N掺杂过渡金属氧化物单分子层的化学剥离及可见光催化性能

Single-molecule thick nano-materials featuring large surface area, high reaction activity and quantum size effect have received much attentions. The transition metal oxide nanosheets can be fabricated via low-temperature soft chemical routes and they often show highly increased reaction activity and catalytic efficiency. In this work, we will combine the single layer exfoliation methods with the N-doping methods to fabricate N-doped transition metal oxide nanosheets for visible-light photocatalysis. 1) Syntheses of Nb-based perovskite oxides with different layer thickness and their N-doping under NH3 atmosphere; 2) Fabrication of N-doped Nb-based oxide nanosheets by low-temperature topochemical manipulations such as the protonize and subsequent chemical exfolication in solutions; 3) Structural and morphology characterizations of the as-synthesized nanosheets, and their visible-light induced photocatalytic performance. We will finally fabricated a series of thickness-tunable Nb-based oxide single-layered nanosheets with profound catalyses capability under visible light. The investigation will focus on the relationship between the artificial manipulation of crystal structure and electrical structure of a given material and its bulk properties. These studies will also reveal that the effectual combinations of various chemical synthesis methods and denaturation methods can greatly improve the material design techniques, especially for some specific purposes.

单分子层纳米材料具有大的比表面积、高的反应活性以及量子尺寸效应等，在理论研究、薄膜制备、纳米器件组装等领域获得了广泛关注。通过低温软化学方法制备过渡金属氧化物的单分子纳米片层并应用于光催化反应可以极大地提高材料的活性反应位点和催化效率。本项目将单分子层剥离技术和氧化物的氮化改性方法相结合，制备N掺杂的过渡金属氧化物单分子层纳米材料以应用于可见光催化反应：1) 制备具有不同板层厚度（n=3-6）的铌基钙钛矿氧化物并在NH3气氛中进行氮化反应；2) 通过质子化和溶液中化学剥离等低温软化学反应制备N掺杂的铌基氧化物单分子纳米片层；3）结构形貌表征和可见光催化性能研究。本项目将制备出一系列具有优良可见光催化性质的厚度可调的铌基氧化物单分子纳米层，从晶体结构和电子结构的微观调控与材料宏观性质的联系出发，阐述多种化学制备方法和改性方法的结合应用于特殊材料制备的广阔前景。

阴离子掺杂和液相剥离是两种常用的能够提高宽禁带半导体材料光催化活性的方法。前者可以在价带和导带之间引入能级，提高材料在可见光波段的吸收效率；后者可以用于制备单层纳米片结构，极大地提高材料的比表面积和催化活性位点。我们在一类层状钙钛矿氧化物中，将氮化改性与液相剥离技术相结合，制备了一系列氮掺杂的过渡金属氧化物单分子层纳米材料应用于可见光催化裂解水产氢。获得的催化剂材料的特征厚度小于5纳米，对可见光的吸收有明显的提高，与改性前的材料相比产氢速率提高了三个数量级以上。在此基础上，制备了一系列厚度可控的铌基钙钛矿纳米片，研究了在该材料中有利于光生电子空穴对分离的最佳厚度。该项目的研究成果一方面验证了综合运用多种手段改良宽禁带固体催化剂的可行性，获得了一系列优秀的可见光催化剂材料，另一方面为二维催化材料的精确厚度控制提供了重要参考。