液相合成和表征多组分异质纳米组装复合光催化材料

Nanomaterials,including quantum dots,nanocrystals,graphene,and one-dimensional nanowires and nanotubes possess tunable optical and electrical properties and have been extensively investigated for production of solar fuels such as H2 and hydrocarbone by photocatalytic conversion of CO2 and water. However, the solar conversion efficiency has been limited, primarily because of inefficient energy absorption and charge transfer processes. Novel visible-light-driven photocatalytic materials are therefore needed for more efficient utilization of the visible light solar spectrum, along with fast charge separation and transfer. This multidisciplinary proposal seeks to develop novel hierarchically assembled heterostructured nanoarchitectures for use as novel visible light photocatalysts for solar fuel production...The proposal is motivated by preliminary results obtained by the investigators on the photocatalysis and the synthesis and assembly of semiconducting quantum dots (QDs), one-dimensional titanium dioxide nanotube/nanowire arrays, and graphene. The photocatalysts designed using unique hierarchical heterostructured nanoarchitectures of multilayer QDs and/or nanocrystals assembled onto the surface of one-dimensional titanium dioxide nanotube/nanowire arrays or graphene can result in significantly enhanced efficiency and cost-effective utilization of the solar radiation. A comprehensive research program is planned consisting of the following components: synthesis and assembly of novel nanostructured photocataysts, structural characterization, physical property measurements, theoretical studies and evaluation of photocatalytic activity. The intellectual merit of the research lies in the creation of novel hierarchically assembled heterostructured nanoarchitectures that possess band gaps with tunable energy gradients and well coupled band structures for efficient absorption over the entire visible light solar spectrum. Additionally, the structural organization will result in fast generation along with efficient separation and transfer of the photogenerated carriers for significantly reducing carrier recombination...Besides, the materials designed for highly efficient visible light photocatalytic application, the methodologies developed for designing and fabricating advanced materials with multiple components, complex structure, and integrated functionality can be extended to the assembly of a wide range of other inorganic functional nanoparticles materials to form ordered nanoarchitectures that can display novel collective behavior and function for different applications.

本项目借助自组装与外场辅助微控耦合技术，重点围绕石墨烯、一维纳米结构和具有能带梯度的"彩虹"量子点及其组装构筑多组分异质纳米复合可见光光催化材料。研究量子点及其组装的组成和微结构对能带和光性质的影响规律；发展先进液相化学法制备量子点、石墨烯和一维纳米结构,获得控制材料性质的关键合成条件参数。建立外场辅助自组装微控新技术，在石墨烯和一维纳米结构表面精密构筑多组分量子点、纳米晶的有序组装。通过系统研究基元组成、微结构对异质纳米组装的光吸收性质的影响规律、载流子在体相、表面和界面的激发和传输，揭示异质纳米组装因纳米表面效应、量子尺寸效应及纳米基元相互作用而产生的新奇叠加性质和多功能。建立基于材料纳米化、表面纳米结构化、"彩虹"量子点组装的多组分异质纳米组装来设计新型可见光光催化材料的理论和新方法，拓展光催化材料的设计理论和研究对象。

面对日益严峻的能源消耗和环境污染问题，发展高效太阳能转换与存储技术是实现环境保护，社会经济可持续性发展的重要途径。然而，新型非硅太阳能电池和锂离子电池还存在能量转换效率低、电池容量低、使用效率及稳定性等瓶颈问题。本项目面向太阳能转换和存储应用，通过凝练和解决材料制备与应用过程中的关键科学技术问题，发展新型纳米能源功能材料，为设计制造器件新型非硅太阳能电池和锂离子电池奠定基础。.项目研究内容以硫化物纳米晶、石墨烯、一维氧化钛纳米结构为目标材料，研究材料的液相可控合成及组装技术；材料微结构设计和界面优化，实现在石墨烯、一维纳米结构表面构筑多元异质纳米组装，设计新型多组分异质纳米复合材料；研究不同组分材料的界面作用机制、纳米基元的组成、尺寸、晶体结构参数在调控异质纳米结构的光学、电学和磁学性能中的规律，设计和制造基于多组分异质纳米结构的能量转换与存储电极材料和器件。项目经过实施，取得了一系列基础研究成果。.（1）高度有序一维纳米结构的制备及调控。建立了水热晶种诱导制备一维TiO2纳米线/管材料的方法，揭示了晶面诱导剂、反应温度、反应时间等对一维材料晶体结构、形貌、尺寸等微结构的影响规律，首次制备出具有新型金红石和锐钛矿晶型结构的双侧纳米线结构薄膜材料，具有高效传输载流子，陷光性能等特点，光电效率达到5.61%左右。.（2）单分散纳米材料的可控制备。研究了硫化物半导体材料微结构的调控规律及光-电-磁性能。研究发现了低维、形貌、晶体取向性等显著影响材料能带及光电性质的规律等；基于理论分析与实验，建立了材料“微结构-电子传输性能”的关系；首次合成出尖晶石结构的CdCr2S4磁性纳米晶体，系统研究了尖晶石结构纳米晶体的合成条件、磁性能等。.（3）精密构筑了量子点/纳米线的复合结构。对材料的表-界面处电子-空穴传输和分离的机制进行研究。精密构筑了量子点/纳米线复合机构。研究发现，二氧化钛材料荧光共振的可见光能量会直接被量子点材料吸收，总体上提高了整个电池的能量利用效率，光电转换效率是提高到1.2-1.3倍。.（4）石墨烯基锂离子电池电极材料。以绿色无毒廉价的还原剂，获得了高质量石墨烯材料；构建了正负极材料/石墨烯的三维网络结构，促进了锂离子在锂离子电池循环过程中的在三维方向上的迁移和扩散，有效的解决了正负材料在可逆充放电过程中体积变化、极化现象，大幅度提升了正负极材料的电池容量。