目的 针对工业废水中难降解有毒染料污染治理的迫切需求,研发高效光催化水处理技术已成为环境工程领域的研究焦点。基于缺陷工程原理,设计并构筑了氧空位（OVs）可调控的黑色二氧化钛纳米管阵列（B-TNT-x）,旨在强化其光催化降解有机污染物的性能。方法 通过阳极氧化结合铝热还原法调控氧空位浓度,系统研究了氧空位对材料表面特征、晶体与电子结构及光电性能的影响。结果 表征结果表明,成功制备了一系列形貌规整的TiO2纳米管阵列。电子显微学观测表明,OVs主要富集于催化剂表面,并诱导晶格重构,导致催化剂表面粗糙度增加。光电性能测试显示,OVs显著拓宽了催化剂的可见光吸收范围,并提升了电荷转移效率;此外,氧空位修饰赋予催化剂超亲水表面特性,在亚甲基蓝降解实验中,B-TNT-450样品表现出最优性能,降解效率达91.1%。结论 归因于适量OVs通过形成局域缺陷能级缩小了TiO2带隙,同时作为电荷分离中心提升了载流子迁移率,抑制了光生载流子复合,且与超亲水表面结构产生协同效应,进而显著提升了氧空位自掺杂黑色TiO2光催化性能。本研究为缺陷工程调控半导体光催化剂表面功能化及光降解性能提供了理论依据与技术参考。
Abstract
In addressing the urgent need for treatment of refractory toxic dyes in industrial wastewater, the development of efficient photocatalytic water treatment technologies has emerged as a critical focus in environmental engineering. This study demonstrates a novel strategy for constructing oxygen vacancy (OV)-self-doped black TiO2 nanotube arrays (B-TNT-x) via sequential anodization and aluminothermic reduction, aiming to enhance visible-light-driven photocatalytic degradation of organic pollutants. The core innovation resides in the synergistic modulation of OVs to concurrently optimize electronic structure, charge carrier dynamics, and surface wettability, thereby overcoming the inherent limitations of conventional TiO2, including its broadband gap and poor visible-light responsivity.
The fabrication protocol comprises two critical stages: First, well-ordered TiO2 nanotube arrays are constructed via anodic oxidation with a titanium foil as the substrate. Subsequently, the prefabricated TiO2 nanotube arrays (TNT) undergo aluminothermic reduction within an alumina crucible packed with aluminum powder, introducing oxygen vacancies to yield defect-engineered TiO2 nanotube arrays.
Characterization reveals preferential accumulation of oxygen vacancies on the nanotube surface, inducing lattice reconstruction and increased surface roughness. FESEM analysis confirms that the wall thickness of B-TNT-450 reaches 15.33 nm, significantly exceeding that of pristine TNT (10.04 nm). Coupled with quantitative AFM characterization, this roughened surface morphology enhances hydrophilic surface wettability. HRTEM analysis identifies a 2-3 nm amorphous transition layer on B-TNT-450, indicating surface lattice distortion, while XRD confirms OV-induced low-angle shifting of the anatase (101) peak, evidencing lattice expansion attributable to O2- vacancy defects. XPS analysis detecting Ti3+ signatures and oxygen vacancies verifies the successful introduction of OV defects. UV-vis diffuse reflectance spectroscopy demonstrates that B-TNT-x extends light absorption into the visible and near-infrared regions. This phenomenon is ascribed to defect levels within the band gap introduced by oxygen vacancies, which reduce the maximum transition energy of valence electrons, thereby substantially broadening the catalyst's spectral response range. Complementary carrier behavior characterizations further confirm that defect-engineered B-TNT-x exhibits significantly suppressed photogenerated carrier recombination alongside enhanced migration and separation efficiencies. Photocatalytic performance is evaluated under visible-light irradiation. OV modification endows the photocatalyst with superhydrophilic surface properties, facilitating the formation of uniform water films and improving pollutant accessibility to active sites. In degradation experiments with methylene blue (MB) as a model pollutant, B-TNT-450 exhibits optimal performance, achieving 91.1% degradation efficiency with a reaction rate constant k = 0.013 83 min-1 per Langmuir-Hinshelwood kinetics, significantly outperforming unmodified TNT.
Mechanistically, OVs narrow the bandgap, mediating a two-step electron transition from the valence band to defect levels and subsequently to the conduction band, while concurrently functioning as charge separation centers to suppress carrier recombination. Furthermore, oxygen vacancies induce Ti3+ -rich Lewis acid sites, promoting superhydrophilic surface formation and enhancing hydroxyl adsorption capacity. This facilitates more uniform interfacial water film formation, thereby optimizing contact conditions between pollutants and TiO2 surface active sites to augment degradation efficiency. The emergent catalytic enhancement stems from the synergistic optimization of electronic structure and the hydrophilic surface achieved through oxygen vacancy engineering.
This work elucidates the dual regulatory role of oxygen vacancies in modulating electronic properties and surface wettability, establishing an innovative paradigm for defect engineering in photocatalytic materials. The integrated strategy combining structural, electronic, and interfacial modifications establishes a novel pathway for developing high-efficiency visible-light-responsive photocatalysts for advanced wastewater treatment.
关键词
光催化降解 /
氧空位 /
黑色TiO2 /
超亲水性表面 /
表面调控 /
缺陷工程
Key words
photocatalytic degradation /
oxygen vacancies /
black TiO2 /
superhydrophilic surface /
surface modulation /
defect engineering
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基金
山西省基础研究计划项目（202303021212270,202203021212508）
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