高温质子交换膜燃料电池铂催化剂耐久性能研究

High-temperature proton exchange fuel cells (HT-PEMFC) operated at 100-200℃ are considered as the next generation of fuel cell technology for improved power density, enhanced reliability and reduced cost. However, current Pt catalysts are commonly supported on amorphous carbon. During utilization, the amorphous carbon could be corroded, and the Pt particles could migrate and aggregate. Such degradation becomes severer at temperatures above 100℃. The present research proposal concerns a systematic study of the HT durability and development of a new catalyst based on carbon nanocages (CNC) for HT-PEMFC. Specifically, the growth mechanism of CNC and the effects of preparation technique and doping modification are studied, and new methods are searched to increase the surface area, degree of graphitization and the number of active sites. Furthermore, the catalyzing mechanism and the migration/aggregation behavior of the Pt particles on CNC are investigated. In order to improve the stability of the catalyst, alloying and surface modification approaches are examined. At last, the catalytic activity, stability and evolution of the new catalyst under the conditions of high temperatures and high contents of CO in H2 fuel are evaluated with a close collaboration with a potential user. The present research is of significant importance to the development of catalysts with high catalytic activity and long term durability as well as the practical applications of HT-PEMFC.

高温质子交换膜燃料电池(HT-PEMFC)是燃料电池的发展新方向,这是因为将工作温度提高到100-200℃,能明显提高功率密度,改善可靠性和降到成本。但目前在PEMFC中普遍采用以非晶碳为载体的铂系催化剂。在使用过程中,这样的载体会被氧化腐蚀,Pt粒子会团聚和失稳。在100℃以上，催化剂的稳定性会变得更差。本课题拟系统研究催化剂的高温耐久性能,研发所急需的新型催化剂。具体是研究碳纳米笼(CNC)的生长机理，制备工艺和掺杂改性,探索提高CNC的表面积,石墨化程度和活性点位的新方法;进一步研究Pt纳米粒子在CNC上的催化机理,迁移和团聚特征,合金化和表面改性的作用,寻找提高其稳定性的技术途径;与应用单位密切合作,研究新型催化剂的电催化活性和稳定性,揭示其在高温和使用高CO含量的燃料情况下的演变规律。本研究对开发高活性、高耐久性电催化剂，促进HT-PEMFC实际应用具有十分重要意义。

高温质子交换膜燃料电池(HT-PEMFC)是燃料电池的发展新方向，这是因为将工作温度提高到100-200℃，能明显提高功率密度，改善可靠性和降到成本。但目前在PEMFC中普遍采用以非晶碳为载体的铂系催化剂。在使用过程中，这样的载体会被氧化腐蚀，Pt粒子会团聚和失稳。在100℃以上，催化剂的稳定性会变得更差。本项目系统研究了催化剂的高温耐久性能，研发了所急需的新型催化剂。具体是研究了碳纳米笼(CNC)的生长机理，制备了具有完好石墨结构，高比表面积(400-800 平方米/克)的碳纳米笼(CNC)载体。进一步通过N掺杂，实现了细小Pt纳米粒子(~3nm)在CNC表面的均匀沉积，使Pt/CNC催化活性比以传统碳黒为载体的商用JM催化剂（Pt/C）提高30%以上。基于N掺杂的CNC载体，研制了PtIr 合金催化剂，大大提高了在酸性介质中的抵抗电化学腐蚀和在200℃高温下的抵抗空气氧化的性能，有望应用于HT-PEMFC。通过化学组成和后续热处理的控制，研制了PtFe系列金属间化合物催化剂，使其兼顾高活性，高耐久性和低Pt用量的优点。本研究对开发高活性、高耐久性电催化剂，促进PEMFC实际应用具有十分重要意义。