Browsing by Author "Zhu, Haiyan"

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C/B codoping effect on band gap narrowing and optical performance of TiO2 photocatalyst: a spin-polarized DFT study
(2013)
Lin, Yanming
;
Jiang, Zhenyi
;
Zhu, Chaoyuan
;
Hu, Xiaoyun
;
Zhang, Xiaodong
The electronic and optical properties of several possible C/B-codoped models of anatase and rutile TiO2 have been investigated systematically using spin-polarized density functional theory calculations. Our calculated results show that the synergistic effect of C/B codoping can induce some hybridized energy states appearing in the forbidden gap and the band gap has a narrowing in anatase and rutile TiO2, which can lead to a decrease of the photon excitation energy and an obvious red-shift of the optical absorption edge. These results lead to an excellent photocatalytic activity in C/B-codoped TiO2. Moreover, with the increase of C and B impurities' concentration in anatase and rutile TiO2, we find that the intensity of impurity states has a strengthening in the band gap, the position of impurity states changes, and the visible-light absorption performance improves gradually.
Electronic and optical performances of Si and Fe-codoped TiO2 nanoparticles: A photocatalyst for the degradation of methylene blue
(2013-10-01)
Lin, Yanming
;
Jiang, Zhenyi
;
Zhu, Chaoyuan
;
Hu, Xiaoyun
;
Zhang, Xiaodong
The effect of substitutional Si, Fe, and Si and Fe (co)doping on the electronic structure and optical properties of anatase and rutile TiO2 have been investigated by the density functional theory. The calculated results indicate that Si doping TiO2 will induce an obvious band gap narrowing by mixing O 2p with Si 3p states, and a series of impurity energy levels (Fe 3d) appear in edge of the VB and the CB through Fe doping. The synergistic effects of Si and Fe codoping can extend optical absorption edge, which leads to higher visible-light photocatalytic activities than pure and monodoped anatase TiO2. Si and Fe-codoped TiO2 nanoparticles was prepared by a sol-gel-solvothermal method, and the photocatalytic activity of TiO2 nanoparticles was examined by measuring the rate of methylene blue decomposition. The experimental results show that Si and Fe-codoped TiO2 sample exhibits better optical absorption performance and higher photocatalytic activities for the degradation of methylene blue than pure and monodoped TiO2, which verifies the reliability of our calculated results. (c) 2013 Elsevier B.V. All rights reserved.
Enhanced optical absorption and photocatalytic activity of anatase TiO2 through (Si,Ni) codoping
(2012-08-06)
Lin, Yanming
;
Jiang, Zhenyi
;
Zhu, Chaoyuan
;
Hu, Xiaoyun
;
Zhang, Xiaodong
The electronic and optical properties of (Si,Ni)-codoped anatase TiO2 are investigated using the density functional theory. The calculated results indicate that the synergistic effects of (Si,Ni) codoping can effectively extend the optical absorption edge, which can lead to higher visible-light photocatalytic activity than pure anatase TiO2. To verify the reliability of our calculated results, nanocrystalline (Si,Ni)-codoped TiO2 is synthesized by a sol-gel-solvothermal method, and experimental results also show that the (Si,Ni)-codoped sample exhibits better absorption performance and higher photocatalytic activities than pure TiO2. 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4745193]
Enhanced optical absorption and photocatalytic H-2 production activity of g-C3N4/TiO2 heterostructure by interfacial coupling: A DFT plus U study
(2017-04-13)
Lin, Yanming
;
Shi, Hailong
;
Jiang, Zhenyi
;
Wang, Guanshi
;
Zhang, Xiaodong
