pH 值对微波水热合成 BiVO4微晶形貌及光学性能的影响

Influence of pH Value on Morphology and Optical Property of BiVO_4 Crystallites Prepared by Microwave Hydrothermal Process

以NH4VO3和Bi(NO3)3 5H2O为起始原料,在无模板剂的条件下,采用微波水热法可控制备BiVO4微晶。利用X射线衍射仪、扫描电子显微镜和紫外–可见吸收光谱研究了合成溶液的pH值对微波水热合成BiVO4微晶的物相、形貌和光学性能的影响。结果表明:在微波水热条件下,pH值为0.1～10.0,温度为160℃时反应1h,均可制备出单斜相BiVO4微晶,并且随着pH值的增加,产物形貌由片状向棒状转变。pH值越接近中性,(040)晶面衍射峰强度越强,吸收边界越向低波长范围偏移,禁带宽度随之增大。

BiVO4 crystallines with the controllable morphologies were prepared by a template-free microwave hydrothermal method using NH4VO3 and Bi（NO3）3·5H2O as raw materials. The influence of pH value on the phase, morphology and optical property of as-prepared samples was investigated. The samples were characterized by X-ray diffraction, scanning electron microscopy and ultraviolet-visible absorption spectroscopy, respectively. The results indicate that the monoclinic BiVO4 crystalline can be obtained at the pH value of 0.1–10.0, under 160 ℃ for 1 h. The morphology of the crystalline transforms from sheet to rod-like when the pH value increases. When the pH value is close to 7, the diffraction peak intensity of the （040） crystal plane is more intensive, and the optical band gap width also increases. Besides, the corresponding absorbing boundaries are shifted to a lower wavelength range.