【作者】 康文君；

【导师】 钱逸泰；

【作者基本信息】 中国科学技术大学 ， 无机化学， 2011， 博士

【摘要】 本论文旨在探索新颖结构的碳及碳基复合材料的控制合成及性能研究。在高温热解条件下合成了碳/碳核/壳结构的纳米纤维和花状的氮掺杂碳纳米片,在低温水热条件下合成了蠕虫状Pd/C核-壳结构的纳米复合材料,并通过循环伏安法研究了所得样品对生物小分子的电催化性能。论文的主要内容概括如下:1. 600°C下在高压釜中共热解四氢呋喃和二茂铁合成了不同于以往碳纤维结构的碳/碳核/壳结构的纳米纤维,碳纤维直径在50 nm左右,而长度可达几个微米。纳米纤维内核的直径在10 nm左右,壳的厚度在20 nm左右,并且碳核的石墨层与碳壳的石墨层在堆垛方向上是相互垂直的。当在反应体系中引入1 mLH₂O时,得到的产物为空心的六足状碳材料;当反应中只有四氢呋喃时,得到的产物为实心碳球。对比实验证实来源于二茂铁分解产生的金属Fe为碳纤维生长的催化剂。我们根据实验结果,提出了其可能的形成过程。此研究工作已被国际期刊杂志Advanced Materials Research接受。2.在聚丙烯酰胺的存在下,以PdCl₂和α-乳糖为原料在200°C下通过一步水热-碳化过程合成得到蠕虫状Pd/C核-壳结构的纳米复合材料。随着反应温度由140°C升高到200°C,碳壳层的厚度从5 nm增加到40 nm。当PAM或者PdCl₂的用量增加时,会得到球状的Pd/C核-壳结构。我们参照不同时间段产物的结构分析提出了诱捕-还原-碳化的生长机理:聚丙烯酰胺通过配位作用与Pd²⁺结合并形成小的团簇,α-乳糖将Pd²⁺还原为金属Pd,并同时碳化将生成的Pd颗粒包覆起来。这样的合成路线可拓展到球状Ag/C核-壳结构的纳米复合材料合成。循环伏安法研究证实了蠕虫状Pd/C核-壳结构的纳米复合材料对生物小分子抗坏血酸具有电催化活性。此研究工作于2011年发表在国际期刊杂志J. Phys. Chem. C上。3. 700°C下利用反应釜中吡咯和碱式碳酸镁的热解反应制备了花状的氮掺杂碳纳米片。片的尺寸可达几微米,厚度在2-3 nm。通过调控反应温度还得到了管状、带状的氮掺杂碳材料。我们研究了反应温度对氮各种化学态含量的影响:高温条件下石墨型的氮占主导,而低温下吡咯型的氮占主导,且其热稳定顺序为:石墨型>吡啶型>吡咯型。此外,循环伏安研究证实氮掺杂碳纳米片对H₂O₂具有很好的电催化活性,并且其还原电流与扫描速率平方根成线性关系,说明电极过程是受扩散控制的。更多还原

【Abstract】 In this dissertation, controlled synthesis and properties were developed to prepare carbon and carbonaceous composite materials with novel structures. Carbon/carbon core/shell nanofibers and flower-like N-doped carbon nanosheets have been prepared by co-pyrolysis at high temperature. Worm-like palladium/carbon （Pd/C） core-shell nanocomposites have been hydrothermally prepared at low temperature. We also study their electrocatalytic activity toward biomolecules through cyclic voltammetry （CV）. The main points are summarized as follows:1. Carbon/carbon core/shell nanofibers with diameters of ⁵0 nm and lengths up to several micrometres have been prepared by co-pyrolysis of tetrahydrofuran and ferrocene in a stainless steel autoclave at 600°C. The diameter of carbon core is ¹0 nm, and the thickness of carbon shell is ²0 nm. It is found that the graphene layers of carbon core are perpendicular to the ones of carbon shell in stacking orientation. When hollow hexapod-like carbon materials can be obtained with water introduced into reaction system. Moreover, the ferrocene is absence, only solid carbon spheres are observed. Comparative experiments confirm that the metallic iron catalysts, originating from the decomposition of ferrocene, are responsible for the formation of nanofibers. And a possible growth process for the three shaped carbon materials is proposed.2. Worm-like palladium/carbon （Pd/C） core-shell nanocomposites have been hydrothermally prepared starting from PdCl₂ andα-lactose monohydrate （α-LM） in the presence of polyacrylamide （PAM） at 200°C. The thickness of carbonaceous shells varied from 5 to 45 nm with increasing temperature from 140 to 200°C. When the dose of PAM or PdCl₂ was increased, spherical Pd/C core-shell nanocomposites were obtained. Time-dependent experiments confirmed that formation of Pd/C core-shell nanocomposites underwent an entrapment-reduction-carbonization process. Cross-linked PAM clusters with rich -CONH₂ entrap the Pd²⁺ ions in solution by a coordination effect. Then the chelated Pd²⁺ ions are gradually reduced to metallic Pd byα-LM. Finally, carbonization coating occurs on the surfaces of Pd nanoparticles fixed by PAM clusters. Such a route has also been extended to synthesize spherical Ag/C core-shell composites. A cyclic voltammetry （CV） study reveals that the as-prepared Pd/C core-shell nanocomposites exhibit electrocatalytic activity toward oxidation of ascorbic acid （AA）.3. Flower-like N-doped carbon nanosheets with the thickness of 2-3 nm and the sizes up to several microns have been prepared by co-pyrolysis of pyrrole and 3MgCO₃·Mg（OH）₂·3H₂O in a stainless steel autoclave at 700°C. We also obtain N-doped carbon nanotubes and nanobelts when varying the reaction temperature. The influence of reaction temperature on the nitrogen contents and chemical states are also studied. It is found that the graphitic N is dominant at high temperature, while the pyrrolic N is dominant at low temperature. The order of thermal stability follows graphitic N > pyridinic N > pyrrolic N. A cyclic voltammetry （CV） study reveals that the N-doped carbon nanosheets exhibit good electrocatalytic activity toward the oxidation of H₂O₂. A linear relationship between the amperometric responses and the scan rates square-root is observed, indicating that the electrode process is spread control.更多还原