Department of Chemical and Materials Engineering, Pontifical Catholic University of Rio de Janeiro (PUC-Rio), Rio de Janeiro22453-900, Brazil.
Department of Physics, Federal University of Minas Gerais, Belo Horizonte31270-901, Brazil.
Inorg Chem. 2023 Feb 6;62(5):2273-2288. doi: 10.1021/acs.inorgchem.2c04016. Epub 2023 Jan 26.
TiO-based visible-light-sensitive nanomaterials are widely studied for photocatalytic applications under UV-Vis radiation. Among the mechanisms of visible-light sensitization, extrinsic oxygen vacancies have been introduced into TiO and charge-transfer complexes (CTCs) have been formed between chelating ligands, such as acetylacetone, and nanocrystalline TiO (TiO-ACAC). However, the influence of extrinsic oxygen vacancies on the photocatalytic performance of TiO-based CTCs is unknown. In this work, surface/bulk extrinsic oxygen vacancies were introduced into TiO-ACAC through calcination at 270 °C under static air, argon, and hydrogen atmospheres. TiO-ACAC CTCs were characterized by X-ray powder diffraction, thermogravimetric analysis, diffuse-reflectance spectroscopy, photoluminescence, electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy techniques. The correlation between EPR-spin trapping and tetracycline (TC) photodegradation, using scavengers, highlighted the key role of the superoxide radical in TC degradation by TiO-ACAC CTCs under low-power visible-light radiation. The increased extrinsic oxygen vacancies concentration was not beneficial for the photocatalytic performance of TiO CTCs, since bulk extrinsic oxygen vacancies additionally act as recombination centers. In fact, the TiO-ACAC CTC with the lowest extrinsic oxygen vacancies concentration exhibited the highest photocatalytic performance for TC degradation due to an adequate distribution of extrinsic bulk oxygen vacancies, which led to the trapped electrons undergoing repeated hopping, reducing the recombination rates and improving the efficiency in superoxide radicals production. Our findings indicated that TiO-ACAC CTCs are able to degrade pollutants via interactions with electronic holes and principally superoxide radicals and also, provided fundamental information about the influence of surface/bulk extrinsic oxygen vacancies on the photocatalytic performance, lattice parameters, and optical and photochemical properties of TiO-based CTCs.
基于 TiO2 的可见光敏纳米材料因其在紫外-可见辐射下的光催化应用而得到广泛研究。在可见光敏化的机制中，已经将外源性氧空位引入 TiO2 中，并在螯合配体（如乙酰丙酮）和纳米晶 TiO2（TiO-ACAC）之间形成了电荷转移配合物（CTCs）。然而，外源性氧空位对基于 TiO2 的 CTCs 的光催化性能的影响尚不清楚。在这项工作中，通过在静态空气、氩气和氢气气氛下于 270°C 煅烧，将表面/体相外源性氧空位引入 TiO-ACAC 中。通过 X 射线粉末衍射、热重分析、漫反射光谱、光致发光、电子顺磁共振（EPR）和 X 射线光电子能谱技术对 TiO-ACAC CTCs 进行了表征。使用猝灭剂对 EPR 自旋捕获与四环素（TC）光降解之间的相关性进行了研究，突出了超氧自由基在低功率可见光辐射下通过 TiO-ACAC CTCs 降解 TC 的关键作用。外源性氧空位浓度的增加不利于 TiO CTCs 的光催化性能，因为体相外源性氧空位还充当复合中心。事实上，由于外源性体相氧空位的分布均匀，具有最低外源性氧空位浓度的 TiO-ACAC CTC 对 TC 降解表现出最高的光催化性能，这导致被捕获的电子反复跳跃，减少了复合速率并提高了超氧自由基的生成效率。我们的研究结果表明，TiO-ACAC CTCs 能够通过与电子空穴的相互作用主要降解污染物和超氧自由基，同时还提供了有关表面/体相外源性氧空位对基于 TiO2 的 CTCs 的光催化性能、晶格参数以及光学和光化学性质的影响的基本信息。
