纳米复合材料界面电子转移对光、电催化性能影响的研究

发布时间：2018-01-13 07:49

本文关键词：纳米复合材料界面电子转移对光、电催化性能影响的研究　出处：《上海交通大学》2015年博士论文　论文类型：学位论文

【摘要】：纳米复合材料作为一类重要的功能材料,是经由不同结构单元在微纳尺度或分子水平上复合或组装所形成的一类新型材料。通过复合,各结构单元在性能互补的基础上,可以产生协同效应,从而赋予纳米复合材料独特的性质。纳米复合材料因其独特的结构特点,已广泛应用于人们生活的各个领域。在催化应用领域,纳米复合材料在催化反应过程中,常常与反应物之间或自身各结构单元之间发生界面电子转移的过程,探究纳米复合材料在催化反应过程中界面电子的转移形式,对于调控其催化性能至关重要。基于以上考虑,本论文以催化应用为导向,设计合成了一系列具有独特结构和优异性能的新型纳米复合材料,系统探究了一系列纳米复合材料在催化反应过程中的光、电驱动的界面电子转移过程,旨在建立纳米复合材料界面电子转移与催化性能的关系。论文取得的主要研究结果如下:首先,我们以碳基纳米复合催化剂中碳碳结构单元之间的界面电子转移为研究对象,将天然生物质模板作为原料,合成了“树叶状”氮掺杂石墨烯与纳米碳纤维复合材料(CNF@NG),结构分析发现,氮掺杂石墨烯与纳米碳纤维高度复合,有利于二者间的界面电子转移,保证电子通过纳米碳纤维快速转移至氮掺杂的石墨烯催化活性位点。此外,纳米碳纤维支撑的三维多孔结构有助于反应物质在材料表面的传输。在此基础上,我们将CNF@NG纳米复合材料应用于燃料电池阴极氧还原电催化反应,表现出了非常优异的催化活性、单一的选择性和超高的稳定性。其次,我们以碳基纳米复合催化剂中碳与过渡金属硫化物之间的界面电子转移为研究对象,将一整张氮掺杂石墨烯与纳米碳纤维复合碳纸(CPs)作为基底,在其表面修饰超薄MoS_2纳米片,得到了三维多孔MoS_2-CPs复合碳纸材料。结构分析发现,由于结构单元MoS_2与CPs之间的强相互作用限制了MoS_2纳米片的生长,得到的MoS_2具有超薄且富含大量缺陷的特点,这有利于MoS_2活性边缘的暴露,同时,MoS_2与CPs之间的强相互作用有助于电子在界面间快速转移,促进催化反应的进行。此外,CPs的三维多孔结构有利于反应物质和产物的扩散,很大程度上提高了催化反应的效率。在此基础上,我们将MoS_2-CPs复合碳纸作为大面积工作电极应用于电催化制氢反应中,研究发现无论在酸性和碱性电解液中,MoS_2-CPs均表现出优异的电催化制氢活性,并展现了良好的循环稳定性能。为了证明以尿素热缩聚形成的氮化碳模板合成石墨烯基纳米复合材料的普适性,我们以废纸(如打印纸、滤纸、牛皮纸、餐巾纸、废报纸和挂历纸)为原料,以尿素作为唯一添加剂,一步热处理得到了表面类“树枝状”碳纸复合材料(GCCP)。结构分析发现,GCCP表面特征为氮掺杂石墨烯和纳米碳纤维覆盖微米碳纤维复合结构,形成了一种类“树枝状”的多级分层纳米复合结构,该复合结构赋予了GCCP表面超疏水特性,可以直接用于油水分离应用,且分离效率超过95%;同时,高度石墨化的GCCP展现了优异的导电性能,可以直接作为导电碳纸或复合制成柔性电极使用;此外,GCCP碳纸在一系列电催化反应中表现出了较好的催化活性和优异的稳定性。此外,我们还以介晶复合氧化物催化剂中介晶表面的界面电子转移为研究对象,将介晶BaZrO_3中空纳米球作为模型,通过简单的热处理方式,逐渐改善了空心球壳的晶化程度,得到的高结晶度介晶BaZr O_3中空纳米球具有高效的光解水以及光降解甲基橙能力。研究发现,空心球壳结晶度的提高为光生电子转移提供了高速通道,促进了材料表面的电荷快速分离,从而提高了材料的光催化活性。
[Abstract]:The nano composite material as a kind of important functional materials, through different structural units in a new type of micro nano materials forming composite or assembly scale or molecular level. Through the compound, the structural units based on complementary properties, can produce synergistic effect, thus giving properties of nano composite materials unique nano composite. Material due to its unique structure, has been widely used in all areas of people's lives. In catalytic applications, nano composite materials in catalytic reaction process, the process of interfacial electron transfer occurs between the reactants or its often units between the catalytic reaction process of interfacial electron transfer form of nano composite research materials for the regulation of the catalytic performance is very important. Based on the above considerations, the catalytic application oriented, with a series of unique structure and excellent design and synthesis New type of nano composite material properties, inquiry into a series of nano composite materials in catalytic reaction in the process of light, electric driven interface electron transfer process, aimed at establishing the relationship of nano composite materials interfacial electron transfer and catalytic performance. The main results are as follows: firstly, we at the interface between electrons of carbon structure unit based on carbon nano composite catalyst transfer as the research object, the natural biomass template as raw material, the synthesis of "leaves" nitrogen doped graphene and carbon fiber composite materials (CNF@NG), structure analysis, nitrogen doped graphene and carbon nanofibers highly composite, interfacial electron transfer between the two to the guarantee of electrons through the catalytic site of graphene nano carbon fiber rapid transfer to nitrogen doping. In addition, the three-dimensional porous structure of nano