氮掺杂洋葱状纳米碳球的制备与表征

Synthesis and characterization of nitrogen-doped onion-like carbon nanospheres

以碳化钙和谷氨酸为原料,通过反应釜一步法在300℃下制备氮掺杂洋葱状纳米碳球,并改变反应物量来调控碳球的尺寸和结晶度。采用扫描电子显微镜、透射电子显微镜、X射线衍射仪、拉曼光谱仪、比表面积测试仪、X射线光电子能谱仪和元素分析仪对所得产物进行表征。结果表明,采用反应釜法能够成功掺杂氮原子进入碳原子晶格中。改变反应物摩尔量能够得到不同形貌的碳球,当碳化钙与谷氨酸的反应物摩尔比为3∶1时,得到尺寸为30~50 nm的洋葱状碳球;增加谷氨酸的摩尔量易于得到直径为60~100 nm的实心无定形纳米碳球;而增加碳化钙的摩尔量,同样得到洋葱状碳球,但结晶程度提升。反应过程中,谷氨酸不仅能够作为反应的引发剂,还能作为氮源和碳源,其热解形成的五元环化合物在碳球形成的过程中起到重要作用,为弯曲石墨片层的形成提供曲率,有利于洋葱状结构的形成。

Nitrogen doped onion-like carbon nanospheres were synthesized at 300 ℃ by a one-step autoclave method using calcium carbide and glutamic acid as reactants. The diameter and crystallinity of the spheres were controlled by varying the amounts of reactants. The products from different amount of reactants were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, specific surface area analysis and X-ray photoelectron spectroscopy and an elemental analyzer. The results suggested that nitrogen atoms can be doped into the carbon lattice successfully by this method. Different morphologies of the carbon spheres were obtained by changing the amounts of the reactants. When the reactant ratio of calcium carbide to glutamic acid was 3∶1, onion-like carbon spheres with a 30-50 nm diameter were obtained. With an increasing amount of glutamic acid, solid amorphous carbon nanospheres 60-100 nm in diameter were obtained, while with an increasing amount of calcium carbide, identical onion-like carbon spheres were obtained with higher crystallinity. During the reaction, glutamic acid act as an initiator as well as a nitrogen and carbon source, and the five-membered ring compounds from glutamic acid play an important role in forming the carbon spheres, because they provide curvature for the graphite layers, resulting in the formation of an onion-like structure.