Synthesis and characterization of binary and ternary palladium alloys for use as alternative counter electrode catalysts in dye sensitized solar cells
- Authors: Zingwe, Nyengerai Hillary
- Date: 2020
- Subjects: Electrocatalysis Chemistry
- Language: English
- Type: Thesis , Doctoral , PhD (Chemistry)
- Identifier: http://hdl.handle.net/10353/18513 , vital:42580
- Description: The dye sensitized solar cell counter electrode facilitates the regeneration of the dye molecules thereby ensuring the provision of higher sunlight to electricity conversion efficiency. The standard platinum electrode suffers from low efficiency due to corrosion by the redox mediator as well as being extremely expensive due to high demand. As an alternative this research study illustrates the efforts undertaken to replace the standard platinum counter electrode with palladium alloy counter electrodes. Application of palladium alloys ensures sustenance of high catalytic activity by palladium which is as effective as platinum. Although palladium is equally as expensive as platinum, its application in the form of alloys minimizes the amount required to produce an effective counter electrode to 0.001-0.004 moles thereby ensuring the provision of high efficiency at a lower cost. Furthermore, charge transfer from the other alloyed elements to the palladium atom increases active sites leading to higher catalytic activity than platinum. Additionally, changes in crystal structure due to alloying enhances resistance to corrosion thus enabling the longevity of the alloy counter electrode in the electrolyte ___________________________________________________________________________ Electrochemical analysis was conducted to determine the catalytic functionality of the developed alloys in cobalt, ferrocene and iodine redox mediators. The binary (PdNi-reduced graphene oxide (rGO) and PdCo-rGO) and ternary (PdNiCo-rGO) palladium alloys were fabricated via a hydrothermal method. In order to determine the composition which could provide the maximum activity, optimization was conducted through variation of the molar ratios of the precursor solutions. The properties of the synthesized palladium alloys were determined using various techniques including x-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The developed alloys were observed to comprise of palladium, nickel, cobalt, and carbon atoms. The particles were spherical in nature for all the unsupported alloys with the carbon supported alloys exhibiting spherical particle wholly surrounded by graphene sheets. Cyclic voltammetry and electrochemical impedance spectroscopy analysis showed that the carbon supported alloys PdNi-rGO, PdCo-rGO and PdNiCo-rGO produced the highest catalytic activities due to the synergy between their respective alloys and the incorporated reduced graphene oxide. The high catalytic effectiveness of these alloys yielded power conversion efficiency in the order PdNiCo-rGO (9.01) > PdNi-rGO (8.4.%) > PdCo-rGO (6.56%) > Pt (5.7%) which were better than the platinum efficiency in the cobalt redox mediator. The higher efficiency in the cobalt redox mediator relative to the iodine electrolyte illustrates that they are viable alternatives to the, corrosive and volatile iodine. Obtained results show that, the high recombination rates between the photogenerated electrons and the oxidized dye molecule which have been reported to reduce power conversion efficiency in one electron redox mediators did not affect the performance of the cell. However, these higher recombination rates affected the ferrocene electrolyte leading to extremely poor efficiency metrics. The obtained results indicated that reduced graphene oxide supported PdNi-rGO, PdNiCo-rGO as well as the unsupported PdNi3 alloys could successfully be implemented as substitutes to the platinum counter electrode in dye sensitized solar cells. The application of the palladium alloys is vital for improving stability and power conversion efficiency, as well as reducing cost.
