新型氮氧化钽/氧空位钨酸铋S型异质结纤维用于高效光催化降解抗生素和还原六价铬:产物毒性分析和光催化机理研究

S-Scheme photocatalyst TaON/Bi_(2)WO_(6) nanofibers with oxygen vacancies for efficient abatement of antibiotics and Cr(VI):Intermediate eco-toxicity analysis and mechanistic insights

近年来,环境污染问题严重地威胁着人类的生存和健康.半导体光催化是一种绿色环保的治理环境污染技术,该技术实现大规模应用的关键在于构建高效的光催化剂.TaON因优异的光电性质、稳定的物理化学性质及适合的能带结构等优势,被广泛应用于光催化水裂解和有害污染物降解等领域.但光生载流子快速复合和比表面积小等问题严重制约了其大规模应用.近年来,人们发现构建新型S型异质结能有效促进光生电子和空穴分离,同时充分保存具有强氧化还原能力的电子和空穴,进而有效提升材料的光催化性能.因此,通过构建新型TaON S型异质结光催化材料有f望开发出高效的可见光光催化体系.本文采用静电纺丝-煅烧-氮化工艺制备出由纳米颗粒组成的多孔TaON纳米纤维,然后采用溶剂热法制得一系列富含氧空位的TaON/Bi_(2)WO_(6) S型异质结纤维,并用于可见光照射下光催化降解抗生素和还原Cr^(6+).实验发现,富含氧空位的Bi_(2)WO_(6)二维纳米片均匀生长在TaON纳米纤维上形成了良好的1D/2D核壳结构,此异质结界面结构有利于界面间电荷的分离和传输.当TaON/Bi_(2)WO_(6)质量比为20 wt%时,在可见光下分别照射50,60和50 min,20 mg复合纤维可降解93.2%的四环素溶液(20 mg/L,100 mL,pH=5.2),83.7%的左氧氟沙星溶液(20 mg/L,100 mL,pH 6.7)以及还原95.6%的Cr^(6+)溶液(10 mg/L,100 mL,pH=2.5),其对三种污染物的去除速率分别是纯Bi_(2)WO_(6)的3.8,2和2.9倍,且远高于纯TaON纤维.此外,该复合纤维具有良好的矿化能力及循环稳定性,在实际废水中依然表现出较好的催化降解活性.表征结果表明,复合纤维光催化活性增强是由于TaON与Bi_(2)WO_(6)之间形成了S型的异质结,并富含氧空位;在内电场,能带弯曲和库仑力的协同作用下,实现了强氧化还原能力的电子和空穴的高效分离和保存,有效提升了体系的光催化性能.综上,本文采用缺陷工程结合异质构筑策略有效地提升了体系的光催化活性,为开发高效的光催化体系提供一定的参考.

Enlightened by natural photosynthesis,developing efficient S-scheme heterojunction photocatalysts for deleterious pollutant removal is of prime importance to restore environment.Herein,novel TaON/Bi_(2)WO_(6) S-scheme heterojunction nanofibers were designed and developed by in-situ growing Bi_(2)WO_(6) nanosheets with oxygen vacancies(OVs)on TaON nanofibers.Thanks to the efficiently spatial charge disassociation and preserved great redox power by the unique S-scheme mechanism and OVs,as well as firmly interfacial contact by the core-shell 1D/2D fibrous hetero-structure via the in-situ growth,the optimized TaON/Bi_(2)WO_(6) heterojunction unveils exceptional visible-light photocatalytic property for abatement of tetracycline(TC),levofloxacin(LEV),and Cr(Ⅵ),respectively by 2.8-fold,1.0-fold,and 1.9-fold enhancement compared to the bare Bi_(2)WO_(6),while maintaining satisfactory stability.Furthermore,the systematic photoreaction tests indicate Ta-ON/Bi_(2)WO_(6) has the high practicality in the elimination of pollutants in aquatic environment.The degradation pathway of tetracycline and intermediate eco-toxicity were determined based on HPLC–MS combined with QSAR calculation,and a possible photocatalytic mechanism was elucidated.This work provides a guideline for designing high-performance TaON-based S-scheme photocatalysts with defects for environment protection.