【作者】 徐婧；

【导师】 朱永法；

【作者基本信息】 清华大学 ， 化学， 2013， 博士

【摘要】 本论文合成了一系列高比表面的共轭材料，并将其应用于环境净化领域，探讨了共轭材料的结构与吸附性能以及光催化性能之间的关系。在吸附方面，我们采用高比表面的二维共轭材料氧化石墨烯(GO)和石墨烯为吸附剂，吸附作用可以依靠其本身片层结构在表面进行，在提高吸附性能的同时还有利于脱附和再生。在光催化方面，我们采用具有共轭结构的可见光光催化剂g-C3N4为研究对象，对其进行了纳米形貌调控，成功制备出了高比表面的g-C3N4纳米片和多孔g-C3N4，纳米结构有利于光生电子空穴的分离以及光生载流子的迁移，因此可以有效地提高g-C3N4的光催化性能。GO和石墨烯对双酚A (BPA)都表现出了优异的吸附性能。Langmuir等温线模型拟合出的GO对BPA的最大吸附量约为87.8mg·g1(25°C，pH=6.0)，且半小时即可达到吸附平衡状态远快于活性碳的吸附速率，石墨烯对BPA的最大吸附量约为181.8mg·g1(29°C，pH=6.0)。GO具有优异的再生使用能力，经过5次循环实验后依然可以保持83%的吸附量。GO和石墨烯对BPA表现出优异的吸附性能主要是由于两者结构中的单层石墨平面内的苯环以及表面的含氧基团，会与BPA分子结构中的两个苯环以及两个羟基基团之间产生π-π作用和氢键作用，这两种吸附作用机理通过FTIR得到了进一步的验证。通过改良的Hummers法制备出了高比表面的单层g-C3N4纳米片。与g-C3N4相比，g-C3N4纳米片拥有了更高的比表面积(87.5m2g-1)，更快的光生电子和空穴的分离效率以及光生载流子的迁移速率，在紫外光、可见光和模拟太阳光下的光催化和光电流响应性能都发生了明显的提高。我们还发现加热回流过程可以有效地除去g-C3N4纳米片的结构缺陷，进一步提高g-C3N4纳米片对目标污染物的吸附性能、促进光生电子和空穴的分离以及光生载流子的迁移，使g-C3N4纳米片拥有更为优异的光催化和光电流响应性能。通过气泡模板法制备了高比表面的多孔g-C3N4，且煅烧升温速率越快，硫脲加入比例越高，多孔g-C3N4的比表面积越大，吸附和光催化性能越好。与g-C3N4相比，多孔g-C3N4拥有丰富的纳米孔结构，更高的比表面积，更快的光生电子和空穴的分离效率以及光生载流子的迁移速率，使其对目标污染物的吸附性能以及在可见光和模拟太阳光下的光催化降解和光电流响应性能都发生了明显的提高。更多还原

【Abstract】 In our work, a series of π-conjugated materials with high surface area wassynthesized and applied in environmental purification. The relationship between thestructure of π-conjugated materials and their adsorption and photocatalystic propertieswas also systematically investigated. We adopted graphene oxide (GO) and graphene asthe adsorbent. The adsorption can directly occur on their lamellar surface due to thetwo-dimensional structure which will improve the adsorption efficiency andrecyclability. We also adopted graphite-like carbon nitride (g-C3N4) as the photocatalyst.Single-layered g-C3N4nanosheets and nanoporous g-C3N4with high surface area weresuccessfully synthesized. Compared with the bulk g-C3N4, nanostructured g-C3N4canexhibit enhanced photocatalytic activity due to the improved separation ofphotogenerated electron-hole pairs and higher efficiency of charge carriers transfer.GO and graphene both showed excellent adsorption capacity for bisphenol A (BPA).The maximum adsorption capacity (qm) of GO for BPA estimated from the Langmuirisotherm was87.8mg·g1at25°C, pH=6.0. And its required contact time to reachadsorption equilibrium was about30min, which was much shorter than that of activatedcarbon. Besides, qmof graphene for BPA estimated from the Langmuir isotherm was181.8mg·g1at29°C, pH=6.0. The GO had good recyclability and could retain about83%of their adsorption ability after five adsorption-desorption cycles. The largeadsorption affinity of GO and graphene for BPA were thought to be attributed to theirsingle-layered graphene planes with aromatic rings and surface oxygen-containinggroups, which can form π-π interaction and hydrogen bonding with the two benzenerings and two hydroxyl groups of BPA, respectively. The adsorption mechanism wasalso proved by the FTIR spectra.Single-layered g-C3N4nanosheets with high surface area were obtained via amodified Hummers method. Compared with the bulk g-C3N4, g-C3N4nanosheets ownedhigher surface area (87.5m2g-1), improved separation of photogenerated electron-holepairs and higher efficiency of charge carriers transfer. Accordingly, the photocatalyticactivity and photocurrent of g-C3N4nanosheets were remarkably enhanced under UV,visible light and simulated solar light irradiation. Moreover, it was found that an additional refluxing process can effectively remove the structural defects of g-C3N4nanosheets. It further increased the adsorption capacity for the target pollutants,improved the separation of photogenerated electron-hole pairs and charge carrierstransfer of g-C3N4nanosheets, which resulted in higher photocatalytic activity andphotocurrent.Nanoporous g-C3N4with high surface area was prepared by a bubble templatemethod. Faster calcination heating rate and higher proportion of thiourea canresult in higher surface area, better adsorption and photocatalytic properties ofnanoporous g-C3N4. Compared with the bulk g-C3N4, nanoporous g-C3N4possessed a higher surface area and pore volume, improved separation ofphotogenerated electron-hole pairs, and higher efficiency of charge carrierstransfer. Accordingly, the adsorption capacity for the target pollutants, thephotocatalytic activity and photocurrent under both visible light and simulatedsolar light irradiation of nanoporous g-C3N4were greatly improved.更多还原