La-Doped BiOI Microspheres for Efficient Photocatalytic Oxidation of NO under Visible Light Illumination
La-Doped BiOI Microspheres for Efficient Photocatalytic Oxidation of NO under Visible Light Illumination
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La 掺杂 BiOI 微球在可见光照射下高效光催化氧化 NO
DOI：
10.3866/pku.whxb202009100
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Zhongbiao Wu
中科院分区：
文献类型：
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作者：
Qian Li;Jing Hu;Yi Zhou;Haiqiang Wang;Zhongbiao Wu
光催化氧化技术是一种经济有效的低浓度NO处理技术。三维BiOI微球是典型的可见光响应型半导体光催化剂，但在应用于NO光催化氧化反应时，存在光生载流子复合快、电导率不理想等问题。然而，由于它们的微尺寸结构，它们通常难以与其他半导体和助催化剂偶联，因为它们的松散界面提供不充分的接触。采用一步溶剂热法对BiOI微球进行稀土金属（La）掺杂改性，系统研究了其在可见光照射下的光催化NO氧化性能。进一步优化了La的前驱体和掺杂量。结果表明，La（NO3）2是最好的前驱体，而LaCl 3和La（AC）3则是最好的前驱体。此外，0.3%La/BiOI表现出最佳的NO光催化转化效率高达74%，这显著高于纯BiOI基准（44%）。在连续5个循环的实验中，它也表现出优异的稳定性。物理化学性质的分析表明，La掺杂促进BiOI的结晶，而不改变其形态和结构。La 3+可以通过取代Bi 3+或形成La 2 O3纳米团簇均匀分散在BiOI微球的介孔中而进入BiOI晶格。对潜在机制的分析进一步揭示了La掺杂不仅通过降低BiOI的带隙和加速电荷分离和转移动力学来增强光捕获性能，而且通过解离水分子来引入更多的氧空位并促进更多OH自由基的形成。这些因素共同促进了NO的光催化氧化活性。此外，NO在La/BiOI上主要被氧化为NO2，生成的NO2易于从催化剂表面脱附，不仅保持了活性位的完整性，有利于NO光催化氧化反应的持续进行，而且避免了催化剂的频繁洗涤再生，因此La/BiOI具有上级光催化稳定性和长期运行的能力。生成的NO2容易被尾碱液完全吸收，有效避免了二次污染。因此，本研究阐明掺杂确实是一种可行且有效的3D BiOI微球改性方法，同时为各种光催化应用的其他3D半导体材料的合理设计和改性提供灵感。
Photocatalytic oxidation has been widely acknowledged as an economical and effective technology for the treatment of lowconcentration NO. Three-dimensional (3D) BiOI microspheres, which are typical visible-light responsive semiconductor photocatalysts, often suffer from quick recombination of photogenerated carriers and unsatisfactory electrical conductivity when applied in NO photocatalytic oxidation reactions. However, owing to their micro-sized structures, they are usually difficult to couple with other semiconductors and co-catalysts because of their incompact interfaces that provide insufficient contact. In this study, a rare-earth metal (La) doping strategy was first adopted to modify BiOI microspheres via a simple one-step solvothermal method; subsequently, the photocatalytic NO oxidation performance under visible light illumination was systematically investigated. Further, the La precursors and doping contents were optimized. It was found that La(NO3)2 was the best precursor when compared to LaCl3 and La(AC)3. Moreover, 0.3%La/BiOI exhibited the best NO photocatalytic conversion efficiency of up to 74%, which was significantly higher than that of the pure BiOI benchmark (44%). It also exhibited excellent stability during the continuous 5-cycle experiments. Analysis of the physicochemical properties revealed that La doping facilitated the crystallization of BiOI without altering its morphology and structure. La3+ may enter the BiOI lattice by substituting Bi3+ or forming La2O3 nanoclusters that homogeneously scatter in the mesopores of BiOI microspheres. The analysis of the underlying mechanism further revealed that La doping not only enhanced the light harvesting properties by decreasing the bandgaps of BiOI and accelerating the charge separation and transfer dynamics, but also introduced more oxygen vacancies and facilitated the formation of more OH radicals by dissociating the water molecules. All these factors co-contributed to the promotion of NO photocatalytic oxidation activities. Furthermore, NO was mainly oxidized to NO2 over La/BiOI, and the formed NO2 tended to desorb from the catalyst surface, which not only maintained the intactness of active sites and facilitated the sustainable occurrence of NO photocatalytic oxidation reactions, but also prevented the photocatalysts from frequent washing-regeneration; therefore, these factors account for the superior photocatalytic stability of La/BiOI and its long-term operation. The formed NO2 could be easily and totally absorbed by the tail alkaline liquid, thereby effectively avoiding secondary pollution. Therefore, this study elucidates that doping is indeed a feasible and effective approach for the modification of 3D BiOI microspheres, while providing inspiration for the rational design and modification of other 3D semiconductor materials for various photocatalytic applications.