表面活性剂调控的银/卤化银纳米结构的可控构筑及其选择性光催化性能研究

Currently, environmental problems associated with organic pollutants have become one of the most overwhelming issues that limit the sustainable development of our society. Photocatalytic degradation of organic pollutants by visible-light-driven photocatalysts has been recognized as one of the most promising protocols to address these challenges, where plasmonic photocatalysts have been attracting increasing interest. Among these, Ag/AgX-based (X= Cl, Br, I) plasmonic photocatalysts have gained particular attention. Recently, we demonstrated that high-performance Ag/AgX photocatalysts could be facilely fabricated via surfactant-assisted fabrication, where traditional single-head single-chain surfactants were used as halide source and regulator for controllable fabrication. In these cases, the investigations focus on the enhancement of catalytic performances, while those focusing on the selective catalytic behaviors have only been met with limited success, although an exploration on this subject will provide new opportunities for a highly efficient photo-elimination of specific target substrates, which is strongly desired to match the requirements of future environmental issues. ..To meet this formidable challenge, we herein propose an original protocol for a controllable fabrication of Ag/AgX of tunable external morphology and internal structure, which might confer Ag/AgX with selective photocatalytic capability towards specific substrates. In our new protocol, instead of using conventional single-head single-chain surfactants, surfactants of distinct configurations, such as single-head double-chain surfactants, single-head multiple-chain surfactants of different hydrophobic tails, and bola-surfactants of different spacers, will be employed to realize a controllable fabrication of more flexibilities and diversities. The effects of surfactant structure, silver sources, and fabrication medium etc. on Ag/AgX morphology and structure will be disclosed. More significantly, we will pay our great attention on the fundamental scientific events of such new-type plasmonic photocatalytic systems, including the electron/energy transfer/transport principles during their selective photocatalytic performances, the correlation between the surface electronic structure, lattice structure, and bandgap structure of Ag/AgCl and their selective photocatalytic performances, the scientific nature of such selective photocatalytic performances and their requirements towards the substrate molecules, etc. This investigation will provide deep scientific insights into the underlying correlations between the fabrication protocol, the Ag/AgX morphology and structure, and their selective photocatalytic behaviors, which will endow us with new opportunities for the innovative development of Ag/AgX-based photocatalysts of strong selective catalytic capability. Our proposal is an important subject of sufficient originality, novelty and creativity worth of support.

本项目拟以表面活性剂调控的构筑技术为手段，以对离子为卤素离子、具有不同疏水尾链长度的单头双尾型、单头多尾型，或具有不同间隔基长度的Bola型表面活性剂等为调控剂和卤源，来实现银/卤化银 (Ag/AgX, X=Cl, Br, I) 纳米结构的可控构筑，研究其对有机污染物的选择性光催化降解性能。将重点关注Ag/AgX的可控构筑规律、其选择性光催化过程中电子/能量的转移/传输规律，其表面电子结构、晶格结构、能带结构与选择性光催化性能的科学关联，其选择性催化的本质及对底物分子的要求等科学问题。该研究将有助于揭示表面活性剂的结构——Ag/AgX的内在结构、表观形貌——选择性光催化性能等的内在关系，为理性设计与可控构筑具有优良靶向性光催化性能的高效表面等离子体光催化剂，提供科学依据与技术支持，具有重要的科学与实践意义，是一个具有很强原创性和颇具特色的构思。

按照计划书所拟定内容和目标，本课题旨在使用具有不同分子结构的对离子为卤素的表面活性剂为调控剂和反应剂，来实现基于Ag/AgX (X=Cl, Br, I)的表面等离子体光催化剂的可控构筑及性能调控。执行期间，我们基于Bola-型、Gemini-型、单头多尾型等表面活性剂调控的方法，实现了零维、一维和二维Ag/AgX材料的可控合成、探究了其催化性能，并从表面电子结构、晶体结构、复合等所引起的光生电子与空穴的分离/传输能力层面，诠释了其构效关系。进一步，以具有二维结构特征的氧化石墨烯(GO)为表面活性剂模板或铰链剂，构筑了超细Ag或Ag/AgX颗粒、Au纳米片、Ag/AgBr/石墨粉等与GO的复合材料，探究了其催化性能的构效关系。此外，我们还对基于铂的复合催化材料进行了研究。.. 主要进展如下：采用具有不同疏水尾链长度的含碘对阴离子的单头四尾型表面活性剂，构筑了片状和截角十二面体状AgI基材料，鉴于其特殊形貌所赋予其良好的光生电子与空穴的分离能力，后者表现出了明显增强的催化活性和优良的稳定性；采用Bola-型和单头单尾型表面活性，实现了类立方体块状和类球状Ag/AgCl的合成，前者表现出了更为优良的催化活性，其富含的高指数晶面所赋予其良好的光生电子与空穴的分离/传输能力对此发挥了重要作用；基于gemini-型、单头双尾型、bola-型以及带pi体系疏水尾链型表面活性剂实现了零维、一维和二维AgBr或AgI基微纳米结构的可控合成；平面型GO发挥类似于表面活性剂的作用，通过光照法合成了具有优良催化活性的超细Ag颗粒/GO复合物，并以此为前驱体通过部分氧化——卤化得到了高性能超细Ag/AgX/GO光催化材料；在经典表面活性剂的辅助下以GO为铰链剂构筑了具有优良催化活性的Ag/AgBr/GO/石墨多元复合材料；在GO的辅助下获得了表现出双阶段催化性能的Au纳米片/GO复合材料；基于卟啉纳米球的自催化铂金属化获得了具有优良可循环性的Pt/卟啉复合催化材料。.. 该研究为银基纳米材料的可控构筑提供了简单便捷、廉价易操作的手段，从电子转移层面揭示了该类材料催化性能的构效关系，也为发展其他贵金属基功能材料提供了契机。