氮、硫共掺TiO_2光催化剂的响应曲面法优化

利用响应曲面法(RSM)对溶胶-凝胶法合成N、S共掺TiO2光催化剂(N/S-TiO2)的合成工艺进行了优化,借助XRD、XPS、TEM、UV-Vis-DRS等测试手段对样品进行表征,并以甲基橙为模型污染物考察了样品的可见光催化活性。根据实验结果建立了N、S共掺TiO2降解甲基橙溶液的二次多项式数学模型,并确定N、S共掺TiO2光催化剂的最佳合成工艺为:热处理温度550℃,N和S掺杂量分别为1.0%和0.3%(原子分数),在该条件下所得N/S-TiO2具有较好的可见光催化活性,且对甲基橙溶液的实际降解率与模型预测基本一致,相对误差为4.69%。

One-pot topotactic synthesis of Ti^(3+) self-doped 3D TiO_2 hollow nanoboxes with enhanced visible light response

Ti^（3＋） self-doped anatase three-dimensional（3D） TiO_2 hollow nanoboxes were synthesized via a topological transformation process involving template participation by a facile one-pot hydrothermal treatment with an ethanol solution of zinc powder and TiOF_2. It is worth noting that the 3D TiO_2 hollow nanoboxes are assembled from six single-crystal nanosheets and have dominant exposure of the {001} facets. It is found from EPR spectra that adding zinc powder is an environment-friendly and effective strategy to introduce Ti^（3＋） and oxygen vacancy（Ov） into the bulk of 3D hollow nanoboxes rather than the surface, which is responsible for their enhanced visible photocatalytic properties.The photocatalytic activity was evaluated by measuring the formation rate of hydroxide free radicals using 7-hydroxycoumarin as a probe. The sample prepared with zinc/TiOF_2 mass ratio of0.25 exhibited the highest RhB photodegradation activity under visible-light irradiation with a degradation rate of 96%, which is 4.0-times higher than that of pure TiO_2. The results suggest a novel approach to construct in-situ 3D hierarchical TiO_2 hollow nanoboxes doped with Ti^（3＋） and Ov without introducing any impurity elements for superior visible-light photocatalytic activity.

Thermostable Nitrogen-Doped HTiNbO5 Nanosheets with a High Visible-Light Photocatalytic Activity

Nitrogen-doped HTiNbO5 nanosheets have been successfully synthesized by first exfoliating layered HTiNbO5 in tetrabutylammonium hydroxide （TBAOH） to obtain HTiNbO5 nanosheets and then heating the nanosheets with urea. The resulting samples were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, energy-dispersive X-ray （EDX）, X-ray photoelectron spectroscopy （XPS）, UV-vis spectroscopy and N2 adsorption-desorption measurements. It was found that N-doping resulted in a much higher thermostability of the layered structure, intrinsic bandgap narrowing and a visible light response. The doped nitrogen atoms were mainly located in the interstitial sites of TiNbOs- lamellae and chemically bound to hydrogen ions. Compared with N-doped HTiNbOs, N-doped HTiNbO5 nanosheets had a much larger specific surface area and richer mesoporosity due to fee rather loose and irregular arrangement of fitanoniobate nanosheets. Both N-doped layered HTiNbOs and HTiNbO5 nanosheets showed a very high visible-light photocatalytic activity for the degradation of rhodamine B （RhB） aqueous solution. Moreover, due to the considerably larger surface area, richer mesoporosity and stronger acidity, N-doped HTiNbO5 nanosheets had an even higher activity than N-doped HTiNbOs, although the latter had a stronger absorption in the visible region. The dye molecules were mainly degraded to aliphatic organic compounds and partially mineralized to CO2 and/or CO, rather than being simply decolorized. The effect of photosensitization was insignificant and RhB was degraded mainly via the typical photocatalytic reaction routes. Two different reaction routes for the photodegradation of RhB under visible light irradiation over N-doped HTiNbO5 nanosheets have been proposed. The present method can be extended to a large number of layered metal oxides that have the characteristics of intercalation and exfoliation, thus providing new opportunities for the fabrication of highly effective and potentially practical visible-light photocatalysts.