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    Theoretical Investigation of Bismuth-Based Semiconductors for Photocatalytic Applications

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    Name:
    Sheikha_Dissertation_30112017.pdf
    Size:
    19.73Mb
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    PDF
    Description:
    Shaikhah Lardadhi - Final Dissertation
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    Type
    Dissertation
    Authors
    Lardhi, Sheikha F. cc
    Advisors
    Cavallo, Luigi cc
    Committee members
    Takanabe, Kazuhiro cc
    Nunes, Suzana Pereira cc
    Adi, Fatwa
    Program
    Chemical Science
    KAUST Department
    Physical Science and Engineering (PSE) Division
    Date
    2017-11
    Embargo End Date
    2018-12-07
    Permanent link to this record
    http://hdl.handle.net/10754/626307
    
    Metadata
    Show full item record
    Access Restrictions
    At the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation became available to the public after the expiration of the embargo on 2018-12-07.
    Abstract
    Converting solar energy to clean fuel has gained remarkable attention as an emerged renewable energy resource but optimum efficiency in photocatalytic applications has not yet been reached. One of the dominant factors is designing efficient photocatalytic semiconductors. The research reveals a theoretical investigation of optoelectronic properties of bismuth-based metal oxide and oxysulfide semiconductors using highly accurate first-principles quantum method based on density functional theory along with the range-separated hybrid HSE06 exchange-correlation functional. First, bismuth titanate compounds including Bi12TiO20, Bi4Ti3O12, and Bi2Ti2O7 were studied in a combined experimental and theoretical approach to prove its photocatalytic activity under UV light. They have unique bismuth layered structure, tunable electronic properties, high dielectric constant and low electron and effective masses in one crystallographic direction allowing for good charge separation and carrier diffusion properties. The accuracy of the investigation was determined by the good agreement between experimental and theoretical values. Next, BiVO4 with the highest efficiency for oxygen evolution was investigated. A discrepancy between the experimental and theoretical bandgap was reported and inspired a systematic study of all intrinsic defects of the material and the corresponding effect on the optical and transport properties. A candidate defective structure was proposed for an efficient photocatalytic performance. To overcome the carrier transport limitation, a mild hydrogen treatment was also introduced. Carrier lifetime was enhanced due to a significant reduction of trap-assisted recombination, either via passivation of deep trap states or reduction of trap state density. Finally, an accurate theoretical approach to design a new family of semiconductors with enhanced optoelectronic properties for water splitting was proposed. We simulated the solid solutions Bi1−xRExCuOS (RE = Y, La, Gd and Lu) from pure BiCuOS to pure RECuOS compositions. Starting from the thermodynamic stability of the solid solution, several properties were computed for each system including bandgaps, dielectric constants, effective masses and exciton binding energies. Several compositions with specific organization and density of Bi and RE atoms, were found to be appropriate for water splitting applications. In General, the presented results give further insights to the experimentalists and recommendations for appropriate future application and defect-design of each material.
    Citation
    Lardhi, S. F. (2017). Theoretical Investigation of Bismuth-Based Semiconductors for Photocatalytic Applications. KAUST Research Repository. https://doi.org/10.25781/KAUST-H8DJM
    DOI
    10.25781/KAUST-H8DJM
    ae974a485f413a2113503eed53cd6c53
    10.25781/KAUST-H8DJM
    Scopus Count
    Collections
    Dissertations; Dissertations; Physical Science and Engineering (PSE) Division; Chemical Science Program

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