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类型 基础研究 预答辩日期 2017-11-19
开始(开题)日期 2015-12-23 论文结束日期 2017-06-12
地点 化学化工学院新楼315 论文选题来源 国家自然科学基金项目     论文字数 5.9 (万字)
题目 氮化碳结构调控及其光催化性质研究
主题词 氮化碳,模板法,结晶性,异质结,光催化
摘要 作为人类社会不断发展和进步的能源支撑, 煤、石油等化石燃料作为短时间难以再生的资源,随着人类社会的发展而快速的消耗,难以支撑人类社会的未来发展.同时,矿石燃料的消耗带来了一系列的环境问题,因此,寻找清洁可再生的替代能源成为迫切的需求。太阳能是地球上最丰富的一种可再生的清洁能源,但是其自身较低的能量密度阻碍其直接利用,因此,如何有效地利用太阳能成为当前科研工作者研究的热门课题。光催化剂作为将太阳能转化为可直接利用能源的中间介质,在能源转换过程中起着重要的作用。传统的催化剂,比如金属催化剂TiO2、MoS2、ZnO、CdS尽管都取得了相当优异的催化性能,但是也存在很多的问题,例如:催化剂的稳定性(光刻蚀现象)、光吸收的问题(主要为紫外吸收)、催化剂自身具有环境毒性等。 石墨相氮化碳(g-C3N4)作为一种新型的非金属半导体聚合物,由于其独特的化学和电子能带结构(2.7eV),及自身高的物理和化学稳定性和经济环保的特性,使得其在光(电)催化环境净化,水分解产氢(H2)和光电转换有着巨大的潜力。然而,体相g-C3N4催化剂自身仍然存在一些问题,比如:低的比表面积、有限的可见光吸收、光生载流子的快速复合等,严重制约了其光催化性能。因此,如何进一步提高其光催化性能成为亟需解决的问题,针对上述影响g-C3N4光催化活性所存在的问题,引入一些功能化策略,包括:原子掺杂、微纳结构的引入、结晶性/缺陷位点的调控、异质结结构的构建等。这些策略的应用显著的提高了g-C3N4的光催化活性。然而,当前的这些方法仍然存在一些问题和挑战,如:制备过程复杂,较高的成本问题,也阻碍其进一步扩大应用范围。因此,寻找经济环保,简单的制备方法成为当前迫切的要求。本论文旨在通过探索简单有效的功能化途径,实现g-C3N4在光催化领域的广泛应用。基于此,我们补充并发展了绿色模板法,质子诱导法,同质异质结结构构建以及铁氮掺杂碳材料复合等功能化方法有效地提高了g-C3N4的光电转换效率及光催化活性。主要研究内容列举如下: 1. 通过CaCO3模板法制备了多孔结构的g-C3N4,通过活性位点的增加,有效地提了光电转换效率。传统的模板法是利用商业化的SiO2模板剂,制备有序的介孔g-C3N4催化剂,有效地提高了其光电转换效率,然而去除SiO2模板剂需要用到HF/NH4F溶液,该过程不仅带来一定的危险性和环境污染,还会对催化剂的结构造成破坏,同时商业化的SiO2成本较高,因此,该方法不利于大规模制备催化剂。本工作通过引入工业化的CaCO3纳米粒子作为模板剂,成功的制备出了具有高光电转换效率的多孔g-C3N4催化剂,该方法绿色环保,经济性,为大规模制备高效的光催化剂提供了有效的途径。 2. 利用在酸性条件下,质子诱导实现中间结构单元之间无序的氢键向有序的氢键重排,从而制备高结晶性的g-C3N4光催化剂,实现结晶性/缺陷位点的调控,有效改善g-C3N4的催化活性。基于g-C3N4的聚合过程,首先,我们通过质子诱导调控中间结构单元的排列顺序,然后二次热聚合从而获得各向异性的g-C3N4催化剂。有序的结构提高了催化剂自身的结晶性,减少缺陷位点的数量,从而有效地抑制了光生载流子以缺陷位点为复合中心而导致的快速复合,大大的提高了光催化性能,快速实现了污水净化处理。该方法表明可以通过调控结晶性/缺陷位点数量来实现催化活性的提高。 3. 基于不同形貌的g-C3N4电子能带结构上的微小差异构建异质结结构,实现光生载流子的有效分离,显著提高其光催化水分解产氢(H2)的效率。不同于先前报道的利用其它的半导体催化剂构建异质结结构(TiO2/g-C3N4, BiVO4/ g-C3N4),本文主要是基于不同的前驱物制备的g-C3N4形貌上的差异(纳米片和纳米颗粒),引起电子能带结构的微小差异,从而成功的构建了同质异质结结构,与相比之前报道的异质异质结结构相比较,由于二者在功函数,晶格结构和化学成分等方面几乎完全相同,异质结的界面结构得到进一步优化,更加有效的实现了光生载流子的分离,从而获得更加有效地光催化水分解产氢(H2)活性。 4. 通过湿化学法构建 (Fe-Mp-N-C/g-C3N4) 复合物,显著提高水分解析氢(H2)催化活性。通过铁和氮共掺的方式,不仅有效提高了碳材料的导电性,而且增强了碳材料的金属特性,从而增加C/g-C3N4复合物的肖特基能垒效应,前者加速光生电子由催化剂迁移到到碳材料表面,后者有效抑制光生电子-空穴对的快速复合,二者共同促进光催化活性的提高。
英文题目 REGULATION AND RESEARCH OF CARBON NITRIDE STRUCTURE AND ITS PHOTOCATALYTIC PROPERTIES
英文主题词 template method, crystallinity, heterojunction, photocatalysis, Schottky junction
英文摘要 As the energy support of continuous development of human society, coal, oil and other fossil fuels which are not renewable resources in a short time, with the rapid consumption of human society development, has been difficult to support the further development of human society. Meanwhile, the consumption of fossil energy brought a series of environmental problems; therefore, looking for the clean and renewable alternative energy has become an urgent need. Solar energy is one of the most abundant renewable energy in the world, but its own low energy density hinders its direct utilization. Therefore, how to make use of the solar fuel has been becoming the hot topic for research workers. As the intermediate medium for the conversion of solar energy into the high energy density energy, photocatalysts play an important role in energy conversion process. Conventional photocatalysts, such as metal catalysts: TiO2, MoS2, ZnO, CdS, has obtained excellent catalytic activities, but still faces some challenges, such as: the stability of catalyst (photocorrosion), the limited visible light absorption (mainly UV absorption), the environmental toxicity of the catalyst and so on. Graphitic carbon nitride (g-C3N4) is a new type of metal-free semiconductor polymer. It has huge potential in (photo)catalytic environment purification, water splitting and photoelectric conversion due to its high physical and chemical stability, low-cost and unique electronic band structure (2.7eV). However, the bulk g-C3N4 catalyst still faces some problems, such as low surface area, limited visible light absorption and rapid recombination of photogenerated carriers, which severely restricted its photocatalytic performance. How to further improve its photocatalytic activities is an urgent problem. In order to overcome these restricted factors, some functional strategies include atomic doping, micro/nanostructure design, crystalline/defect sites control and construction of heterojunction structure. The application of these strategies significantly improved the photocatalytic activities of g-C3N4. However, these methods still had some disadvantages, such as complex preparation process, high cost and environmental pollution. These problems restricted their further application. Therefore, looking for economic and environmental functional method is our urgent requirements. In this paper, we aim to realize the the wide application of g-C3N4 in the photocatalysis field by exploring the simple and effective functionalization method. Based on this, we supplemented and developed the green template, proton induced, construction of homogeneous heterojunction and iron-nitrogen doped carbon material composite to effectively to improve the photoelectric conversion efficiency and photocatalyitic activities of g-C3N4. The main research contents are listed as follows: 1. The porous g-C3N4 was prepared through CaCO3 template method and the photoelectric conversion efficiency was effectively improved by the increase of active sites. The porous g-C3N4 was often prepared by using commercially available SiO2 template. This strategy can obviously improve the photocatalytic performance of g-C3N4. However, the removal of SiO2 template often requires HF/NH4F solution, which not only brings a certain risk and environmental pollution, but also destructs the structure of catalyst. Meanwhile, it is not conductive to large-scale application due to the high cost of commercial SiO2. In this work, the high photoelectric conversion activity of porous g-C3N4 has been successfully prepared by introduction of industrial CaCO3 nanoparticles. This method is economic and environmental, which provides an effective way for large-scale preparation of high efficient photocatalyst. 2. The high efficient g-C3N4 catalyst with high crystallinity was prepared by using proton-induced hydrogen bond ordered rearrangement of intermediate structure units to regulate the crystallinity/defect sites under acidic conditions. Based on the polymerization process of g-C3N4, we first obtained ordered intermediate structure units through proton-induced hydrogen bond rearrangement, and then secondary thermal polymerization for anisotropic g-C3N4. The ordered structure improves the crystallinity of catalyst and reduces the number of the defect sites. Therefore, it effectively inhabits the rapid recombination of photogenerated carriers when taken the defect sites as recombination center. It greatly improves the photocatalytic performance, such as: the fast realization of the sewage purification treatment. Thus, this method shows that the photocatalytic activity can be enhanced by regulating the crystallinity/defect sites. 