高温应用“储水囊”改性Nafion膜开发及匹配低铂甲醇氧化催化剂研制

Aimed to the issues of methanol crossover and noble-metal dependence in the direct methanol fuel cells (DMFCs), “water reservoir” non-destructively modified Nafion membrane and low-platinum transition metal carbide (TMC) based methanol oxidation catalyst with matched operation temperature will be designed to elevate the operation temperature of DMFC to 100-120 ºC. The two issues can therefore be resolved together with the double-phase fluid issue, which would strongly influence the performance and life of the DMFC stack. By combining the morphology characterization on nano “water reservoir” and key performance measurement on modified Nafion membrane, highly selective proton condition under high temperature and low humidity can be achieved through the optimization on morphology of the nano “water reservoir” and its synergistic strategy with the proton conductive channel in Nafion. At the same time, with the assistance of theoretical modeling, matching-up mechanism of water dissociation reaction on TMC and methanol dissociation reaction on Pt would be studied to guide the development of low-Pt high temperature methanol oxidation Pt/TMC catalysts. With the optimized modified Nafion membrane and Pt/TMC catalyst with matched operation temperature, multi-scale porous structure of electrode was optimized and cost-effective DMFC would be assembled with the help of computational fluid dynamics simulation for long-term operation. Finally, low-power high temperature DMFC stack would be developed for practical power supply.

本项目针对直接甲醇燃料电池(DMFC)存在的燃料渗透及贵金属依赖问题，通过研制运行温度匹配的“储水囊”无损改性Nafion膜及过渡金属碳化物(TMC)基低铂甲醇氧化催化剂以提升DMFC运行温度至100-120ºC，从器件设计角度出发缓解这两个问题的同时，解决严重影响DMFC电堆性能及寿命的两相流问题。结合“储水囊”纳米形貌表征及质子交换膜关键性能测试，通过对“储水囊”纳米结构及其与Nafion膜质子传输通道协同方式的优化，实现改性Nafion膜在高温低湿条件下高效选择性传输质子；基于TMC高效催化水解离的特性，结合理论计算，探寻Pt/TMC催化甲醇双功能氧化过程的温度依赖机制并合成低Pt载量Pt/TMC催化剂；基于温度匹配的改性Nafion膜及Pt/TMC催化剂，结合流体动力学模拟，优化电极多尺度孔结构、组装廉价DMFC并进行高温长效稳定运行，进而试制小型高温DMFC电堆进行长效供电测试。

本项目根据研究计划，首先通过控制有机或无机类“储水囊”合成细节调控“储水囊”尺寸、纳米形貌等因素，同时通过控制“储水囊”改性过程，实现“储水囊”改性质子交换膜高温性能的提升；使用Nafion膜中质子传输通道（PCC）作为纳米反应器原位制备SiO2纳米“储水囊”实现其与Nafion膜原有PCC的高效协同，进一步提升Nafion膜的高温质子传输性能；研究“储水囊”改性Nafion膜的高温低湿质子电导率、热稳定性、机械性能等重要物理化学参数并优化得到数种基于 Nafion 的改性质子交换膜；结合电子显微技术、小角X射线散射等表征技术对“储水囊”改性Nafion膜的高温质子传输通道微观结构进行表征，总结得到“储水囊”Nafion膜构效关系；以Mo2C为基底，开发不同高效Pt负载制备方法，研制得到数种高效低Pt/Mo2C催化剂，并探讨其促进MOR催化活性机制；同时考虑到Mo2C催化水解离反应的高活性，还探讨了低Pt/非Pt Mo2C基催化剂在电解水制氢领域的应用。结合膜电极组件制备方案的优化，项目实现了基于Nafion改性膜的燃料电池在100-120 ºC温度下的高效运行。总得来说，本项目针对DMFC为代表的低温质子交换膜燃料电池存在的关键材料问题，分别从质子交换膜和催化剂角度开展了相关研究，实现了两类材料性能的突破已经成本的下降，能够推动廉价高效燃料电池及电解水技术的推广应用。