Photocatalytic reduction of CO2 by cobalt doped TiO2 and ZnO micro/nanostructured materials
- Authors: Mgolombane, Mvano
- Date: 2020
- Subjects: Nanostructures , Catalysis , Nanotechnology , Chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49171 , vital:41607
- Description: Large emissions of carbon dioxide (CO2) in the atmosphere have caused many harmful effects on humans and the environment. Carbon dioxide is a good source C and is used in a number of applications such as synthesis of fossil fuels. Redox reaction of CO2 and H2O with photocatalysts such as TiO2 and ZnO to produce solar fuels is a promising approach in reducing the environmental impacts of greenhouse gasses. This dissertation describes an in-depth synthesis of four photochemical catalysts and their photocatalytic conversion of CO2 to methanol, thereby addressing the above-mentioned problems by applying synthesised nano-based catalysts. Prior to photocatalytic reduction studies, catalysts such as TiO2, Co-doped TiO2, Co-doped TiO2/rGO, ZnO, Co-doped ZnO and Co-doped ZnO/rGO were synthesized and characterized using various spectroscopic and imaging techniques such as Powder X-Ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Transmission Electron Micrograph (TEM), X-ray Photoelectron Spectroscopy (XPS), Brunner- Emmet- Teller measurement (BET), Thermogravimetry Analysis (TGA) and UV-Vis Diffuse Reflectance Spectroscopy (UV-Vis-DRS). The conversion yield of CO2 to methanol on TiO2, Co-doped TiO2 and Co-doped TiO2/rGO reached 32.3 μmol/gcat, 730 μmol/gcat and 936 μmol/gcat, respectively, after 7 h of irradiation. Theoretical studies via Density functional theory (DFT) revealed that doping TiO2 with Co ions facilitated the formation of adsorbed carbonate or CO2•- species, as CO2 adsorbs onto Co-doped TiO2 surface with binding energy (BE) of -18.12 KJ/mol. The photocatalytic activities of ZnO-based nanomaterials found that Co-doped ZnO/rGO with high ratio of Co, reduced graphene (rGO) and large surface area (10.62 m2g-1) possessed higher CH3OH (30.1 μmol/g) in comparison with Co-doped ZnO (27.3 μmol/g) and ZnO (7.5 μmol/g). The research will deepen the understanding that TiO2 based photocatalyst show higher activity and the mole ratio (Ti/Zn:Co) influences nanocomposites performance and provide new ideas for designing efficient photocatalysts.
- Full Text:
- Date Issued: 2020
- Authors: Mgolombane, Mvano
- Date: 2020
- Subjects: Nanostructures , Catalysis , Nanotechnology , Chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49171 , vital:41607
- Description: Large emissions of carbon dioxide (CO2) in the atmosphere have caused many harmful effects on humans and the environment. Carbon dioxide is a good source C and is used in a number of applications such as synthesis of fossil fuels. Redox reaction of CO2 and H2O with photocatalysts such as TiO2 and ZnO to produce solar fuels is a promising approach in reducing the environmental impacts of greenhouse gasses. This dissertation describes an in-depth synthesis of four photochemical catalysts and their photocatalytic conversion of CO2 to methanol, thereby addressing the above-mentioned problems by applying synthesised nano-based catalysts. Prior to photocatalytic reduction studies, catalysts such as TiO2, Co-doped TiO2, Co-doped TiO2/rGO, ZnO, Co-doped ZnO and Co-doped ZnO/rGO were synthesized and characterized using various spectroscopic and imaging techniques such as Powder X-Ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Transmission Electron Micrograph (TEM), X-ray Photoelectron Spectroscopy (XPS), Brunner- Emmet- Teller measurement (BET), Thermogravimetry Analysis (TGA) and UV-Vis Diffuse Reflectance Spectroscopy (UV-Vis-DRS). The conversion yield of CO2 to methanol on TiO2, Co-doped TiO2 and Co-doped TiO2/rGO reached 32.3 μmol/gcat, 730 μmol/gcat and 936 μmol/gcat, respectively, after 7 h of irradiation. Theoretical studies via Density functional theory (DFT) revealed that doping TiO2 with Co ions facilitated the formation of adsorbed carbonate or CO2•- species, as CO2 adsorbs onto Co-doped TiO2 surface with binding energy (BE) of -18.12 KJ/mol. The photocatalytic activities of ZnO-based nanomaterials found that Co-doped ZnO/rGO with high ratio of Co, reduced graphene (rGO) and large surface area (10.62 m2g-1) possessed higher CH3OH (30.1 μmol/g) in comparison with Co-doped ZnO (27.3 μmol/g) and ZnO (7.5 μmol/g). The research will deepen the understanding that TiO2 based photocatalyst show higher activity and the mole ratio (Ti/Zn:Co) influences nanocomposites performance and provide new ideas for designing efficient photocatalysts.
