响，同时考虑了传质和界面接触。利用基于实际PTL几何形状的二维数值模型，深入研究了PTL内的两相（氧气-水）流动传输机制。在微观层面，分析了界面接触如何影响质子和电子传输机制，这不仅影响接触电阻，还影响析氧反应的有效催化位点数量。实验结果表明，顺梯度孔隙率PTL在2.2 A/cm²时可使性能提高9.3%。数值模拟表明，氧气传输的驱动因素包括纤维的表面张力和局部PTL孔隙率影响的压降。进一步分析表明，具有顺梯度孔隙率的PTL底部区域较低的氧气饱和度有利于催化剂层（CL）中较低的氧气覆盖面积，因为较窄的孔隙空间和较高的毛细管压力增加了进入CL的水流路径数量。总体而言，本研究为设计用于电解槽的高性能PTL提供了有价值的见解。
