沉淀法制备Bi_2O_3的晶相转变过程及其光催化性能

以硝酸铋为原料,氨水为沉淀剂,通过液相沉淀法制得前驱体Bi(OH)_3,并将Bi(OH)_3分别在不同温度和时间下焙烧。利用X射线衍射(XRD)、拉曼光谱、热重(TG)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)及紫外-可见漫反射光谱(UV-Vis DRS)详细研究了Bi(OH)_3转变为Bi2O3的过程及相变过程中粒子形貌、大小、光吸收性质等。结果表明,前驱体Bi(OH)_3经过焙烧之后,发生了如下的转变过程:Bi(OH)_3→Bi_5O_7NO_3→β-Bi_2O_3/Bi_5O_7NO_3→β-Bi_2O_3/Bi_5O_7NO_3/α-Bi_2O_3→α-Bi_2O_3,而且转变过程伴随着粒子长大。在上述转变过程中,与Bi_5O_7NO_3向β-Bi_2O_3转变的过程相比,从β-Bi_2O_3到α-Bi_2O_3相变过程更为迅速。此外,以光催化降解罗丹明B(RhB)为模型反应,考察了不同晶相的Bi_2O_3光催化活性,结果表明Bi_5O_7NO_3和β-Bi_2O_3材料具有优异的光催化性能,而α-Bi_2O_3具有较低的光催化活性。

Phase Transformation and Photocatalytic Properties of Bi2O3 Prepared Using a Precipitation Method

A Bi(OH)₃ precursor was prepared using a precipitation method using bismuth nitrate as a starting material and ammonia as the precipitation agent. Bi(OH)₃ was then calcined at different temperatures and different time. X-ray diffraction (XRD), Raman spectroscopy, thermogravimetry (TG), scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and UV-Vis diffuse reflectance spectroscopy (UVVis DRS) were used to investigate the phase transformation from Bi(OH)₃ to Bi₂O₃ and the particle size, morphology, and optical properties of Bi₂O₃ during the phase transformation. It was found that Bi(OH)₃ after calcination undergoes the following process: Bi(OH)₃→Bi₅O₇NO₃→β-Bi₂O₃/Bi₅O₇NO₃→β-Bi₂O₃/Bi₅O₇NO₃/α-Bi₂O₃→α-Bi₂O₃. It was observed that the above phase transformation from Bi(OH)₃ to Bi₂O₃ and the growth of the particle size are interrelated. It was also found that the phase transition from β-Bi₂O₃ to α-Bi₂O₃ was faster compared with the phase transition from Bi₅O₇NO₃ to β-Bi₂O₃. Also, the degradation of Rhodamine B (RhB) was studied to investigate and compare the photocatalytic performance of Bi₂O₃ with different crystalline phases. The result indicates that Bi₅O₇NO₃ and β-Bi₂O₃ exhibit excellent photocatalytic performance, while α-Bi₂O₃ has a low photocatalytic activity.