Abstract:

In recent years, rare earth element-modified titanium dioxide (TiO₂) has demonstrated remarkable potential in environmental catalysis. In this study, a series of rare earth element modified RE-B-TiO₂ (RE = Nd, Sm, Eu, Er, Tm) nanocatalysts were prepared by a solvothermal method, and their performance and mechanism of degradation of tetracycline hydrochloride (TCH) under visible light were systematically investigated. Among these catalysts, Er-B-TiO₂ exhibited the highest photocatalytic activity under visible light irradiation. Multiscale characterization techniques (XRD, TEM, XPS) revealed that Er-B-TiO₂ possesses a distinctive self-assembled nanorod architecture composed of bipyramidal nanocrystals with dual crystal-facet exposure. This unique configuration facilitates enhanced spatial separation efficiency of photogenerated charge carriers. Under visible light illumination, Er-B-TiO₂ achieved 93.2% TCH degradation efficiency within 120 min. Mechanistic studies demonstrated that Er³⁺ doping synergistically enhances catalytic performance through three critical pathways: (1) introducing abundant oxygen vacancy defects, (2) effectively suppressing electron-hole recombination, and (3) extending light absorption to the visible spectrum via 4f-orbital-mediated bandgap engineering. Environmental parameter analysis revealed significant regulatory effects of solution pH and specific anions (e.g., Cl^-, \mathrm{S}{\mathrm{O}}_{\mathrm{4}}^{\mathrm{2}-}) on the degradation process. Radical trapping experiments combined with EPR spectroscopy identified superoxide radicals (·{\mathrm{O}}_{\mathrm{2}}^{-}) as the dominant reactive species. HPLC-MS analysis elucidated the TCH degradation pathway, while toxicity assessment confirmed substantial reduction in ecological toxicity of degradation intermediates. This work not only clarifies the intrinsic mechanism of rare earth elements in enhancing TiO₂ photocatalytic activity through band structure modulation, but also provides new insights for designing efficient and stable visible-light-responsive environmental catalysts.

Key words: catalyst, rare-earth, B-TiO₂, oxygen vacancies, free radical, hydrothermal

摘要：

近年来，稀土元素改性二氧化钛（TiO₂）在环境催化领域展现出巨大潜力。采用溶剂热法制备了一系列稀土元素修饰的RE-B-TiO₂（RE：Nd、Sm、Eu、Er、Tm）纳米催化剂，并系统探究了其在可见光下降解盐酸四环素（TCH）的性能与机理。其中Er-B-TiO₂展现出最优的可见光催化性能。多尺度表征技术（XRD、TEM、XPS等）证实，Er-B-TiO₂由具有双晶面暴露特征的双锥体纳米单元自组装形成纳米棒结构，这种独特的晶体构型显著促进了光生载流子的空间分离效率。在可见光照射下，Er-B-TiO₂对TCH的降解效率在120 min内达到93.2%。深入研究表明，Er³⁺掺杂通过以下协同效应显著提升催化性能：（1）引入丰富的氧空位缺陷；（2）有效抑制光生电子-空穴复合；（3）通过4f能级调控将光响应范围扩展至可见光区。系统考察了环境因素对降解效率的影响，发现溶液pH和特定阴离子（如Cl^-、\mathrm{S}{\mathrm{O}}_{\mathrm{4}}^{\mathrm{2}-}）对反应过程具有显著调控作用。结合自由基捕获实验和EPR分析，证实超氧自由基（·{\mathrm{O}}_{\mathrm{2}}^{-}）是降解过程中的主要活性物种。通过高效液相色谱-质谱（HPLC-MS）的分析揭示了TCH的降解路径，毒性评估表明降解中间体的生态毒性显著降低。本研究阐明了稀土元素通过能带工程增强TiO₂光催化活性的内在机制，可为设计高效稳定的可见光响应型环境催化剂提供新思路。

关键词: 催化剂, 稀土, B-TiO₂, 氧空位, 自由基, 水热