含氮碳纳米团簇对Pt基纳米金属粒子的锚定效应及电催化性能影响

Proton exchange membrane fuel cells (PEMFCs) have attracted much attention as promising power sources due to their environmentally friendly,high power density, and low operating temperatures. However, a big challenge in the commercialization of PEMFCs is the low stability of catalysts during extended operation and repeated cycling of fuel cells.Presently,the stability of PEMFC catalysts have been improved in some extend by altering the crystal face indexes or morphology of active metals (i.e.,Pt), modifying the active metals with polymer stabiliation or selecting the highly chemical and electrochemical stable supports. However, there is a great disparity between the improvement and the 5000h lifespan standard under real PEMFC operation made by American DOE (Department of Energy).In this work, on the basis of our previous studies, we propose a novel strategy to greatly enhance the catalyst lifespan through the strong anchoring effect of nitrogen-containing carbon nanoclusters to active metals on alternatively stable supports(i.e., graphitic nanocarbon and conductive nanoceramics). Also, the nitrogen-containing carbon nanoclusters encapsulated catalysts origined from the carbonization of nitrogen-containing polymers (i.e., polyaniline) could improve the catalytic activity due to the increased active sites of catalysts.The carbonization reaction would be controlled to tune the structure of nitrogen-containing carbon nanoclusters and catalysts, and then the anchoring effect of nitrogen-containing carbon nanoclusters on active metals, and the catalytic activity, stability and CO endurance of our new as-prepared catalysts, with low or ultralow Pt loading, are studied in detail.

质子交换膜燃料电池（PEMFC）催化剂的稳定性问题是阻碍PEMFC产业化的重要瓶径之一。当前，通过改变活性金属（如Pt）的晶面指数或晶形、金属表面聚合物稳定化或采用更稳定的催化剂担体等方法，催化剂的稳定性得到一定改善，但与PEMFC长期工作5000h的美国能源部国际标准相比还有较大差距。为此，在前期研究基础上，申请人提出了一种通过含氮碳纳米团簇的锚定效应，大幅改善催化剂稳定性的研究思路：即首先对活性金属表面进行含氮聚合物稳定化并担载，然后将聚合物炭化生成含氮碳纳米团簇。形成的碳纳米团簇可将金属纳米粒子牢固地锚定在优选的抗氧化担体表面，增大金属-担体作用力，大幅改善催化剂稳定性；而且，氮碳纳米团簇中的结构氮还可增加催化剂的活性位，有助于提高催化剂的电催化活性。本项目重点研究含氮碳纳米团簇的合成路径、结构调控及锚定效应，并对合成的低或超低Pt催化剂的催化活性、稳定性及CO耐受性进行系统研究。

Pt基催化剂通常具有较差的稳定性，主要归因于碳载体的热力学和电化学稳定性差。随着工作电压的提高，碳载体将会发生严重的电化学腐蚀，导致Pt基催化剂发生迁移、团聚及脱落，使催化剂发生降解。Pt基催化剂的稳定性问题严重阻碍了质子交换膜燃料电池（PEMFC）燃料电池产业化的发展及在氧析出反应（OER）中的应用。针对该重要的科学问题，申请人提出了一种通过含氮碳纳米团簇的锚定效应大幅改善催化剂稳定性的研究思路：首先对活性金属表面进行含氮聚合物稳定化并担载，然后将聚合物炭化生成含氮碳纳米团簇。形成的碳纳米团簇可将金属纳米粒子牢固地锚定在优选的抗氧化担体表面，增大金属-担体作用力，大幅改善催化剂稳定性；而且，氮碳纳米团簇中的结构氮还可增加催化剂的活性位，有助于提高催化剂的电催化活性。经过三年的努力研究，按照原计划已制备出了具有高催化活性、低Pt 和长寿命特性的质子交换膜燃料电池催化剂，并获得了对Pt基金属表面碳纳米团簇和含氮碳纳米团簇的结构和锚定效应的新认识。作为一作或通讯作者，项目完成人已在Advance Materials、Angewandte Chemie International Edition、Advanced Functional Materials、Nano Energy、ACS Energy Letters等期刊上已发表SCI收录论文55篇，申请国家发明专利11件，已培养研究生17 名（已毕业），其中硕士12名、博士5名，均已完成研究目标。