Xin Baifu, Jing Liqiang, Ren Zhiyu, Wang Baiqi, Fu Honggang
Laboratory of Physical Chemistry, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080, China.
J Phys Chem B. 2005 Feb 24;109(7):2805-9. doi: 10.1021/jp0469618.
Ag-TiO2 catalysts with different Ag contents were prepared via a sol-gel method in the absence of light. Based on the characterizations of XRD, photoluminescence (PL), surface photovoltage spectroscopy (SPS), field-induced surface photovoltage spectroscopy (FISPS), and XPS as well as the evaluation of the photocatalytic activity for degrading rhodamine B(RhB) solutions, it was found that the Ag dopant promoted the phase transformation as well as had an inhibition effect on the growth of anatase crystallite. The PL and SPS intensities were decreased with increasing Ag content, indicating that the Ag dopant could effectively inhibit the recombination of the photoinduced electrons and holes. However, the active sites capturing the photoinduced electrons reduced, while the Ag content exceeded 5 mol %. At rather low Ag dopant concentrations, the migration and diffusion of Ag+ ions were predominant, while at rather high Ag dopant concentrations, the migration, diffusion, and reduction of Ag ions simultaneously occurred. The Ag-TiO2 photocatalysts with appropriate content of Ag (Ag species concentration is from about 3 to 5 mol %) possessed abundant electron traps so as to be favorable for the separation of the photoinduced electron-hole pairs, which could greatly enhance the activity of the photocatalysts. From the results of FISPS measurements, it could be found that the impurity bands and abundant surface states were introduced into the interfacial layer of TiO2 because of Ag simultaneously doping and depositing, which could improve the absorption capability for visible light of the photocatalysts.
在无光条件下通过溶胶-凝胶法制备了具有不同银含量的Ag-TiO₂催化剂。基于X射线衍射（XRD）、光致发光（PL）、表面光电压光谱（SPS）、场诱导表面光电压光谱（FISPS）和X射线光电子能谱（XPS）表征以及对罗丹明B（RhB）溶液降解的光催化活性评估，发现银掺杂剂促进了相变，同时对锐钛矿微晶的生长有抑制作用。随着银含量的增加，PL和SPS强度降低，表明银掺杂剂可有效抑制光生电子和空穴的复合。然而，当银含量超过5 mol%时，捕获光生电子的活性位点减少。在较低的银掺杂剂浓度下，Ag⁺离子的迁移和扩散占主导，而在较高的银掺杂剂浓度下，银离子的迁移、扩散和还原同时发生。具有适当银含量（银物种浓度约为3至5 mol%）的Ag-TiO₂光催化剂具有丰富的电子陷阱，有利于光生电子-空穴对的分离，可大大提高光催化剂的活性。从FISPS测量结果可以发现，由于银的同时掺杂和沉积，在TiO₂界面层引入了杂质带和丰富的表面态，这可以提高光催化剂对可见光的吸收能力。
