可见光催化剂钒酸铋的可控合成及性能研究

doi:10.15541/jim20180257

摘要/Abstract

摘要：

采用微波水热法, 以BiVO₃·5H₂O和NH₄VO₃为原料, 通过调控前驱液pH可控合成了不同晶体结构的可见光催化剂BiVO₄。利用X射线衍射(XRD)、紫外-可见漫反射(UV-Vis)、拉曼光谱(Raman)和场放射扫描电镜(SEM)等手段对所制备的样品进行了表征和分析, 探讨了不同晶体结构BiVO₄的形成机理; 同时以亚甲基蓝和一氧化氮为降解对象, 考察了样品的光催化性能。结果表明, 当前驱液pH为3~5时, 制备的BiVO₄为四方锆石结构(z-t), 形貌为微米球; 前驱液pH小于2或大于7时, 制备的BiVO₄为单斜白钨矿结构(s-m), 形貌为多面体。这可能是由于前驱液pH的变化, 致使前驱液中钒酸根离子和铋离子的存在形式发生了转变, 进而影响BiVO₄的形成历程, 使得BiVO₄样品的晶体结构、形貌、晶面裸露以及VO₄四面体等发生了改变。光催化试验结果表明, BiVO₄(s-m)光催化活性优于BiVO₄(s-t)。当前驱液pH为9时, 制备的BiVO₄(s-m)样品由于结晶度高、 (040)晶面暴露率高和VO₄四面体畸变程度大, 表现出优异的光催化活性。

关键词: BiVO₄, 微波水热, 可控合成, 光催化

Abstract:

Visible-light-driven photocatalyst BiVO₄ was synthesized via a facile microwave-hydrothermal method using BiVO₃·5H₂O and NH₄VO₃ as raw materials. Crystal structure of BiVO₄ photocatalyst could be selectively controlled to be tetragonal or monoclinic by simply adjusting the pH of the precursor solution. The prepared samples were characterized by XRD, UV-Vis, Raman, and SEM. The mechanism of BiVO₄ formation with different crystal structures was discussed. Meanwhile, the photocatalytic performances of the prepared sample were evaluated by degradation of methylene blue and photocalytic oxidation of NO gas in air under visible light irradiation. The results showed that BiVO₄(z-t) microsphere was obtained when the precursor pH is 3-5, but when the pH is less than 2 or greater than 7, the as-prepared powders are BiVO₄(s-m) with polyhedron morphology. This may be due to the change of pH that could form transformation of vanadate and bismuth ion in the precursor solution, and then affect the formation process of BiVO₄, resuting in the change of crystal structure, morphology, crystal surface, and VO₄ tetrahedron of BiVO₄(s-m). The photocatalytic tests indicated that the activity of BiVO₄(s-m) was much better than that of BiVO₄(z-t). The BiVO₄(s-m) sample prepared at pH 9 exhibits excellent visible-light photocatalytic activity, because of its higher crystalline, preferentially exposed facts (040), and higher degree distortion of VO₄^3- tetrahedron.

Key words: BiVO₄, microwave hydrothermal, controllable synthesis, photocatalytic

中图分类号:

O643

李杰,宋晨飞,逄显娟. 可见光催化剂钒酸铋的可控合成及性能研究[J]. 无机材料学报, 2019, 34(2): 164-172.

LI Jie, SONG Chen-Fei, PANG Xian-Juan. Controllable Synthesis and Photocatalytic Performance of BiVO₄ under Visible-light Irradiation[J]. Journal of Inorganic Materials, 2019, 34(2): 164-172.

图/表 12

图1 光催化反应装置示意图(a)和组合滤光片的透射光谱(b)

Fig. 1 Schematic reactor for visible light photocatalytic degradation (a) and transmittance of the combined light filters (b)1: Cylindrical pyrex vessel; 2: Tungsten halogen lamp; 3: Cutoff filter; 4: Reactor; 5: Saturated cupric acetate solution; 6: Petri dish

图2 不同pH条件下制备的BiVO4样品的XRD图谱

Fig. 2 XRD patterns of BiVO4 sample prepared at different pH

图3 BiVO4(s-m)样品的局部XRD图谱

Fig. 3 Local XRD patterns of BiVO4(s-m) samples

图4 不同pH条件制备的纯相BiVO4漫反射(DRS)谱图

Fig. 4 Diffuse reflectance spectra of BiVO4 sample prepared at different pH

图5 不同pH条件下制备的BiVO4 (s-m)的红外光谱(a)和拉曼光谱(b)

Fig. 5 FT-IR (a) and Raman (b) spectra of BiVO4(s-m) sample prepared at different pH

表1 BiVO4(s-m)的拉曼峰位置及V-O键长和半峰宽

Table 1 Raman absorption band position and V-O bond length, FWHM in BiVO4(s-m)

pH	ν_s(V-O)/cm^-1	R₁/nm	S_1(V-O)	ν_as(V-O)/cm^-1	R₂/nm	S_2(V-O)	Valence state of V	FWHM
1	828.57	0.17071	1.3264	708.40	0.17760	1.0431	5.0223	43.80
2	830.12	0.16934	1.3303	708.93	0.17757	1.0443	5.0352	44.71
7	830.83	0.16929	1.3320	710.53	0.17745	1.0478	5.0438	45.49
9	831.19	0.16927	1.3329	710.71	0.17744	1.0482	5.0469	45.93
11	829.76	0.16936	1.3294	709.64	0.17751	1.0459	5.0342	45.41
13	829.42	0.16938	1.3285	708.93	0.17757	1.0443	5.0298	44.04

图6 不同pH条件下制备的BiVO4样品的SEM和HRTEM(pH=9)照片

Fig. 6 SEM images of BiVO4 sample prepared at different pH and HRTEM image of BiVO4 (pH=9)

图7 不同pH条件下BiVO4(s-m)样品的XPS能谱图

Fig. 7 XPS spectra for BiVO4(s-m) samples prepared at different pH

图8 BiVO4(pH 9)样品降解MB的紫外-可见吸收光谱随时间的变化

Fig. 8 Time-dependent UV-Vis absorption spectra of the MB solution in the presence of BiVO4(pH 9)

图9 不同pH下合成BiVO4样品的光催化性能

Fig. 9 Photocatalytic activity of BiVO4 sample prepared at different pH

图10 BiVO4 (pH 9) 光催化降解MB的稳定性

Fig. 10 Stability of BiVO4 (pH 9) catalyst in the degradation of MB

图11 BiVO4光催化降解的NO性能

Fig. 11 Photocatalytic performances of BiVO4 for decomposing NO(a) Blank; (b) BiVO4 (pH 9)

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