carbon fiber supports help to reactant In the transmission quality of material surface. On this basis, we will apply the CNF@NG nano composite material in cathode oxygen reduction catalytic reaction, showed excellent catalytic activity, selectivity and single high stability. Secondly, we use carbon nano catalytic agent in the interface between electrons and carbon transition the transfer of metal sulfide as the research object, a whole piece of nitrogen doped graphene and carbon fiber composite carbon paper (CPs) as the substrate, the surface modification of ultrathin MoS_2 nanosheets, the 3D porous MoS_2-CPs composite materials. The structure of carbon paper analysis found that, due to the strong interaction between the structural unit MoS_2 and CPs limit MoS_2 nano film growth, the MoS_2 has the characteristics of thin and rich in a large number of defects, which is conducive to the edge of the exposure, the activity of MoS_2 between MoS_2 and CPs at the same time, the strong interaction is helpful for electronic Fast transfer at the interface between, promote the catalytic reaction. In addition, the three-dimensional porous structure of CPs is beneficial to the diffusion of reactants and products, greatly improve the efficiency of the catalytic reaction. On this basis, we will work as a large area of MoS_2-CPs composite carbon paper electrodes for electrocatalytic hydrogen reaction, the study found no matter in acid and alkaline electrolytes, MoS_2-CPs showed excellent electrocatalytic activity for hydrogen generation, and show good cycle stability. In order to prove the formation of urea pyrolysis carbon nitride template synthesis of graphene based nano composite material of the universality, we use waste paper (such as printing paper, filter paper, kraft paper, paper napkin, waste newspapers and paper calendars) as raw materials, using urea as the only additive, a step heat treatment by surface "dendritic" carbon paper composite (GCCP). The structure analysis shows that the surface characteristics of GCCP Cover the micron carbon fiber composite structure for nitrogen doped graphene and carbon nanofibers, the hierarchical nano composite structure forms one kind of "dendritic", the composite structure gives GCCP surface super hydrophobic properties, can be directly used for oil-water separation, and the separation efficiency of over 95%; at the same time, highly graphitized GCCP show the excellent conductive properties, can be directly used as conductive carbon paper or composite made of flexible electrode; in addition, GCCP carbon paper in a series of electro catalytic reaction showed good catalytic activity and excellent stability. In addition, I also have to interface electronic mesogenic compound oxide catalyst of mesogenic surface transfer as research object, the mesomorphous BaZrO_3 hollow nanospheres as a model, by a simple heat treatment, gradually improve the crystallization degree of hollow spherical shell, hollow nanospheres have high crystallinity mesocrystal BaZr O_3 It has the ability of photolysis and photocatalytic degradation of methyl orange. It is found that the increase of crystallinity of hollow spherical shell provides a high-speed channel for photoelectron transfer, and accelerates the rapid separation of charge on the surface of the material, thus improving the photocatalytic activity of the material.

【学位授予单位】：上海交通大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB33;TB383.1

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