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Prospective aspects of preferential {001} facets of N,S-co-doped TiO2 photocatalysts for visible-light-responsive photocatalytic activity

机译：N，S-掺杂TiO2光催化剂的优先{001}小平面的前瞻性方面，用于可见光响应光催化活性

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In this report, we describe the synthesis of nitrogen and sulfur co-doped TiO2 photocatalysts (NST) with preferential {001} facets by surfactant-and template-free OPM routes and crystallized through hydrothermal treatment. The precursor solution formed a coordination complex containing Ti-peroxo complex and chelating ligands (thiourea and urea were used as ligands for sulfur and nitrogen-donating sources, respectively). The effects of dopant concentration on the structural and morphological properties of the as-prepared NST photocatalysts were studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), N-2-adsorption-desorption isotherms and defuse reflectance spectroscopy (DRS). The visible-light-driven photocatalytic activity of the as-prepared NST samples was tested for the photodegradation of organic compounds (i.e. rhodamine B and phenol). High-performance liquid chromatography (HPLC) and LC-MS spectroscopy were used to analyze the by-products from the photodegradation of RhB. Different scavengers were added to the photocatalysis system in order to identify the role of active species in the photodegradation of organic compounds on the surface of NST photocatalysts. It was found that hydroxyl radicals (cOH) and photogenerated holes (h(+)) played an important role in the photodegradation of organic compounds under visible-light irradiation. The electronic and structural characterizations of the as-prepared NST samples proved the successful incorporation of dopant elements (i.e. N and S) into the crystal lattice of TiO2-which shifted the absorption edge shoulder from UV to the visible-light region, due to the bandgap transition. Another reason for the red shift of the absorption edge in the visible-light region is expected to be the formation of new energy levels near to the conduction bands, because of the incorporation of dopant elements (N and S) into the bandgap of the TiO2 crystal lattice. More interestingly, the pristine NST-0 sample showed photocatalytic activity, expected to be due to the formation of a substrate-surface complexation, resulting in an absorption shift of TiO2 into the visible light region due to the transfer of charges from the ligand (i.e. the attached dye molecule) to the titanium atoms. Moreover, the photocatalytic efficiency of the as-prepared NST samples was higher than those of the other samples. The prominent synergetic factors responsible for enhanced photocatalytic activity of doped NST samples include: (1) the presence of preferential exposed {001} facets of the anatase TiO2 nanorods, and (2) the introduction of the shift in the absorption edge shoulder towards the visiblelight region. The preferential {001} facets act as a reservoir for the photogenerated charge carriers (i.e. electron-hole pairs) and slow down their rate of recombination. The introduction of absorption shift facilitates the adsorption of organic compounds on the photocatalyst surface.
机译：在本报告中，我们描述了用表面活性剂和模板OPM途径的优先{001}小件合成氮和硫和硫二掺杂TiO2光催化剂（NST），并通过水热处理结晶。前体溶液形成了含有Ti-Peroxo复合物的配位络合物，分别螯合配体（硫脲和尿素作为配体分别用于硫和氮化源的配体）。使用X射线衍射（XRD），X射线光电子电子显微镜（FE-SEM），高位研究掺杂剂浓度对由X射线衍射（XRD），X射线光电子电子显微镜（FE-SEM），高 - Resolution透射电子显微镜（HR-TEM），N-2吸附 - 解吸等温线和沉默反射光谱（DRS）。测试AS制备的NST样品的可见光光催化活性用于有机化合物的光降解（即Rhodamine B和苯酚）。高效液相色谱（HPLC）和LC-MS光谱分析用于分析RHB的光降解的副产物。将不同的清除剂加入到光催化系统中，以识别活性物种在NST光催化剂表面上有机化合物的光降解中的作用。发现羟基自由基（COH）和光生孔（H（+））在可见光照射下的有机化合物的光降解中起重要作用。由制备的MST样品的电子和结构表征证明了将掺杂剂元素（即N和S）的成功掺入TiO 2的晶格 - 这将吸收边缘肩部从UV移至可见光区域，由于带隙转变。预计可见光区域中吸收边缘的红色移位的另一个原因是将新能级的形成，因为掺杂剂元素（n和s）掺入TiO 2的带隙中水晶格子。更有趣的是，原始的NST-0样品显示出光催化活性，预期是由于形成基材表面络合的形成，导致TiO 2的吸收移入可见光区域，由于来自配体的电荷的转移（即附着的染料分子到钛原子。此外，所制备的NST样品的光催化效率高于其他样品的光催化效率。负责增强掺杂NST样品的光催化活性的突出协同因素包括：（1）anaatase TiO2纳米棒的优先暴露的{001}刻面，以及（2）引入吸收边缘肩部朝向visiblelight的转变地区。优选的{001}小平面用作光发化电荷载体的储存器（即电子孔对）并减慢其重组速率。吸收移位的引入有助于在光催化剂表面上吸附有机化合物。

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  • 来源
    《RSC Advances》 |2016年第92期|共14页
  • 作者

    Abu Bakar Shahzad; Ribeiro Caue;

  • 作者单位

    Univ Fed Sao Carlos Dept Chem Rod Washington Luiz Km 235 BR-13565905 Sao Carlos SP Brazil;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 化学;
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