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Zhu H.,Chongqing Key Laboratory on Optoelectronic Functional Materials | Feng Q.,Chongqing Normal University | Feng Q.,Chongqing Key Laboratory on Optoelectronic Functional Materials | Yue Y.,Chongqing Key Laboratory on Optoelectronic Functional Materials
Zhongguo Jiguang/Chinese Journal of Lasers | Year: 2014

The change is optical properties and the extention of the application in the field of photocatalysis and photoelectric conversion of the metal and nonmetal-co-doped TiO2 are heatedly studied in recent years. The properties of band structure, density of states, optical properties and defect formation energy of rutile TiO2 super-cell with metallic and nonmetallic impurity co-doped with N-Ru, N-Rh and N-Pd are calculated by plane wave pseudopotential method based on the density functional theory. The results show that rutile TiO2 co-doped with N, N-Ru, N-Rh and N-Pd improve the visible light absorption and utilization efficiency. The defect formation energies decrease in the order of N-Pd, N-Rh and N-Ru, which shows that N-Ru is the most easily doped into TiO2 lattice in co-doped condition. TiO2 co-doped with N-Rh greatly improves absorptivity and reflectivity and achieves the best effect in the range of visible light wavelength. Source


Tian Y.,Chongqing Normal University | Feng Q.,Chongqing Normal University | Feng Q.,Chongqing Key Laboratory on Optoelectronic Functional Materials | Ding S.,Chongqing Normal University | And 3 more authors.
Guangxue Xuebao/Acta Optica Sinica | Year: 2013

Recently, through nonmetallic impurity doping rutile TiO2 to change its optical properties and expand the application in the fields of photocatalysis and photoelectric conversion is a hot research topic. The electronic properties and optical properties of rutile TiO2 super cell with nonmetallic impurity doped (including C, N, S, C-N, C-S, N-S) are calculated by plane wave pseudopotential method based on the density functional theory, such as the band structure, density of states, dielectric constant, absorption spectroscopy and reflection spectroscopy, etc. Nonmetallic elements doping makes TiO2 band gap decrease, and the absorption spectrum and reflection spectra exhibit red shift. To a certain extent, nonmetallic impurity doping improves the TiO2 utilization of visible light, but visible light utilization rate of co-doped TiO2 is higher than that of single-doped TiO2. The research results show that in the visible light high energy area from 400 nm to 575 nm, C-doped rutile TiO2 performs much better than others in absorptivity and reflectivity. In the visible light low energy area from 575 nm to 760 nm, absorptivity and reflectivity of N-doped rutile TiO2 are much better than others. Therefore, the visible light utilization in C-N co-doped TiO2 is better than those of other nonmetallic doped systems. Source


Zhu H.,Chongqing Normal University | Zhu H.,Chongqing Key Laboratory on Optoelectronic Functional Materials | Feng Q.,Chongqing Normal University | Feng Q.,Chongqing Key Laboratory on Optoelectronic Functional Materials
Zhongguo Jiguang/Chinese Journal of Lasers | Year: 2015

Using the first-principles plane-wave ultrasoft pseudopotential method based on density functional theory (DFT) system, the study on titanium dioxide surface adsorption hydrogen halide gas (HX, X=F, Cl, Br) and oxygen vacancy oxidation characteristics is carried out. The calculation results show that: 1) The surface containing oxygen vacancy adsorbed hydrogen halide gas easier, whose adsorption method is chemical adsorption, among them, HF and HCl reduced by surface oxygen vacancy while HBr oxidized by surface oxygen vacancy, and the stable level of adsorption is HF>HBr>HCl; 2) adsorption hydrogen halide gas molecules can improve optical properties including dielectric constant, absorption coefficient and reflectivity of the TiO2 (110) surface, and the order of improvement ability is HF>HBr>HCl. ©, 2015, Science Press. All right reserved. Source


Zhu H.-Q.,Chongqing Key Laboratory on Optoelectronic Functional Materials | Zhu H.-Q.,Chongqing Normal University | Feng Q.,Chongqing Key Laboratory on Optoelectronic Functional Materials | Feng Q.,Chongqing Normal University
Wuli Xuebao/Acta Physica Sinica | Year: 2014

Using the optical gas sensing materials to adsorb gases can cause the changes of the optical properties of materials. This method can be used to measure the gas composition and is a hot topic of current research in the field of gas sensitive sensors. This paper studies the micro-characteristics of rutile TiO2 (110) surface adsorption of CO molecules. By using the first-principles plane-wave ultrasoft pseudopotential method based on the density functional theory (DFT), the adsorption energy, electron density of states, optical properties and charge density of the surface are calculated. Results show that the TiO2 (110) surface terminating in two coordinated O atoms is the most stable surface, and the structure with C-terminal of CO molecules adsorbed on the surface is the most stable. The higher the oxygen vacancy concentration, the more helpful it is to the adsorption of surface CO molecules. This process is exothermic. When the oxygen vacancy concentration is 33%, the adsorption energy can reach 1.319 eV. After adsorption, the structure of the surface tends to be more stable. Oxygen vacancy oxidizing the CO molecule is the essence of the adsorption process, and the charge of a CO molecule is transferred to the material surface. The CO molecules adsorbed on TiO2 (110) surface containing oxygen vacancies can improve its optical properties in visible light range; moreover, the higher the concentration of oxygen vacancy, the more obvious the improvement of absorption, reflection ability and optical gas sensing performance. © 2014 Chinese Physical Society. Source


Zhu H.,Chongqing Normal University | Zhu H.,Chongqing Key Laboratory on Optoelectronic Functional Materials | Feng Q.,Chongqing Normal University | Feng Q.,Chongqing Key Laboratory on Optoelectronic Functional Materials
Guangxue Xuebao/Acta Optica Sinica | Year: 2014

The study on characteristics of optical gas sensing materials after gas adsorption is a hot issue. The microscopic mechanism and optical characteristics of rutile titanium dioxide (110) surface adsorption NH3 molecules are studied. The results show that NH3 molecules are easy to be adsorbed by rutile titanium dioxide (110) surface containing oxygen vacancies. The higher of oxygen vacancy concentration, the more stability of NH3 adsorption, and the main way of surface adsorption NH3 molecule is negative charge center down. When oxygen vacancy concentration reached 33%, adsorption energy is 1.7313 eV. The adsorption of NH3 is chemical adsorption, and the H atom of NH3 is reduced and N atom is oxidized. In visible light range from 1.5 eV to 3.1 eV, the higher concentration of oxygen vacancy, the more obvious improvement of absorption, reflection ability and optical gas sensing performance. Source

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