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First-principles Calculation on Photocatalytic Performance of TiO2

Author: YiDan
Tutor: XueWeiDong
School: Sichuan Normal University
Course: Materials Science
Keywords: Density functional theory TiO2 mixed phase nano-TiO2 photocatalytic performance Tris (8- hydroxyquinoline -5- carboxylic acid) iron(Ⅲ) Sensitized mechanism
CLC: O614.411
Type: Master's thesis
Year: 2010
Downloads: 166
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Abstract


Based on ultrasoft pseduopotentia plane wave method, the photocatalytic performance of Rutile/Anatase TiO2 mixed crystal was evaluated by first principle calculation. The photo adsorption capacity, the separation efficiency of photo-induced electron-hole pair and the transfer probability of charge carrier were all investigated. The results showed that the separation efficiency of electron-hole pair for mixed TiO2 was clearly higher than single phase TiO2 （ Rutile or Anatase）, and the red-shifting of adsorption peaks was observed notably, which confirmed that the photocatalytic performance of mixed crystal nano-TiO2 is superior to the single phase TiO2.Density functional theory （DFT） in periodic DMol3 program was employed to investigate the sensitization mechanism and electronic structural of tris （ 8- hydroxyquinoline -5- carboxylic acid） iron （Ⅲ）, tris （8- hydroxyquinoline -7- carboxylic acid） iron（Ⅲ） and tris （ 8- hydroxyquinoline -5- sulfonic acid） iron（Ⅲ） on TiO2 anatase （101） surface. These sensitizers possesses a very small HOMO （the highest occupied molecular orbital）- LUMO（the lowest unoccupied molecular orbital） energy gap, and this allows for easy electron excitation from HOMO to the LUMO. As the nanocrystalline TiO2 adsorbs the sensitizer, the energy of the HOMO level, the LUMO and Fermi level increase, These changes lead to an enhancement of the open-circuit photovoltage （VOC） in dye-sensitized TiO2 solar cells.In addition, we theoretically determined the sensitization mechanis+m of tris （8- hydroxyquinoline -5- carboxylic acid） iron （Ⅲ） and tris （8- hydroxyquinoline -7- carboxylic acid） iron（Ⅲ） dyes that are attached by carboxylic acid anchor groups to TiO2 anatase （101） surface; But tris （ 8- hydroxyquinoline -5- sulfonic acid） iron（Ⅲ） dyes are attached by sulfonic acid anchor groups to TiO2 anatase （101） surface. The Energy gap of tris （8- hydroxyquinoline -7- carboxylic acid） iron（Ⅲ） dyes is larger than the other two sensitizers, and can match the ELUMO level of TiO2 very well. tris （8- hydroxyquinoline -7- carboxylic acid） iron（Ⅲ） adsorption more negatively shifted the Fermi level than the other sensitizers adsorption, which corresponded to the enhancement of the Voc values. Consequently, the molecular adsorption of tris （8- hydroxyquinoline -7- carboxylic acid） iron（Ⅲ） is energetically more favoured than those of the other adsorbed molecules.

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CLC: > Mathematical sciences and chemical > Chemistry > Inorganic Chemistry > Metal elements and their compounds > Section Ⅳ group metal elements and their compounds > The titanium Vice family ( IV B group metal elements) > Ti Ti
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