One-step solvothermal preparation of Bi-Bi2O3 -BiOBr ternary complex and its visible light-driven catalytic degradation of methylene blue
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摘要: 构建表面等离子体共振(SPR)、氧空位、异质结是提升半导体光催化剂催化活性的有效方式之一。本文通过改变Bi(NO3)3与KBr的摩尔比，采用一步溶剂热法合成了具有SPR效应和氧空位的Bi-Bi2O3-BiOBr三元异质结复合材料。利用XRD、电子顺磁共振(EPR)、 XPS、SEM、TEM、UV-vis等手段对所得产物的晶相、元素组成和微观形貌进行表征分析，考察Bi(NO3)3与KBr的摩尔比对三元复合物可见光驱动光催化降解亚甲基蓝(MB)活性的影响。结果表明Bi-Bi2O3-BiOBr的催化活性依赖于Bi(NO3)3与KBr的摩尔比，但高于纯Bi2O3和BiOBr。Bi(NO3)3与KBr摩尔比为2∶1制备的2∶1-Bi-Bi2O3-BiOBr对MB展现了最佳光催化活性：在240 min的可见光照射下， 2∶1-Bi-Bi2O3-BiOBr上对MB的去除率为95.07%，降解动力学符合准一级动力学，降解速率常数为2.90 h−1，分别是纯Bi2O3和BiOBr的5与6倍，经4次循环实验后，2∶1-Bi-Bi2O3-BiOBr复合材料对MB的除去效率没有显著的降低。该物质优异的可见光光催化活性催化机制可归结为SPR效应、半导体异质结结构和氧空位的3种协同作用。本文合成特殊结构光催化剂的方法可推广到其他催化材料。Abstract: The construction of surface plasmon resonance (SPR), oxygen vacancies, and heterojunctions is one of the effective ways to enhance the catalytic activity of semiconductor photocatalysts. In this paper, Bi-Bi2O3-BiOBr ternary heterojunction composites with SPR effect and oxygen vacancies were synthesized by a one-step solvothermal method by changing the molar ratio of Bi(NO3)3 to KBr. Used XRD, electron paramagnetic resonance (EPR), XPS, SEM, TEM, UV-vis and other means to characterize and analyze the crystal phase, elemental composition and microscopic morphology of the obtained product, and investigate the effect of the molar ratio of Bi(NO3)3 to KBr on the visible light-driven photocatalytic degradation of methylene blue (MB) activity of the ternary complex. The results show that the catalytic activity of Bi-Bi2O3-BiOBr depends on the molar ratio of Bi(NO3)3 to KBr, but is higher than that of pure Bi2O3 and BiOBr. The 2∶1-Bi-Bi2O3-BiOBr prepared with a molar ratio of Bi(NO3)3 to KBr of 2∶1 exhibited the best photocatalytic activity towards MB. 2∶1-Bi-Bi2O3-BiOBr was irradiated with visible light for 240 min. The removal rate of MB on Bi-Bi2O3-BiOBr is 95.07%, and the degradation kinetics conform to pseudo-first-order kinetics. The degradation rate constant is 2.90 h−1, which is 5 and 6 times that of pure Bi2O3 and BiOBr, respectively. After 4 cycles of experiments, 2∶1-Bi-Bi2O3-BiOBr composite does't significantly reduce the removal efficiency of MB. The excellent visible-light photocatalytic activity of this material can be attributed to the three synergistic effects of SPR effect, semiconductor heterojunction structure and oxygen vacancies. The method for synthesizing photocatalysts with special structures in this paper can be extended to other catalytic materials.
