【作者】 吴微；

【导师】 刘云凌；

【作者基本信息】 吉林大学 ， 无机化学， 2019， 硕士

【摘要】 介孔碳材料因其高比表面积、高度有序的孔道、以及碳骨架易掺杂原子实现功能化等特点,在催化、光电、生物制药以及储能等领域有着广泛的应用。然而传统的浸渍法合成步骤复杂、担载量低以及分散性差等缺陷限制了介孔碳复合材料的应用和发展。本论文中我们设计了一种温和的配位诱导自组装的方法来合成纳米粒子分散性高、纳米粒子相对尺寸较小的过渡金属-介孔碳纳米复合物。通过原位担载的方法有效解决了金属纳米粒子聚集的问题,在保证高担载量的同时,通过配位键和介孔孔道共同抑制纳米粒子生长,得到纳米粒子分散性高的过渡金属-介孔碳纳米复合材料。我们选择邻苯三酚来合成具有丰富羟基的酚醛树脂前驱体,邻苯三酚的三个酚羟基与金属离子之间较强的配位作用以及多种配位方式不仅能使聚合物前驱体中担载更多金属,而且在进一步碳化的过程中限制纳米粒子的生长。另外,有序介孔孔道的限域作用也在碳化过程中起到抑制纳米粒子的生长和聚集的作用。通过配位诱导的自组装合成策略合成得到的过渡金属-有序介孔碳纳米复合物具有较高的金属担载量(1.25%-7.27%),较小的纳米粒子尺寸(4.3-15.6 nm),以及高比表面积(475-589 m2 g-1)。高孔容量的有序介孔碳为硫的储存提供大量空间,并且担载在孔道中的钴纳米粒子是促进多硫化物转化的有效催化剂,因此Co-有序介孔碳纳米复合物在锂硫电池的应用中表现出较高的电池容量,电流密度为0.1C时,电池容量达1002 m Ah g-1,同时具有良好的循环稳定性,电流密度为0.5C时,400个循环后电池容量仍可维持在初始容量的69%左右。我们通过简单的氨气活化的方法,在过渡金属-有序介孔碳纳米复合物中掺杂氮元素,使其在电解水产氢的催化中有更高的催化活性。由于过渡金属-介孔碳纳米复合物在较高的煅烧温度下依旧可以保持良好的分散性,我们将煅烧温度提高至850oC使产物的介孔碳骨架的石墨化程度提高,从而使其在电化学催化的应用中有更好的导电性。得到的含氮的Co-介孔碳纳米复合物在酸性和和碱性电解液中均表现出良好的电解水产氢催化性能。当电流密度达到10 m A cm-2时,催化剂在0.1M KOH电解液以及0.05M H2SO4电解液中的过电势分别为180 m V和188 m V。由于原位合成得到的金属纳米粒子均嵌于碳孔壁中,有效避免了在电解水反应的催化过程中金属纳米粒子被电解液腐蚀或从介孔孔道中脱离,因此在酸性和碱性电解液中均表现优秀的稳定性,可以维持电流密度10 m A cm-2长达20 h以上。更多还原

【Abstract】 Multifunctional ordered mesoporous carbon materials that feature high surface area,uniform pores,good conductivity of carbon skeletons and specific host-gust interactions,which are of interest for a wide variety of applications,for instance catalysis,photonics,bioscience and energy storage.Here we establish a facile and generalizable “coordination-assisted self-assembly” for encapsulation of aggregationfree and highly dispersed metal nanoparticles inside the mesoporous carbon frameworks.The choice of pyrogallol as phenolic resin precursor is essential for the in situ encapsulation,because the strong coordination between the three hydroxide groups of pyrogallol and metal ions favors the immobilization of transition metal into the mesopores,and then suppress the sintering of metal nanoparticles at high carbonization temperatures.The metal supported mesoporous composites possess the very high loading content of 1.25%-7.27%,tiny particle sizes of 4.3-15.6 nm and high surface area of 475-589 m2 g-1.The unique structure in deed endows high sulfur loading content in the conductive mesoporous carbon channels,and meanwhile metal nanoparticles as catalyst effectively promotes the electrochemical conversion of polysulfides,resulting in a high reversible capacity,excellent rate capability and good cycling stability for Li-S batteries.The N-doped metal-OMC nanocomposites were synthesized through a simple ammonia-active step to dope nitrogen into the metal-OMC nanocomposites,which leads to higher electrochemical catalysis activities of the products.In consider of that the well-dispersed nanoparticles can be maintained under a high pyrolysis temperature,the calcining temperature was lift to 850 oC to get products with higher graphitization level which endows metal-OMC nanocomposites better electroconductivity.The Ndoped metal-OMC nanocomposites exhibit favorable performance for hydrogen evolution reaction(HER)in both acid and alkaline electrolyte.It delivered a current density of 10 m A cm-2 at the overpotential of 180 m V in 1 M KOH and 188 m V in 0.5 M H2SO4 electrolyte.The transition metal nanoparticles embedded in the mesoporous wall were protected from corrosion of electrolyte.Therefore,the nanocomposites exhibit excellent stability.The catalyst could sustain potentiostatic electrolysis for at least 20 hours at 10 m A cm-2 in both acidic and alkaline solutions.更多还原