质子交换膜燃料电池金属阴极板表面改性层微孔腐蚀及其自愈合机理研究

The fuel cell with metal bipolar plate is considered to be the best candidate for vehicle application for its high power density.In our preliminary study, 316L stainless steel sheet was coated with carbon based chromium doped nanometer composite film by arc ion plating technology, and the bipolar plate material showed good corrosion resistance and electrical conductivity in fuel cell operation. The cost of bipolar plate was also greatly reduced. However, the pin-hole corrosion shortened the stack life. As we know, corrosion medium and potential difference are the two necessary conditions for electrochemical corrosion. In our study, we take advantage of the potential drift of the pin-hole area when corrosion occurred to prevent further corrosion if the potential of the corrosion product was lower than that of the main surface coating. Specifically, a transition layer will be prepared between the 316L stainless steel sheet and the carbon based surface film, and material and thickness of the transition layer should be scientific designed to control corrosion potential trend and meet the target. Thus the metal bipolar plate with self-cured function is obtained.

采用全金属结构双极板可以大幅度提高质子交换膜燃料电池的比功率密度，是车用燃料电池的必然选择。在前期研究中，采用电弧离子镀技术在316L不锈钢薄板上镀制碳基铬掺杂纳米复合改性层所获得的双极板材料在实际电池运行过程中显示出很好的耐蚀、导电性能，成本也得到大幅降低，但改性层微孔腐蚀影响了电池寿命。本项目从电化学腐蚀发生的两个必要条件之一的腐蚀电势出发（另一个为腐蚀介质），利用微孔处发生腐蚀时腐蚀产物使局部微区电位漂移的原理，通过科学设计微区材料和物质量来控制腐蚀电位的变化趋向，从而降低微孔处腐蚀电位并使之低于主改性层材料，以最终解决阴极板的微孔腐蚀问题。

随着环境和能源问题的不断加重，车用燃料电池商业化进程得到快速推进，目前丰田Mirai和现代ix35已经开始小批量销售，而本田、戴姆勒、奥迪、通用等车企也有明确的燃料电池量产计划。金属板有助于大幅提高电堆比功率密度、大幅降低成本，是车用燃料电池的必然选择。而碳基涂层兼具耐蚀、导电的优点，同时材料易于获取且成本低廉，是理想的金属板表面改性材料。本项目针对金属板阴极改性层的腐蚀机理及高性能改性层开发展开研究，同时考虑了量产可行性，对推进我国车用燃料电池产业化进程意义重大。通过过渡层金属元素的优选、过渡层的氧化处理以及过渡层氧化处理在镀膜工艺上的实现研究，获得了兼具耐蚀、导电优良性能的长寿命改性层；采用1.5Pa氧离子处理0.5h制备Cr过渡层进而镀Cr/C，在1.2MPa下的电阻<5mΩ•cm2，在0.5M H2SO4+5ppmF-模拟燃料电池动电位和恒电位腐蚀条件下的腐蚀电流都达到了10-7A•cm-2的项目指标；在实际车载工况条件下的运行寿命预计超过5000h。