3. The heterojunction structure was constructed based on the small electronic structure difference due to the different morphology of g-C3N4. The hydrogen evolution rate was enhanced by effectively suppressing the recombination of photogenerated electrons and holes. Different from the previously reported heterojunction structure (TiO2/g-C3N4, BiVO4/ g-C3N4), we constructed homogeneous heterojunction structure based on the different morphology of g-C3N4 (nanosheet-like and nanoparticles). The successful construction of homogeneous heterojunction based on the small electronic structure difference due to the morphology difference. Compared with the reported structure, the interface of heterojunction was further optimized due to the similar work function, lattice structure and composition. Therefore, the hydrogen evolution rate was significantly improved due to the more effective separation of photogenerated carriers. 4. The Fe-Mp-N-C/g-C3N4 composite was fabricated by simple wet chemistry and its hydrogen evolution performance was improved remarkably. The co-doping of iron and nitrogen not only improved the conductivity of carbon material, but also enhanced its metal characterization. The improved conductivity of g-C3N4 composites accelerated the migration of photogenerated electrons from photocatalyst to the surface of carbon material. Meanwhile, the enhanced metal characterization further suppressed the recombination of photogenerated carriers through Schottky barriers. Both of them promoted the improvement of photocatalytic activities.
学术讨论
主办单位时间地点报告人报告主题
主办单位 刘松琴教授课题组 2014年10月18日 老化工楼大会议室 王建海 基于碳酸钙纳米粒子绿色环保制备高光电活性多孔氮化碳
东南大学化学化工学院 2016年10月18日 新化工楼315会议室 张向阳 Modern mass spectrometry beyond “-omics”
东南大学化学化工学院 2016年06月02日 九龙湖校区第一教学楼111 Markus Antonietti Carbon Nitride and its family: a game changer on materials chemistry
东南大学化学化工学院 2016年05月13日 九龙湖校老楼307 黄进 纤维素纳米晶的表面修饰及改性材料高性能化探索
东南大学化学化工学院 2016年04月19日 九龙湖校老楼307 Menny Shalom Carbon Nitride and nickel-based materials for artificial photosynthesis
主办单位 刘松琴教授课题组 2017年3月24日 新化工楼315会议室 王建海 通过湿化学法构建 (Fe-Mp-N-C/g-C3N4) 复合物,显著提高水分解析氢(H2)催化活性
主办单位 刘松琴教授课题组 2016年08月02日 新化工楼503室 王建海 基于不同形貌的g-C3N4电子能带结构上的微小差异构建异质结结构,提高其光催化水分解产氢(H2)的效率。
主办单位 刘松琴教授课题组 2015年04月10日 新化工楼503室 王建海 质子诱导氢键重排制备高结晶性氮化碳光催化剂
     
学术会议
会议名称时间地点本人报告本人报告题目
第九届聚合物功能材料研讨会 2015年07月14日 无锡 通过调控氮化碳结晶性提高其光电化学活性
第二届国际电化学能源技术会议 2016年8月17日 加拿大,温哥华 Enhance the Photochemical Activity of Polymeric Graphitic Carbon Nitride by Regulating its Crystallinity
     
代表作
论文名称
Environment-friendly preparation of porous graphite-phase polymeric carbon nitride using calcium car
Coupling polymorphic nanostructured carbon nitrides into an isotype heterojunction with boosted phot
Crystallinity Modulation of Layered Carbon Nitride for Enhanced Photocatalytic Activities
 
答辩委员会组成信息
姓名职称导师类别工作单位是否主席备注
陈金华 正高 教授 博导 湖南大学
牛利 正高 研究员 博导 长春应用化学研究所
王进义 正高 教授 博导 西北农林科技大学
刘松琴 正高 教授 博导 东南大学
周建成 正高 教授 博导 东南大学
林保平 正高 教授 博导 东南大学
孙岳明 正高 教授 博导 东南大学
      
答辩秘书信息
姓名职称工作单位备注
卫伟 正高 教授 东南大学