【作者】 耿怡；

【导师】 李恒德； 蔡强；

【作者基本信息】 清华大学 ， 材料科学与工程， 2009， 博士

【摘要】 自组装介孔二氧化硅材料具有特殊的结构优势,包括高比表面,有序的孔道结构和在纳米尺度上精确可控的介观构象和结构参数等。这类材料有望在太阳能电池、光催化、传感器等领域取得广泛的应用。本论文在极稀表面活性剂体系下,通过调节反应物浓度,共溶剂种类等,对合成的介孔氧化硅的微观形貌和结构进行了系统研究。在形貌研究的基础上,将控制合成的单分散纳米介孔氧化硅和双连续相介孔氧化硅作为液态电解质的无机胶凝材料成功的应用到染料敏化太阳能电池领域。主要内容和成果是:在极稀表面活性剂体系中,利用自组装方法合成了小尺寸纳米介孔氧化硅,通过调节反应物浓度,能够在较大范围内控制产物的尺寸(10～100nm)和形貌(单分散小球或连续结构),同时产物具有比表面积高,热稳定性良好等特点。指出纳米尺度介孔氧化硅颗粒的形成与单体硅酸根低聚物和表面活性剂的自组装作用相关。在水-油双相体系下,系统研究了自组装合成的介孔氧化硅材料的形貌特点和结构分类。分别对水-乙醚,水-乙醇体系下合成的氧化硅形貌和反应物条件之间的关系进行了讨论,提出形貌生成的机理。指出表面活性剂堆积因子g的变化以及油水两相在剧烈搅拌过程中产生的非平衡态界面是导致产物的形貌和结构具有多样性的原因。在水-乙醚体系中,利用嵌段共聚物F127作为表面活性剂,合成出新型具有分级结构的双连续相介孔氧化硅材料。材料具有多级孔道结构,将利用该材料制备的复合凝胶电解质分别应用于染料敏化太阳能电池和锂离子电池中,结果显示,准固态电解质具有10-3S·cm-1数量级的离子电导率,同时具有良好的机械强度。将小尺寸介孔氧化硅颗粒作为无机添加剂应用到染料敏化太阳能电池凝胶电解质中,探讨了其颗粒尺寸和形貌对电解质电化学性能的影响。对掺杂氧化硅的聚合物凝胶电解质的导电增强机制进行了简单模拟。利用这种颗粒得到的准固态DSSC的光电转化效率比没有使用介孔氧化硅颗粒固化的电解质的效率提高44%。更多还原

【Abstract】 The advantageous structure characteristics of self-assembled mesoporous SiO2, such as high BET surface area, ordered pore channels, and controllable mesophases and structural parameters in the nanometer range, has provided potential applications in a wide range of field e.g., solar cell, photocatalyst, chemical sensor, etc.The research in this thesis presented a novel approach of synthesizing mesoporous silica particles in a very dilute surfactant system where the micro-morphology and micro-structure of silica particles can be tuned by adjusting the concentration of the reactants and adding various types of co-solvent components. Furthermore the mono-dispersed nano-sized mesoporous silica particles and bicontinuous hierarchical mesoporous silica (BCMS) obtained was added into liquid electrolytes as gelator to form composite gel electrolytes for the application in the dye-sensitized solar cells and lithium battery. The main content and results are presented below.In a very dilute surfactant system, mono-dispersed nano-sized (10~100nm) mesoporous silica particles were synthesized via self-assembly approach. By regulating the reagent concentration, the sizes and morphology (monodisperse particles or the network structure) of the synthesized particles can be controlled over a relatively wide range. The synthesized particles have high surface area and thermal stability. The formation of the nano-sized mesoporous silica particles was proposed to be correlated with the self-assembly reaction between silicate oligomers and surfactant.In the water/oil two-phase system, the morphology and structure of silica particles were classified and investigated systematically, which facilitated the understanding of silica morphosynthesis in the applied system. The relationship between the morphogenesis and reaction conditions was discussed in both water/diethyl ether and water/ethanol systems. A mechanism of morphology formation was proposed. It was suggested that an intrinsic uncertainty factor occurs in the OWTP system. The results indicate that, the evolution of critical packing parameter g and the non-equilibrium interfaces formed by fluid rheological distortions and reconstructive reaction fields played a crucial role in the morph-synthesis process.In the water/diethyl ether system, novel bicontinuous hierarchical mesoporous silica was synthesized with the block copolymer F127 as surfactant. Compared with the traditional nanoparticles or mesoporous silica, BCMS had a unique hierarchical pore structure. It was incorporated into composited gel electrolytes for dye-sensitized solar cells and lithium battery application. The results showed that the quasi-solid state electrolyte has conductivity as 10-3S·cm-1 and good mechanical stability.As inorganic gelators, the nano-sized silica particles were added into the electrolyte of dye-sensitized solar cells. The effects of the size and structure of the particles added were discussed with respect to the electrochemical properties of the electrolyte. A simplified simulation was processed in explaining the improved conductivity. After the introduction of the mesoporous silica particles, the I—3 ion diffusion coefficients and the exchange current density I0 were promoted along with the increase of the photocurrent density and reduction in the dark reaction. Compared to those without mesoporous silica particles, the photo-conversion efficiency of the quasi-solid state DSSC processed in the presented approach was enhanced by 44%.更多还原