质子交换膜电解槽钛毡扩散层表面微孔层结构对电解水特性的影响

Effect of Microporous Layer on Water Electrolysis for Proton Exchange Membrane Electrolyzers

摘要:

为研究微孔结构扩散层对钛毡表面接触及传输的影响，分别在0.25、0.4和0.6 mm厚的钛毡表层通过钛粉填充再真空烧结方法制备了微孔结构扩散层。采用激光共聚焦显微镜、压汞仪、电解池在线测试等分析表征了表面接触面积及电阻、孔径分布、伏安曲线等特性。结果表明，0.25、0.4和0.6 mm厚微孔钛毡扩散层的有效接触面积相较原始钛毡的3.1%分别提高到11.2%、22.8%、4.8%，在1.5 MPa接触压力下的接触电阻分别降低至7.07、5.26、7.86 mΩ·cm²，微孔层通过优化表面孔隙结构进而降低接触电阻；扩散层孔径分布特征由双峰结构演变为三峰结构，新增的6~32 μm小孔通道有利于水传输，中孔及大孔通道有利于氧气泡传输；在2 A/cm²电流密度下，0.4 mm厚微孔扩散层过电位降幅最大为45 mV，同时接触电阻最低、孔径分布均衡、电解水效率最高。

Abstract:

To study the influence of microporous layer (MPL) on the surface contact and transmission characteristics of titanium felt porous transport layer (PTL), the MPL was prepared by vacuum sintering after the surface of titanium felts with 0.25 mm, 0.4 mm and 0.6 mm in thickness were filled with titanium powder. The surface contact area/resistance, pore size distribution and polarization curve of electrolytic water measured by laser scanning confocal microscope, mercury porosimetry and electrolysis cell, respectively. The results show that the effective contact area of the PTLs with MPL increase from 3.1% to 11.2%, 22.8% and 4.8% compared with that of titanium fiber felt. In addition, the contact resistances decrease to 7.07, 5.26 and 7.86 mΩ·cm² at the contact pressure of 1.5 MPa. The pore size distribution changes from the bimodal structure of PTL to the trimodal structure of PTL with MPL. The addition of a small pore size channel of 6–32 μm is conducive to liquid water transmissions; meanwhile, medium & large pore size channels are beneficial to gas phase transmission. The overpotential of the different thickness PTLs with MPL decrease by 12 mV, 45 mV and 32 mV at current density of 2 A/cm². In this case, the contact resistance is the lowest, the pore size distribution is uniform, and the electrolysis efficiency of porous transport layer with 0.4 mm in thickness is the highest.