Browsing by Author "Zhao, Yali"

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Electronic and optical performances of (Cu, N) codoped TiO2/g-C3N4 heterostructure photocatalyst: A spin-polarized DFT plus U study
(2018-03-01)
Zhao, Yali
;
Lin, Yanming
;
Wang, Guanshi
;
Jiang, Zhenyi
;
Zhang, Ruiqin
The geometrical, electronic and optical properties of Cu or/and N (co)doped TiO2/g-C3N4 heterostructure systems have been investigated systematically on the basis of spin-polarized density functional theory calculations. Our calculated results indicate that the band gap of TiO2/g-C3N4 heterostructure has an obvious narrowing compared with pure TiO2 (1 0 1) surface, and (Cu, N) codoping can induce some impurity states of N 2p and hybridized states of Cu 3d and N 2p appearing in the forbidden gap of TiO2/g-C3N4 heterostructure, which lead to a decrease of the photon excitation energy and an obvious redshift of the optical absorption edge. Moreover, the charge density difference calculations of Cu or/and N (co)doped TiO2/g-C3N4 heterostructure systems show that the excited electrons and holes will eventually accumulate in (co)doping TiO2 (1 0 1) surface and g-C3N4 monolayer, respectively, which can effectively reduce the recombination of the photogenerated electron-hole pairs by the interfacial coupling of between TiO2 (1 01) surface and g-C3N4 monolayer. This work not only investigates systematically the electronic and optical properties of Cu or/and N (co)doped TiO2/g-C3N4 heterostructure, but also suggests that (Cu, N) codoped TiO2/g-C3N4 heterostructure is a preferable visible-light photocatalyst.
Enhanced photovoltaic performance of dye-sensitized solar cells by the adsorption of Zn-porphyrin dye molecule on TiO2 surfaces
(2019-07-25)
Lin, Yanming
;
Zhu, Chaoyuan
;
Jiang, Zhenyi
;
Zhao, Yali
;
Wang, Qi
The electronic structure, optical absorption and charge transfer performances of Zn-porphyrin (ZnPP) dye molecule adsorbed on anatase (101) and rutile (110) TiO2 surfaces have been investigated systematically using spin-polarized density functional theory calculations. The calculated results indicate that the strong interactions of ZnPP dye molecule and TiO2 surfaces cause an obvious variation of the conduction band minimum and valence band maximum for ZnPP dye molecule adsorbed on TiO2 surfaces, and the valence band of adsorption systems has a large bandwidth compared with that of the TiO2 bulk and surfaces, which induces a red-shift of the optical absorption edge and improves greatly the optical absorption of adsorption systems in the ultraviolet and visible light regions. Moreover, the change of charge density indicates that the photoelectrons transfer from the ZnPP dye molecule to TiO2 across the interface, and a built-in electric field is formed at the interface, which effectively enhances the separation of photogenerated electron-hole pairs. These results suggest that the sensitized actions of ZnPP dye molecule on TiO2 surfaces can generate an excellent photovoltaic performance of TiO2 photoanode in DSSCs. (c) 2019 Elsevier B.V. All rights reserved.
Photocatalytic water splitting of (F, Ti) codoped heptazine/triazine based g-C3N4 heterostructure: A hybrid DFT study
(2019-01-01)
Zhao, Yali
;
Lin, Yanming
;
Wang, Guanshi
;
Jiang, Zhenyi
;
Zhang, Ruiqin
Graphitic carbon nitride (g-C3N4) has been widely investigated as a metal-free photocatalyst for water splitting. However, the rapid recombination of photoexcited carriers and narrow visible-light response region substantially limit its performance. In this work, we have systematically studied the geometrical, electronic, optical, charge transfer and photocatalytic mechanism of (F, Ti) codoped heptazine/triazine based g-C3N4 heterostructure using hybrid density functional approach. The interface interaction between heptazine and triazine gC(3)N(4) shows heptazine and triazine g-C3N4 form a Van Der Waals heterostructure. The bandgap of (F, Ti) codoped heptazine/triazine based g-C3N4 heterostructure is narrow (2.39 eV), which enhances the absorption of visible light and leads to an obvious redshift of absorption edge. A type-II heterostructure is formed at the interface of (F, Ti) codoped heptazine/triazine based g-C3N4 heterostructure, and leads to high photocatalytic activity. Furthermore, Bader charge and charge density difference indicate that the internal electric field promotes the separation of electron-hole pairs in the heptazine/triazine g-C3N4 interface and inhibits carrier recombination. Meanwhile, electrons in the conduction band of triazine g-C3N4 and holes in the valence band of (F, Ti) codoped heptazine g-C3N4 have enough redox ability. This work is helpful in understanding the mechanism of photocatalytic water splitting and relevant experimental observations.