Theoretical Investigation of Bismuth-Based Semiconductors for Photocatalytic Applications

Handle URI:
http://hdl.handle.net/10754/626307
Title:
Theoretical Investigation of Bismuth-Based Semiconductors for Photocatalytic Applications
Authors:
Laradhi, Shaikhah ( 0000-0001-9061-8397 )
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.
Advisors:
Cavallo, Luigi ( 0000-0002-1398-338X )
Committee Member:
Takanabe, Kazuhiro ( 0000-0001-5374-9451 ) ; Nunes, Suzana Pereira ( 0000-0002-3669-138X ) ; Adi, Fatwa
KAUST Department:
Physical Sciences and Engineering (PSE) Division
Program:
Chemical Sciences
Issue Date:
Nov-2017
Type:
Dissertation
Appears in Collections:
Dissertations

Full metadata record

DC FieldValue Language
dc.contributor.advisorCavallo, Luigien
dc.contributor.authorLaradhi, Shaikhahen
dc.date.accessioned2017-12-07T08:21:37Z-
dc.date.available2017-12-07T08:21:37Z-
dc.date.issued2017-11-
dc.identifier.urihttp://hdl.handle.net/10754/626307-
dc.description.abstractConverting 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.en
dc.language.isoenen
dc.subjectPhotocatalyticen
dc.subjectSemiconductorsen
dc.subjectDFTen
dc.subjectWater Splittingen
dc.subjectOptoelectronicsen
dc.subjectCarrier transporten
dc.titleTheoretical Investigation of Bismuth-Based Semiconductors for Photocatalytic Applicationsen
dc.typeDissertationen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
thesis.degree.grantorKing Abdullah University of Science and Technologyen
dc.contributor.committeememberTakanabe, Kazuhiroen
dc.contributor.committeememberNunes, Suzana Pereiraen
dc.contributor.committeememberAdi, Fatwaen
thesis.degree.disciplineChemical Sciencesen
thesis.degree.nameDoctor of Philosophyen
dc.person.id118458en
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