镧离子对氧化铈晶体结构及光催化活性的影响 Effect of Lanthanum Ion on Crystal Structure and Photocatalytic Activity of Cerium Oxide

本文采用水热法制备了不同铈镧比例的稀土氧化物。通过X射线衍射(XRD)，扫描电镜(SEM)、能谱仪(EDX)、紫外可见漫反射光谱仪(UV-vis)以及光催化降解亚甲基蓝实验等进行了分析表征。XRD表明所制备的镧掺杂的稀土氧化物均为立方萤石型结构的氧化铈，在80% La掺杂情况下，仍然具有较强的特征衍射峰。La的掺入使衍射峰向低角度偏移，半峰宽变宽；SEM表明，样品呈现类球形的纳米颗粒，且粒径随着镧含量的增加而减小，EDX证明所得产物纯度高，成分与实验设计一致。紫外可见漫反射光谱表明La3+的掺入使CeO2禁带宽度和紫外吸收强弱呈规律变化。亚甲基蓝光催化实验表明纯氧化铈样品的光降解率最大；而纯氧化镧因为禁带宽度大，只有吸附作用。 Rare earth oxides with different cerium lanthanum ratios were prepared by hydrothermal me-thod. X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDX), UV-Vis diffuse reflectance spectroscopy (UV-vis) and photocatalytic degradation of methylene blue (PDMB) were used to characterize them. XRD results showed that the prepared samples show the ceria crystal structure of fluorite cubic structure. The incorporation of La makes the diffraction peak shift to the low angle, and reduces the grain size. SEM showed that the samples presented spherical nanoparticles, and the particle size decreased with the increase of lanthanum content. EDX analysis showed that the obtained product had high purity and the composition was consistent with the experimental design. The UV-visible diffuse reflectance spectra show that the incorporation of La3+ can change the CeO2 band gap and the UV absorption intensity regularly. PDMB also confirmed that the photocatalytic rate of pure cerium oxide samples was the highest, while the pure lanthanum oxide was only absorbable because of its largest band gap.