Abstract

In this work, a series of TiO₂ nanostructures doped with well-selected transition metals (Cr, Fe, Co and Zr) was prepared using a simple “one-pot” sol-gel process, followed by a drying under supercritical conditions of solvent. Herein, we carefully highlighted the effect of doping with ions exhibiting higher size than that of Ti⁴⁺ host ion, on physicochemical properties of TiO₂ aerogel nanomaterials, and its photocatalytic behavior in the methylene blue degradation under solar light irradiation. Textural properties revealed materials with high surface areas given by supercritical drying process. TEM analysis of pristine oxide showed quantum-sized, well-dispersed and highly ordered particles. XRD analysis evidenced an increase in anatase lattice volume after doping. A reduction in gap energy can be seen for Cr, Fe and Co doped TiO₂ samples, which is related to the involvement of intermediate energy levels related to dopant ions. Photocatalytic activity of TiO₂ solid shows an apparent improvement when doped with zirconium compared to other doped TiO₂ materials and pristine oxide, which may be mainly correlated to the increase in the amount of oxygen defects given its larger size as shown by PL spectroscopy. Oxygen vacancies act as electron traps thus provide a charge separation enhancing the photoactivity. The low photoactivity of Cr–TiO₂, Fe–TiO₂, and Co–TiO₂ materials was mainly related to the dopant energy levels appearing as charge recombination centers, which can negatively affect the catalytic efficiency. Hence, the efficiency of photocatalysis seems determined by the competition between these two process; charge separation and charge recombination.

中文翻译：

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用于光催化染料脱色的掺杂二氧化钛纳米结构的一锅溶胶-凝胶合成

摘要

在这项工作中，使用简单的“一锅法”溶胶-凝胶工艺制备了一系列掺杂精选过渡金属（Cr、Fe、Co 和 Zr）的 TiO ₂纳米结构，然后在溶剂的超临界条件下干燥. 在此，我们仔细强调了掺杂比 Ti ^{4+主体离子尺寸更大的离子对 TiO} ₂的物理化学性质的影响。气凝胶纳米材料及其在太阳光照射下降解亚甲基蓝的光催化行为。质地特性揭示了由超临界干燥工艺提供的具有高表面积的材料。原始氧化物的 TEM 分析显示出量子大小、分散良好且高度有序的颗粒。XRD分析证明掺杂后锐钛矿晶格体积增加。_{对于 Cr、Fe 和 Co 掺杂的 TiO 2}样品，可以看到间隙能量的降低，这与与掺杂剂离子相关的中间能级的参与有关。_{与其他掺杂的 TiO 2}相比，掺杂锆的 TiO ₂固体的光催化活性显示出明显的提高材料和原始氧化物，这可能主要与氧缺陷量的增加有关，因为它的尺寸较大，如 PL 光谱所示。氧空位充当电子陷阱，因此提供电荷分离以增强光活性。Cr-TiO ₂、Fe-TiO ₂和 Co-TiO ₂材料的低光活性主要与作为电荷复合中心出现的掺杂剂能级有关，这会对催化效率产生负面影响。因此，光催化的效率似乎取决于这两个过程之间的竞争。电荷分离和电荷复合。