- Full Text:
- Authors: Zingwe, Nyengerai Hillary
- Date: 2020
- Subjects: Electrocatalysis Chemistry
- Language: English
- Type: Thesis , Doctoral , PhD (Chemistry)
- Identifier: http://hdl.handle.net/10353/18513 , vital:42580
- Description: The dye sensitized solar cell counter electrode facilitates the regeneration of the dye molecules thereby ensuring the provision of higher sunlight to electricity conversion efficiency. The standard platinum electrode suffers from low efficiency due to corrosion by the redox mediator as well as being extremely expensive due to high demand. As an alternative this research study illustrates the efforts undertaken to replace the standard platinum counter electrode with palladium alloy counter electrodes. Application of palladium alloys ensures sustenance of high catalytic activity by palladium which is as effective as platinum. Although palladium is equally as expensive as platinum, its application in the form of alloys minimizes the amount required to produce an effective counter electrode to 0.001-0.004 moles thereby ensuring the provision of high efficiency at a lower cost. Furthermore, charge transfer from the other alloyed elements to the palladium atom increases active sites leading to higher catalytic activity than platinum. Additionally, changes in crystal structure due to alloying enhances resistance to corrosion thus enabling the longevity of the alloy counter electrode in the electrolyte ___________________________________________________________________________ Electrochemical analysis was conducted to determine the catalytic functionality of the developed alloys in cobalt, ferrocene and iodine redox mediators. The binary (PdNi-reduced graphene oxide (rGO) and PdCo-rGO) and ternary (PdNiCo-rGO) palladium alloys were fabricated via a hydrothermal method. In order to determine the composition which could provide the maximum activity, optimization was conducted through variation of the molar ratios of the precursor solutions. The properties of the synthesized palladium alloys were determined using various techniques including x-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The developed alloys were observed to comprise of palladium, nickel, cobalt, and carbon atoms. The particles were spherical in nature for all the unsupported alloys with the carbon supported alloys exhibiting spherical particle wholly surrounded by graphene sheets. Cyclic voltammetry and electrochemical impedance spectroscopy analysis showed that the carbon supported alloys PdNi-rGO, PdCo-rGO and PdNiCo-rGO produced the highest catalytic activities due to the synergy between their respective alloys and the incorporated reduced graphene oxide. The high catalytic effectiveness of these alloys yielded power conversion efficiency in the order PdNiCo-rGO (9.01) > PdNi-rGO (8.4.%) > PdCo-rGO (6.56%) > Pt (5.7%) which were better than the platinum efficiency in the cobalt redox mediator. The higher efficiency in the cobalt redox mediator relative to the iodine electrolyte illustrates that they are viable alternatives to the, corrosive and volatile iodine. Obtained results show that, the high recombination rates between the photogenerated electrons and the oxidized dye molecule which have been reported to reduce power conversion efficiency in one electron redox mediators did not affect the performance of the cell. However, these higher recombination rates affected the ferrocene electrolyte leading to extremely poor efficiency metrics. The obtained results indicated that reduced graphene oxide supported PdNi-rGO, PdNiCo-rGO as well as the unsupported PdNi3 alloys could successfully be implemented as substitutes to the platinum counter electrode in dye sensitized solar cells. The application of the palladium alloys is vital for improving stability and power conversion efficiency, as well as reducing cost.
- Full Text:
Application of health belief model in developing contextual guidelines for adherence to antiretroviral treatment among adolescents and youths in Buffalo City Metropolitan Municipality District, East London, South Africa
- Authors: Mayeye, Bulelwa
- Date: 2018
- Subjects: HIV-positive children--Treatment--Management AIDS (Disease) in adolescence HIV-positive youth
- Language: English
- Type: Thesis , Doctoral , Nursing
- Identifier: http://hdl.handle.net/10353/15572 , vital:40472
- Description: Background: Adhering to the treatment instructions for a long-term illness poses a great challenge to the client especially adolescents and youths. In public health centers it is observed that most adolescents and youths on Ante Retroviral Treatment (ART) do not continue taking ART and do not honor their Art related scheduled appointments at the clinic. An increase loss to follow up among these cohorts is noticeable in Buffalo City Metropolitan Municipality district. Inconsistent adherence to ART may result in the development of resistance mutations. Purpose: The purpose of the study was to develop and describe context – specific antiretroviral treatment guidelines based on the biomedical, cognitive and psychosocial needs of the adolescents and youths at the Buffalo City Metropolitan Municipality district. Methodology: The study was conducted in two phases, phase one consisted of quantitative and qualitative approaches. For phase one an explanatory sequential mixed method