抗团聚高分散超低铂-非金属复合催化剂的构筑与催化特性研究

Developing catalysts with low cost and high performance for oxygen reduction reaction (ORR) has been one of the major challenges for large-scale application of fuel cells. Based on the poor ORR activity of the existing non-precious metal catalysts, we present a high dispersion of ultra-low Pt loading metal-free composite catalyst to address, for the first time, both the activity and durability issues of partial substitution of precious metals catalyst. In this method, a layer of polyaniline or polypyrrole with graphite structure and easy-graphitization was firstly coated on the carbon surface of Pt-M/C catalyst (M = Fe, Co., Ni, Ir, and Ti) by in-situ chemical oxidation polymerization method, and then the Pt@M shell/core nanoparticles and nitrogen-doped graphene catalyst layer were one-step synthesized under heat treatment conditions by using the surface segregation between Pt and transition metal (M=Fe、Co、Ni、Ir、Ti) and the induced effect of transition metal salt (Fe、Co、Ni) to nitrogen-doped graphene. The CN@Pt@M/C composite catalysts prepared by this method, which not only can retain the advantages of shell/core catalyst, but also can significantly improve the catalytic activity due to the synergistic catalytic effect between Pt and nitrogen-doped graphene. Moreover, the stability of Pt@M nanoparticles can be enhanced by nitrogen-doped graphene, which can help to inhibit Pt dissolution, ripening and aggregation due to the confinement effect of CN nitrogen-doped graphene to Pt@M nanoparticles, and provide corrosion resistance to the carbon support. The synthetic methods and catalytic mechanism of CN@Pt@M/C catalyst was explored through the regulation of the thickness of polyaniline or polypyrrole and pyrolysis conditions, combining with the density functional theory (DFT) and molecular dynamics (MD) method to the level of atoms and molecules.

发展低成本、高性能的氧还原催化剂是实现燃料电池商业化的关键。针对现有非贵金属催化剂存在的活性的问题，本申请提出贵金属部分替代的"高分散超低Pt-非金属复合催化剂"。拟采用原位化学氧化聚合的方法将具有类石墨结构、易于石墨化的聚苯胺或聚吡咯包覆在Pt-M/C表面（M=Fe、Co、Ni、Ir、Ti等），高温热解借助Pt-M中Pt偏析效应一步合成Pt@M "壳/核"纳米粒子与氮掺杂类石墨烯层。这种复合催化剂不仅具有核壳结构催化剂的优势，而且氮掺杂类石墨烯层还会协同加强Pt催化ORR的活性。此外，氮掺杂类石墨烯纳米壳层的限域作用还可以抑制Pt@M纳米粒子在碳表面的迁移、团聚长大，提高催化剂的稳定性。通过对聚合物修饰层厚度以及热解条件的调控，结合密度泛函（DFT）与分子动力学（MD）方法，探索高效高稳定性超低Pt-非金属

发展低成本、高性能的氧还原催化剂是实现燃料电池商业化的关键。针对传统Pt基催化剂存在的活性低与稳定性差问题，本项目提出高分散超低Pt-非金属复合催化剂构筑方案，在项目执行过程中发表论文20篇，其中SCI论文16篇，申请发明专利7项，获授权发明专利4项，培养研究生8名。取得的创新性成果有：（1）发明了基于“空间限域”和“柯肯达尔效应”的催化剂结构演变方法，实现了从实心Pt纳米粒子到Pt表面富集中空PtFe合金纳米粒子的结构转化。合成的中空PtFe合金催化剂在0.9V下的质量活性达到0.993A/mgPt，较商业化Pt/C催化剂提升了5.15倍，是美国DOE2017年度目标0.44A/mgPt的2.26倍。该研究成果发表在国际顶级期刊先进材料（Advanced Materials, 2016, 28, 10673-10678）上，国内知名资讯平台X-MOL对文章进行了重点报道；（2）首次通过原位化学氧化聚合、高温碳化的方法构建了一个高效稳定的低Pt复合催化剂；（3）以三重金属碳化物钛铝碳（Ti3AlC2）为原材料，通过化学刻蚀的方法，制备了一种具有优异电化学稳定性的碳基替代载体材料；（4）发展建立了燃料电池催化剂稳定性快速评价方法。