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Band Structure Modulation And Surface Modification Of Photocatalysts In H2Production From Solar Water Splitting

Posted on:2014-02-07Degree:MasterType:Thesis
Country:ChinaCandidate:J S DaiFull Text:PDF
GTID:2231330395476730Subject:Environmental Engineering
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Concerning the global energy crisis and environmental issues, photocatalysis using semiconductors and solar light has been attracting tremendous attention. Various UV light driven photocatalysts with relatively high quantum efficiency for water splitting have been developed, while effective visible-light-responsive photocatalysts are still limited.In this research, N doping and solid solution were adopted to modulate the band structure of wide gap photocatalysts so as to expand the light absorption to the visible light range. Furthermore, surface modification with Au was used to improve hydrogen production efficiency. Characterization methods such as XRD, SEM-EDX, TEM, HRTEM, XPS, UV-vis-DRS, DFT calculation and CHI electrochemical station were used to monitor the morphology, compositon and structure of the materials. The photocatalytic activities were tested with hydrogen production from water splitting and the machnism were proposed.Incorporation of N in TiO2introduces a new substitution band of N2p above the valance band of O2p. The band gap of N-TiO2is narrowed to2.87eV compared with3.2eV of TiO2. As a result, N-TiO2exhibits hydrogen production rate of2.1μmol/h under visible light irradiation.Deposition of Au nanoparticles on the surface of N-TiO2extends the vilsible light absorption with surface Plasmon resonace (SPR) effect. Hydrogen production rate from photocatalytic water splitting is enhanced to6.6μmol/h, which is attributed to the increase of electron-hole pair generation rate at the surface of N-TiO2by near-field optical enhancement.(AgNbO3)1-x(SrTiO3)x solid solution has been developed between SrTiO3and AgNbO3and the band gap can be modulated between3.19eV and2.71eV.(AgNb03)o.25(SrTiO3)0.75is found to be of the highest photocatalytic activity, which is co-determined by the visible light absorption ability and the CB energy. Based on the characterization results, a mechanism is proposed on the band structure modulation with solid solution. This research is of great importantance in development of new photocatalysts for efficient solar water splitting.
Keywords/Search Tags:Photocatalysis, Hydrogen evolution, Solid solution, Nitrogendoping, Surface modification
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