Choi Hyun Chul, Park Jeunghee, Kim Bongsoo
Department of Chemistry, Korea University, Jochiwon 339-700, Korea.
J Phys Chem B. 2005 Mar 17;109(10):4333-40. doi: 10.1021/jp0453109.
We investigated the inhomogeneous distribution of concentration and electronic structure of the nitrogen (N) atoms doped in the multiwalled carbon nanotubes (CNTs) by variable-energy X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge structure, and electron energy-loss spectroscopy. The vertically aligned N-doped CNTs on the substrates were grown via pyrolysis of iron phthalocyanine (FePc), cobalt phthalocyanine (CoPc), and nickel phthalocyanine (NiPc) in the temperature range 750-1000 degrees C. They usually have a bamboo-like structure, and the diameter is in the range of 15-80 nm. As the photon energy of XPS increases from 475 to 1265 eV, the N content increases up to 8 atomic %, indicating a higher N concentration at the inside of nanotubes. We identified three typed N structures: graphite-like, pyridine-like, and molecular N(2). The pyridine-like N structure becomes significant at the inner walls. Molecular N(2) would exist as intercalated forms in the vicinity of hollow inside. The XPS valence band analysis reveals that the pyridine-like N structure induces the metallic behaviors. The CNTs grown using NiPc contain the higher content of pyridine-like structure compared to those grown using FePc and CoPc, so they exhibit more metallic properties.
我们通过可变能量X射线光电子能谱（XPS）、X射线吸收近边结构和电子能量损失谱，研究了多壁碳纳米管（CNT）中掺杂氮（N）原子的浓度和电子结构的不均匀分布。通过在750 - 1000摄氏度的温度范围内热解铁酞菁（FePc）、钴酞菁（CoPc）和镍酞菁（NiPc），在基底上生长垂直排列的N掺杂碳纳米管。它们通常具有竹状结构，直径在15 - 80纳米范围内。随着XPS的光子能量从475电子伏特增加到1265电子伏特，N含量增加到8原子%，表明纳米管内部的N浓度更高。我们确定了三种类型的N结构：类石墨、吡啶类和分子N₂。吡啶类N结构在内壁处变得显著。分子N₂会以插层形式存在于中空内部附近。XPS价带分析表明，吡啶类N结构诱导金属行为。与使用FePc和CoPc生长的碳纳米管相比，使用NiPc生长的碳纳米管含有更高含量的吡啶类结构，因此它们表现出更多的金属特性。