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Key words:
- solvothermal method /
- BiOBr /
- photocatalysis /
- oxygen vacancies /
- heterojunctions /
- semiconductor photocatalysts
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图 1 Bi2O3、1∶1-Bi/BiOBr、2∶1-Bi-Bi2O3-BiOBr、3∶1-Bi-Bi2O3-BiOBr和4∶1-Bi-Bi2O3-BiOBr样品的XRD图谱(a)与局部放大图谱(b)
Figure 1. XRD patterns of Bi2O3, 1∶1-Bi/BiOBr, 2∶1-Bi-Bi2O3-BiOBr, 3∶1-Bi-Bi2O3-BiOBr and 4∶1-Bi-Bi2O3-BiOBr (a) and partial enlargement (b)
图 2 1∶1-Bi/BiOBr、2∶1-Bi-Bi2O3-BiOBr复合物的EPR图谱
Figure 2. EPR spectra of 1∶1-Bi/BiOBr、2∶1-Bi-Bi2O3-BiOBr composites
g—
图 3 (a) 样品2∶1-Bi-Bi2O3-BiOBr的XPS全谱图；Br3d (b)、O1s (c)、Bi4f (d)的高分辨率XPS图谱
Figure 3. (a) XPS survey spectrum of 2∶1-Bi-Bi2O3-BiOBr; XPS spectra of Br3d (b), O1s (c) and Bi4f peak (d)
图 4 样品Bi2O3 ((a), (b))、1∶1-Bi/BiOBr ((c), (d))和2∶1-Bi-Bi2O3-BiOBr ((e), (f))的SEM图像
Figure 4. SEM images of Bi2O3 ((a), (b)), 1∶1-Bi/BiOBr ((c), (d)), 2∶1-Bi-Bi2O3-BiOBr ((e), (f))
图 5 样品Bi2O3 ((a), (b))、1∶1-Bi/BiOBr ((c), (d))、2∶1-Bi-Bi2O3-BiOBr ((e), (f))的TEM图像
Figure 5. TEM images of Bi2O3 ((a), (b))、1∶1-Bi/BiOBr ((c), (d)) and 2∶1-Bi-Bi2O3-BiOBr ((e), (f))
图 6 样品Bi2O3、1∶1-Bi/BiOBr、不同比例Bi-Bi2O3-BiOBr的UV-vis DRS图谱(a)和带隙图谱(b)
Figure 6. UV-vis DRS spectra (a) and plots (b) of (αhv)1/2 versus hv for Bi2O3、1∶1-Bi/BiOBr and different ratios of Bi-Bi2O3-BiOBr composites
图 7 样品Bi2O3、1∶1-Bi/BiOBr、2∶1-Bi-Bi2O3-BiOBr的瞬时光电流图谱(a)和PL光谱(b)
Figure 7. Transient photocurrent responses (a) and PL spectra (b) for different samples of Bi2O3, 1∶1-Bi/BiOBr, 2∶1-Bi-Bi2O3-BiOBr
图 8 样品光降解亚甲基蓝(MB)曲线图(a)和反应速率常数图(b)；2∶1-Bi-Bi2O3-BiOBr和2∶1-Bi-Bi2O3-BiOBr-P(物理法制备)在可见光条件下降解MB (c)；2∶1-Bi-Bi2O3-BiOBr在可见光条件下的循环实验 (d)
Figure 8. Photocatalytic degradation curves (a) of methylene blue (MB) and reaction rate constants k (b) for samples; (c) Photocatalytic degradation of aqueous MB using 2∶1-Bi-Bi2O3-BiOBr and 2∶1-Bi-Bi2O3-BiOBr-P (physical preparation) under visible light irradiation; (d) Cycling runs of 2∶1-Bi-Bi2O3-BiOBr composite under visible light irradiation
图 9 (a) 不同捕获剂对2∶1-Bi-Bi2O3-BiOBr光催化剂光降解MB性能的影响； (b) 缺陷型Bi-Bi2O3-BiOBr纳米复合材料在可见光照射下去除MB光催化机制
Figure 9. (a) Effect of different scavengers on 2∶1-Bi-Bi2O3-BiOBr photocatalytic degradation MB performance; (b) Mechanism for aqueous MB removal catalyzed by defective Bi-Bi2O3-BiOBr nanocomposites under visible light irradiation
SPR—; VB—; CB—; OVS—; BQ—; IPA—; AO—
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