氮掺杂HTi2NbO7纳米片的制备及其可见光催化性能

首先,采用高温固相法制备层状前驱体CsTi_2NbO_7,再通过与硝酸进行质子交换形成层状HTi_2NbO_7;其次,在四丁基氢氧化铵(TBAOH)中剥离层状HTi_2NbO_7以获得HTi_2NbO_7纳米片;然后与尿素混合并高温焙烧;最后成功地得到了氮掺杂的HTi_2NbO_7纳米片光催化剂。使用粉末X射线衍射(XRD)、扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)、X射线光电子能谱(XPS)、紫外-可见漫反射吸收光谱(UV-Vis DRS)以及N_2吸附-脱附测试等方式对所制备样品的晶体结构、形貌、比表面积、孔分布和光吸收能力等进行详细的表征。研究表明,氮掺杂后减小了HTi_2NbO_7的禁带宽度,从而使光响应范围扩展到可见光区域;掺杂的氮原子主要位于Ti_2NbO_7-薄片的间隙位置,并与氢离子化学键合;与N掺杂的层状HTi_2NbO_7相比,N掺杂的HTi_2NbO_7纳米片具有更大的比表面积和更丰富的介孔结构,这是由于钛铌酸纳米片相对松散且不规则的排列。因此,在降解罗丹明B(RhB)溶液时,N掺杂的HTi_2NbO_7纳米片比N掺杂的层状HTi_2NbO_7具有更加优异的可见光催化活性。

Synthesis and Visible-Light-Driven Photocatalytic Activity of Nitrogen-Doped HTi2NbO7 Nanosheet

Firstly, layered CsTi₂NbO₇ was prepared by high temperature solid-state method, and then layered HTi₂NbO₇ was obtained by a proton-exchange reaction treated with HNO₃ solution. Secondly, the obtained layered HTi₂NbO₇ was well dispersed in tetrabutylammonium hydroxide (TBAOH) solution in order to prepare HTi₂NbO₇ nanosheets by exfoliation reaction. Thirdly, the as-prepared HTi₂NbO₇ nanosheets were dried, and then mixed with urea. Finally, nitrogen-doped HTi₂NbO₇ nanosheet photocatalyst was successfully synthesized by heating the above mixture. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Ultraviolet-Visible diffuse reflectance absorption spectrum (UV-Vis DRS) as well as N₂ adsorption-desorption measurements to characterize the crystal structure, morphology, specific surface area, pore distribution and light absorption capacity of as-prepared samples in detail. It was found that the doped nitrogen resulted in an intrinsic narrowing band-gap so as to widen light response region, and the doped nitrogen atoms were mainly located at the interstitial position of Ti₂NbO₇^- sheets and chemically bonded with hydrogen ions. Moreover, compared with N-doped HTi₂NbO₇, N-doped HTi₂NbO₇ nanosheets had a larger specific surface area and richer mesoporous structure due to the relatively loose and irregular arrangement of the titanium niobate nanosheets. Therefore, the N-doped HTi₂NbO₇ nanosheets exhibited higher visible-light photocatalytic activity for degradation of RhB than that for N-doped layered HTi₂NbO₇.