用球磨法制备的主客体Fe-TPP⊂ZIF前驱体制备用于ORR和锌空电池的Fe单原子催化剂 (Well-elaborated, mechanochemically synthesized Fe-TPP⊂ZIF precursors (Fe-TPP = tetraphenylporphine iron) to atomically dispersed iron–nitrogen species for oxygen reduction reaction and Zn-air batteries) - 主-客体和超分子化学

在这篇论文中，我们使用主客体型Fe-TPP⊂ZIF复合化合物作为前驱体热解得到了Fe单原子级分散的铁氮掺杂的多孔碳材料，并作为电催化剂用于氧还原反应和锌空电池。论文主要要点有： 1.主客体型Fe-TPP⊂ZIF为首次报道，其中ZIF基质为较难制备的rho型ZIF（该类ZIF内腔直径约为22埃，可以容纳Fe四苯基卟啉客体分子，远大于常见的内径约12埃的sod型ZIF-8），卟啉客体以分子级别分散在ZIF内腔中。 2.前驱体制备过程使用原位机械球磨法，Fe单原子材料使用高温热解，因此整个制备为两步非溶液过程，具有简易绿色高效的优势。 3.Fe单原子状态通过球差电镜和X射线精细吸收谱表征，并模拟其配位环境为Fe-N4，表征较为全面。 4.ORR测试碱性条件下半波电位约0.895 V，优于Pt-C，经10000次循环无明显衰减。 Although atomically dispersed Fe-N species as electrocatalysts often exhibit high activity for oxygen reduction reaction (ORR), the rational design and facile fabrication of single-atom Fe-N species-based catalysts remains a great challenge because of their easy aggregation. Herein, a new precursor of host-guest Fe-TPPrho-ZIF (Fe-TPP = tetraphenylporphyrin iron; rho-ZIF = zeolitic imidazolate framework with the rho topology) for the first time was elaborately designed and readily prepared by one-pot mechanochemical method, and then was pyrolyzed into Fe-N/C catalysts with no need of solution-based steps and post-ammonia/acid treatments, which greatly simplified the preparation procedures. Owing to the host-guest confinement at the molecular level, the encapsulated Fe centers within interior cavities of rho-ZIF host matrice can be effectively isolated during pyrolysis to afford atomically dispersed Fe-N4 moieties anchored on the carbon matrice. Such a well-elaborated precursor not only endows the final product with the single-atom characteristic, but also with high Fe loading (up to 3.8 wt%) and specific surface area. Benefitting from the outstanding compositional and structural advantages, the resultant Fe-N/C exhibits highly efficient ORR activity with E1/2 of 0.895 V in 0.1 M KOH, ~50 mV more positive than that of the commercial Pt/C, which is among the top-level ORR electrocatalysts to date. It has excellent stability and displays a negligible change after a 10000-cycle accelerated durability test. Moreover, rechargeable Zn-air batteries were also assembled to demonstrate the practical application of the as-obtained Fe-N/C as air cathode catalyst. Our work may provide an insight into the facile and large-scale production of high-performance and durable non-precious metal catalysts with atomic-level dispersion.