RE-B共掺杂片层TiO_2的合成及其光催化性能

采用溶胶-凝胶法,利用钛酸四丁酯、硝酸镧、硝酸铈和硼酸为原料,对TiO_2光催化剂进行稀土-B(RE-B)的共掺杂改性制备和性能研究。采用X-射线衍射法(XRD)、冷场发射扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、紫外-可见吸收(UV-Vis)光谱和荧光(PL)光谱对制得样品的相组成、表面形貌结构、表面元素组成、光响应范围及带隙能和电子-空穴的复合情况进行了初步分析。结果表明,所制掺杂TiO_2的组成均为锐钛矿型,掺杂使晶格发生了较大畸变,且细晶粒由未掺杂的27 nm减小到RE-B-TiO_2的10 nm,形貌为片层状不规则堆放状态存在。XPS结果表明掺杂元素有效进入二氧化钛,PL谱显示共掺杂可有效延长光催化剂的载流子寿命。掺杂后吸收边均红移,La-B-TiO_2由TiO_2的405 nm移动到466 nm,相应地禁带宽度减小了0.4 eV。光催化实验表明:2h内降解亚甲基蓝(MB)时掺杂能够同时提高紫外和可见光下二氧化钛的光催化效率,而共掺杂的降解效果又优于单掺杂,La-B-TiO_2紫外光下的降解率达到80.67%,为同等条件下纯TiO_2的2.7倍,可见光下的降解率为74.78%。

Synthesis and Photocatalytic Activities of Rare Earth-Boron Co-Doped Slice Layer TiO2

Rare earth (RE) and B co-doped (RE-B) nano-TiO₂ photocatalysts were prepared through a sol-gel method using tetrabutyl titanate, lanthanum nitrate, cerous nitrate, and boric acid. The phase constitution, surface morphology, surface elemental compositions, light responsivity, the band gap and the composite of the electronic hole of catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and ultraviolet-visible spectroscopy (UV-Vis). The results show that all the doped products were anatase TiO₂, and RE-B doping generates large lattice distortion and had the function of refining the grain, with the grain size decreasing from 27 nm (TiO₂) to 10 nm (La-B-TiO₂). The doped TiO₂ was flake structure and piled up irregularly. Co-doping enhanced the absorption in the visible region and narrowed the band gap simultaneously. The absorption edge of La-B-TiO₂ moved from 405 nm to 466 nm, and the band gap decreased 0.4 eV correspondingly. XPS results show that the doping elements have effectively doped into the titanium dioxide, and PL spectra show that the co-doping can effectively extend the life of the carrier. The photocatalytic activities of the samples were estimated by degrading methylene blue (MB) under visible and ultraviolet light irradiation for 2 h, and show much improved catalytic activity compared to un-doped TiO₂. The degradation rate of MB using La/B-TiO₂ was 80.67% under ultraviolet light, which is about 2.7 times that of un-doped TiO₂, and 74.78 % under visible light.