高稳定性有序介孔尖晶石AFe2O4(A=Zn,Cu,Co,Ni)的可控制备及可见光催化分解水制氢研究

Compared to nanoparticles, mesopoeous materials possess regular pore structure, high porosity and large surface area. However, it also has low thermal stability and poor crystallinity. In order to resolve it, this project would explore the effective approach for design and synthesis of high stability ordered mesoporous AFe2O4(A=Zn, Cu, Co, Ni). In this project, high stability ordered mesoporous AFe2O4 films were prepared through the evaporation-induced selfassembly (EISA) route, combined with encircling organic amine protectors to restrict the AFe2O4 primary particles, and achieve the effective control of the aggregate and growth for the primary particles under high temperature calcination. While maintaining the liquid crystal mesophase structure of AFe2O4, the crystallinity of the mesoporous wall was also improved, so the high stability ordered mesoporous AFe2O4 was obtained. On the basis of this study, in order further to improve the separation of photoinduced electron-hole and the efficiency of photocatalytic water splitting, cocatalysts (noble metal and semiconductor oxide nanoparticles) were deposited into the mesoporous AFe2O4 by the nanocasting method with the pressure-induced assistance. So the AFe2O4 composites can be constructed. X-ray synchrotron radiation, transient state and steady state technology were used to study the microstructure and electric charge transfer mechanism, disclose the relationship of the catalyst component, structure and performance, and further clarify the mechanism of visible light photocatalytic water splitting for hydrogen production. This study can provide a new way to design new-type visible light catalysts with high stability.

介孔材料与纳米粒子相比具有规整的孔道结构、高的孔隙率和大比表面积等优点，但也存在热稳定性和晶化度较差的问题。本项目拟探索设计与合成高稳定性和高晶化度的有序介孔AFe2O4(A=Zn,Cu,Co,Ni)的有效途径。采用蒸发诱导自组装技术，利用有机胺分子束缚介孔AFe2O4初级粒子，实现高温焙烧时对初级粒子聚集和生长的有效控制，在稳固介孔AFe2O4的有序介观网络结构的同时，提高介孔孔壁的晶化度，最终制备出高稳定性的有序介孔AFe2O4。在此基础上，利用压力诱导辅助纳米铸造法将助催化剂（如贵金属、半导体纳米粒子）沉积到介孔AFe2O4中，以提高可见光催化分解水制氢性能。利用X-射线同步辐射、瞬态与稳态光伏等技术研究高稳定性的介孔AFe2O4及其复合体材料的微结构和电荷传输机制，揭示催化剂组成、结构和性能之间的关系，阐明光催化分解水制氢机制，为设计新型高稳定性可见光催化剂提供思路。

半导体材料的纳米化是提高光催化活性的重要途径之一，尤其是介孔纳米材料在光催化领域有着广泛应用，而纳米化会带来结晶度较低、缺陷较多等问题，提高焙烧温度可以提升结晶度，但会导致晶粒尺寸变大、相变、孔塌陷和比表面积变小等问题，因此如何解决这一问题是当前科研工作者面临的一个挑战。蒸发诱导自组装是一种很有效的制备有序介孔半导体材料的方法，本项目中在采用蒸发诱导自组装策略制备有序介孔尖晶石前躯体的基础上采用有机胺束缚介孔尖晶石初级纳米粒子前躯体，从而达到提高稳定性，抑制生长的目的，并对其内在机制进行了研究，通过该后处理策略制备的材料可以显著提高催化活性，该策略可以拓展应用到提高其他半导体氧化物纳米材料的制备中，该项目始终按照计划展开工作，并已经完成计划内容。同时针对半导体纳米材料在光催化中遇到的光生电荷复合较快、可见光利用率低的问题，并且根据目前国际上在该领域的研究进展，本项目研究范围有所拓展，对尖晶石与金属氧（硫）化物等的复合异质结构进行了制备，对其结构进行调控，并研究成分、结构和性能之间的关系，已经取得一些有特色、有影响的成果，执行情况主要反映在已录用的30余篇SCI收录论文和国家发明专利中，后续研究成果也正投往SCI国际期刊，该项目的完成对于今后在光催化应用领域开展更深入的研究工作有着重要的指导作用和科学意义。