The electronic and optical properties of g-C3N4/TiO2 heterostructure are investigated using spin-polarized DFT+U calculations. The equilibrium spacing (1.94 angstrom) and binding energy (24 meV/angstrom(2)) show that g-C3N4/TiO2 is a van der Waals heterostructure. And the calculated band gap of g-C3N4/TiO2 is significantly reduced compared with TiO2. Therefore, the visible light response of g-C3N4/TiO2 heterostructure is remarkably improved. Besides, the predicted type II band alignment would ensure that the electrons can migrate from g-C3N4 monolayer to anatase TiO2 (101) surface, which leads oxidation and redox reactions can occur on g-C3N4 and TiO2, respectively. Finally, a built-in electric field within the interface region will be set. Above processes can benefit the separation of photoexcited carriers and enhance the hydrogen-evolution activity. In addition, compared with TiO2, g-C3N4/TiO2 with higher conduction band minimum energy can effectively produce higher-energy electrons to reduce hydrogen ions. Moreover, the influence of composite distance and the number of g-C3N4 layers are also investigated systematically. The results indicate that the optical absorption is enhanced over the whole spectrum with the increase of the number of g-C3N4 layers. Similar visible light enhancing is also found when the composite distance is decreased. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
The electronic structure, optical absorption and photocatalytic water splitting of (Fe plus Ni)-codoped TiO2: A DFT + U study
(2017-02-23)
Lin, Yanming
;
Jiang, Zhenyi
;
Zhu, Chaoyuan
;
Zhang, Ruiqin
;
Hu, Xiaoyun
The electronic and optical properties of Fe or/and Ni (co)doped anatase and rutile TiO2 were investigated using the spin-polarized density functional theory. Our calculated results indicate that the synergistic effect of (Fe + Ni) codoping can lead to a band gap narrowing and the hybridized states of Fe 3d and Ni 3d appearing in the forbidden gap, which enhances greatly the optical absorption of TiO2 nanomaterials from the ultraviolet-light to the infrared-light region and reduces the recombination of photogenerated electron hole pairs. In particular, (Fe + Ni) codoping can improve greatly the infrared-light absorption of TiO2 nanomaterials. Furthermore, the researches of electronegativity show that (Fe + Ni)codoped TiO2 system has a stronger redox power for hydrogen generation by photo catalytic water splitting compared with pure, Fe-doped, and Ni-doped TiO2 systems. These results lead to an outstanding solar energy photocatalytic water splitting for hydrogen generation in (Fe + Ni)-codoped TiO2 photocatalyst. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
The optical absorption and hydrogen production by water splitting of (Si,Fe)-codoped anatase TiO2 photocatalyst
(2013-05-01)
Lin, Yanming
;
Jiang, Zhenyi
;
Zhu, Chaoyuan
;
Hu, Xiaoyun
;
Zhu, Haiyan
The electronic and optical properties are studied using the density functional theory in (Si,Fe)-codoped anatase TiO2. The calculated results suggest that the synergistic effects of (Si,Fe) codoping can effectively induce the redshift of optical absorption edge, which leads to higher visible-light photocatalytic activity for hydrogen production by water splitting than pure anatase TiO2. To verify the reliability of our calculated results, nanocrystalline (Si,Fe)-codoped TiO2 is synthesized by a sol-gel-solvothermal method, and excellent absorption performance and photocatalytic activity for hydrogen production by water splitting are observed in our experiments. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
The structure, electronic, and optical properties of (Sm,N)-codoped anatase TiO2 photocatalyst: A density functional study
(2014-01-01)
Lin, Yanming
;
Jiang, Zhenyi
;
Zhang, Ruiqin
;
Zhu, Chaoyuan
;
Hu, Xiaoyun
The geometrical, electronic, and optical properties of Sm-doped, N-doped, and (Sm,N)-codoped anatase TiO2 were successfully calculated and simulated using the spin-polarized density functional theory. The researches of geometrical structures show that (Sm,N) codoping leads to lattice distortion, which reduces the recombination of the photogenerated electron-hole pairs. Moreover, the calculated results indicate that the synergistic effects of (Sm,N) codoping can lead to an obvious band gap narrowing and a N 2p state appearing in the forbidden gap, which leads to a significant redshift of the optical absorption edge and enhances the photocatalytic activity of the (Sm,N)-codoped anatase TiO2. (C) 2013 Elsevier Inc. All rights reserved.