可见光下掺N附Ag纳米TiO_2的光催化降解甲基橙

采用溶胶–凝胶法制备纯TiO_2和掺氮TiO_2纳米颗粒(N-TiO_2),然后通过光催化还原在其表面附Ag,得到表面附Ag的纳米TiO_2(即Ag/TiO_2)和掺N附Ag纳米TiO_2(即Ag/N-TiO_2),利用X射线衍射(XRD)、场发射扫描电镜(FE-SEM)、光致发光光谱仪(photoluminescence spectroscopy,PL)、X射线光电子能谱(XPS)以及紫外可见漫反射光谱分析(UV-VIS DRS)对TiO_2及其掺杂改性后的组成和结构、光吸收性能以及可见光下对甲基橙溶液的光催化活性等进行表征。结果表明,所有样品均为锐钛矿型,Ag/TiO_2的平均晶粒度为20.4 nm;N以替代型N-Ti-O、间隙型Ti-O-N(或氧化态Ti-O-N-O)的形式存在于晶格中,银以Ag0形式附着在TiO_2表面;N掺杂抑制TiO_2晶粒的生长,并抑制光生电子与空穴的复合,从而促进TiO_2对可见光的吸收;表面附Ag对TiO_2晶格没有明显影响,但在450~580 nm可见光区产生强烈的表面等离子吸收带并延长至近红外区。TiO_2及其掺杂改性后对甲基橙的光催化效果为Ag/N-TiO_2Ag/TiO_2N-TiO_2TiO_2(或Degussa P25),Ag/N-TiO_2在可见光下对甲基橙(p H=3)进行光催化降解,150 min时降解率达到95%。

Photocatalytic degradation of methyl orange by N-doped and Ag-loaded nano-TiO2 under visible light

N-doped and Ag-loaded nano-TiO2(Ag/N-TiO2), N-doped nano-TiO2(N-TiO2), Ag-loaded nano-TiO2(Ag/TiO2) and pure nano-TiO2(TiO2) were synthesized via sol-gel and photocatalytic reduction route. The as-prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), photoluminescence spectrum (PL), X-ray photoelectron spectroscope (XPS) and UV-visible diffuser reflectance spectroscopy (UV-Vis DRS). The results show that, all samples are pure anatase and the average grain size of Ag/NT is 20.4 nm. N existes in TiO2 lattice in forms of substituted N-Ti-O and interstitial Ti-O-N (or oxidized Ti-O-N-O). Ag is loaded on TiO2 surface in the form of Ag0. N-doping can restrain the growth of grain, prevent the recombination of photoinduced electron and hole, so that it can promote the visible absorbance of TiO2. Ag0 loaded on TiO2 barely affects lattice parameters of TiO2, but significantly results in a strong surface plasmon absorbance band in the visible region of 450?580 nm, which can extend to near infrared region. The degradation rate is in the order of Ag/N-TiO2>Ag/TiO2>N-TiO2>TiO2(or Degussa P25). The degradation rate of methyl orange (MO) can reach 95% after visible light irradiation over Ag/N-TiO2 for 150 min.