氧化物半导体复合纳米贵金属的界面微观结构调控及其协同催化性能研究

Using solar energy for water splitting has been a focus of great attention as a possible means for converting solar energy to chemical energy in the form of clean and renewable hydrogen fuel, which is of great significance for solving the environment problems as well as energy crisis. By applying the development of efficient and stable catalyst as a starting point, this project aims to improve hydrogen production on photocatalysts for water splitting by composite semiconductor hierarchical structures with noble metal nanoparticles. The overall photocatalytic water splitting reaction performance improve for three major reasons: (i) better absorption of light by semiconductor and noble metal nanoparticles to generate electron-hole pairs, (ii) faster charge separation and migration to the surface of semiconductor, and (iii) more active sites for surface reactions of water reduction or oxidation. The combination of special structure and synergetic effect between noble metal and semiconductor can give rise to the great improvement of H2 evolution rate and solar efficiency. The interfacial micro-/nano-structures between noble metal and semiconductor hierarchical structures will be tuned and controlled via changing the size, morphology and composition of noble metals and varying the morphology and structure of semiconductor. Simultaneously, experimental observations of the proposed charge transfer mechanism across the semiconductor/metal junctions and the resultant activity enhancement will be discussed. And theoretical modelling of semiconductor electronic structures at interfaces will be done to explain the functionality of the junction structures. We expect our state-of art catalysts designs will led to advances in understanding of light-induced charge separation and migration as well as subsequent catalytic water oxidation and reduction reactions. More importantly, this proposal work will help us to understand the synergetic catalytic performances between noble metal and semiconductor in depth.

利用光能分解水形成洁净、可再生、高能量密度的氢燃料对解决能源紧缺、减小环境污染具有重大意义。本项目以研发高效、稳定的可见光分解水制氢催化剂为切入点，从提高催化剂对光能的吸收利用，加速光生载流子的分离和迁移，提供更多催化还原位点的角度出发，设计了贵金属纳米粒子和氧化物半导体多级结构复合材料，以新颖合成路线实现二者的优化复合及强化的协同效应。本项目将重点研究通过改变贵金属的尺寸、形貌和组成，以及半导体种类、形貌和结构，调控贵金属与半导体间界面微观结构，探讨其催化性能。同时，结合先进的表征手段和理论计算，探讨催化过程中电子迁移和能量传输机理，以及贵金属纳米粒子与半导体间的作用，揭示两种材料的协同催化作用机制。以期实现对反应机理更加深入的理解。这将为光催化解水反应奠定应用基础，具有重大的科学意义。

光解水制氢是开发利用氢能的重要途径，现有光催化剂存在材料不稳定、效率较低等问题，限制了实际应用。本项目以研发高效、稳定的光催化剂为切入点，从提高催化剂对光能的吸收利用，加速光生载流子的分离和迁移，提供更多催化还原位点的角度出发，设计了氧化物半导体多级结构材料。重点研究了半导体种类、形貌和结构，界面微结构，探讨其催化作用机制。尤其是光催化材料进行精确的形貌和组成设计是提高其光转换效率的有效手段。针对这一问题，本课题利用中空多壳层结构（Hollow Multi-shelled Structures,HoMSs）材料为提高光功能材料的光吸收能力提供了一种崭新的思路。.重要成果如下：（1）采用水热的方法，以TiO2多壳层中空材料为原料，原位将TiO2转变为SrTiO3，并保持形貌不变。通过调节水热时间，调控它们的含量。最后，通过控制水热过程中的溶剂种类，还可以调控SrTiO3晶粒的暴露晶面。HoMS结构的多级壳壁可以有效散射入射光，通过限域效应有效增强光催化剂对光的利用率。经过光催化分解水系统的测试，负载了助催化剂的SrTiO3-TiO2 HoMSs能够稳定的以化学计量比分解纯水。得益于钙钛矿SrTiO3稳定的微/纳结构，该光催化剂能够保持超1天的循环稳定性。（2）进一步，在水热过程合成SrTiO3 HoMSs的过程中加入La3+和Rh3+离子，将两种元素掺杂到SrTiO3晶格中，最终得到了壳层数可调SrTiO3:La,Rh HoMSs。通过控制溶液pH和引入GO制备了BiVO4纳米片作为OER催化剂，最终构筑了在可见光下实现全水分解的Z型光催化剂。催化剂拥有 46.2 µmol h−1 的产氢速率 和 22.3 µmol h−1 的产氧速率 ，在全水分解的条件下，太阳能到氢能的转化效率为0.08%。（3）在简便普适的“次序模板法”基础上，调控金属离子（Ti、Cu）比例的次序分布，制备出内外壳层异质的中空多壳层结构，最终实现三维HoMSs材料对不同波长的入射光的次序吸收。所得四壳层TiO2-CuxO空心球能够以2490 μmol/h的速度光催化析氢超90 h，与之相应的三壳层CeO2-CeFeO3空心球的光催化产氧速率可达452 μmol/h，并且该催化体系能够在氧化还原对的辅助下实现模拟太阳光下的全水分解。