- Full Text:
- Date Issued: 2020
The political and administrative interface on the local government sphere :|bNelson Mandela Bay Municipality
- Authors: Maqoko, Zandile
- Date: 2015
- Subjects: Local government -- South Africa -- Nelson Mandela Bay Municipality , Politicians -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/5757 , vital:20999
- Description: Municipalities in South Africa are experiencing serious challenges in dealing with the interface between politicians and administrators. The study is based on the political and administrative interface (the relationship between the politicians and administration) in the Nelson Mandela Bay Municipality. An introductory background as well as a theoretical perspective on the phenomenon of ‘politics-administration interface’ and highlights on the significant role that this phenomenon plays in promoting good governance in local government is provided. The study analyses the legislative and policy framework that regulates local government and provides various theoretical models that deal with the political administrative relationships such as the dichotomy model, politicised model and complementarity model. The qualitative research method was used in the study, that is, a secondary data design as a method to collect data, which was supplemented by an extensive literature review. Secondary data sources such as reports, policies, newspapers, books were used to collect data. The descriptive case study and the documentary analysis methods were utilised to investigate the relationship between the politicians and administrators in the municipality. The major challenge in local government is that both politicians and administrators interfere in each other’s roles and responsibilities and this results in major conflict in the municipalities and frustration among the staff because they are not free to undertake their daily functions without interference. The findings reflected that there is a need to professionalise and de-politicised local government. The study makes a number of recommendations which included, inter alia, regulating political interference in administration, clarity of roles and responsibilities of politicians and administrators and separating the municipal administration from politics.
- Full Text:
- Date Issued: 2015
- Authors: Maqoko, Zandile
- Date: 2015
- Subjects: Local government -- South Africa -- Nelson Mandela Bay Municipality , Politicians -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/5757 , vital:20999
- Description: Municipalities in South Africa are experiencing serious challenges in dealing with the interface between politicians and administrators. The study is based on the political and administrative interface (the relationship between the politicians and administration) in the Nelson Mandela Bay Municipality. An introductory background as well as a theoretical perspective on the phenomenon of ‘politics-administration interface’ and highlights on the significant role that this phenomenon plays in promoting good governance in local government is provided. The study analyses the legislative and policy framework that regulates local government and provides various theoretical models that deal with the political administrative relationships such as the dichotomy model, politicised model and complementarity model. The qualitative research method was used in the study, that is, a secondary data design as a method to collect data, which was supplemented by an extensive literature review. Secondary data sources such as reports, policies, newspapers, books were used to collect data. The descriptive case study and the documentary analysis methods were utilised to investigate the relationship between the politicians and administrators in the municipality. The major challenge in local government is that both politicians and administrators interfere in each other’s roles and responsibilities and this results in major conflict in the municipalities and frustration among the staff because they are not free to undertake their daily functions without interference. The findings reflected that there is a need to professionalise and de-politicised local government. The study makes a number of recommendations which included, inter alia, regulating political interference in administration, clarity of roles and responsibilities of politicians and administrators and separating the municipal administration from politics.
- Full Text:
- Date Issued: 2015
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