of quantitative and qualitative designs was employed. The study was guided by Health Belief Model. The target population were adolescents and youths receiving ART from the selected health facilities in Buffalo City Metropolitan Municipality District in the Province of the Eastern Cape. Participants were chosen based on purposive sampling. A convenience sample of 206 adolescents and youths between the ages of 14 to 24 attending ARV clinics were approached. Ethical considerations, that is, the rights of all the participants were honoured. Data was collected using self administered questionnaires followed by semi-structured interview where face to face interviews were conducted. Reliability validity and trustworthiness of the research was ensured. Quantitative data was analysed through descriptive statistics. For qualitative approach transcrips were coded thematically. In Phase 2, context – specific antiretroviral treatment guidelines were developed to promote adherence to ART by adolescents and youths of Buffalo City Metropolitan Municipality district. Results: About 35percent of the participants indicated low adherence, 31percent for moderate adherence and 34percent for high adherence. A strong correlation between interpersonal relationship and adherence (p = 0.008), a correlation between aspect of care related to clinic and adherence (p = 0.028), a significant correlation between social support and adherence to ART (p = 0.006) and a significant relationship between self- efficacy and adherence to ART (p = 0.000) were obtained. No correlation between demographic status and adherence except for race. Results from the interviews revealed that barriers to adherence were more evident than enabling factors. Recommendations: Health service providers should strengthen ART adherence programmes for adolescents and youths by applying principles as they appear in the context – based guidelines.
- Full Text:
- Authors: Mayeye, Bulelwa
- Date: 2018
- Subjects: HIV-positive children--Treatment--Management AIDS (Disease) in adolescence HIV-positive youth
- Language: English
- Type: Thesis , Doctoral , Nursing
- Identifier: http://hdl.handle.net/10353/15572 , vital:40472
- Description: Background: Adhering to the treatment instructions for a long-term illness poses a great challenge to the client especially adolescents and youths. In public health centers it is observed that most adolescents and youths on Ante Retroviral Treatment (ART) do not continue taking ART and do not honor their Art related scheduled appointments at the clinic. An increase loss to follow up among these cohorts is noticeable in Buffalo City Metropolitan Municipality district. Inconsistent adherence to ART may result in the development of resistance mutations. Purpose: The purpose of the study was to develop and describe context – specific antiretroviral treatment guidelines based on the biomedical, cognitive and psychosocial needs of the adolescents and youths at the Buffalo City Metropolitan Municipality district. Methodology: The study was conducted in two phases, phase one consisted of quantitative and qualitative approaches. For phase one an explanatory sequential mixed method of quantitative and qualitative designs was employed. The study was guided by Health Belief Model. The target population were adolescents and youths receiving ART from the selected health facilities in Buffalo City Metropolitan Municipality District in the Province of the Eastern Cape. Participants were chosen based on purposive sampling. A convenience sample of 206 adolescents and youths between the ages of 14 to 24 attending ARV clinics were approached. Ethical considerations, that is, the rights of all the participants were honoured. Data was collected using self administered questionnaires followed by semi-structured interview where face to face interviews were conducted. Reliability validity and trustworthiness of the research was ensured. Quantitative data was analysed through descriptive statistics. For qualitative approach transcrips were coded thematically. In Phase 2, context – specific antiretroviral treatment guidelines were developed to promote adherence to ART by adolescents and youths of Buffalo City Metropolitan Municipality district. Results: About 35percent of the participants indicated low adherence, 31percent for moderate adherence and 34percent for high adherence. A strong correlation between interpersonal relationship and adherence (p = 0.008), a correlation between aspect of care related to clinic and adherence (p = 0.028), a significant correlation between social support and adherence to ART (p = 0.006) and a significant relationship between self- efficacy and adherence to ART (p = 0.000) were obtained. No correlation between demographic status and adherence except for race. Results from the interviews revealed that barriers to adherence were more evident than enabling factors. Recommendations: Health service providers should strengthen ART adherence programmes for adolescents and youths by applying principles as they appear in the context – based guidelines.
- Full Text:
Inter-role conflict and coping strategies of employed mothers : a study of selected private schools in the Mthatha area of the Eastern Cape Province, South Africa
- Authors: Tegbe, Dzigbordi
- Date: 2017
- Subjects: Role conflict Working mothers Women -- Employment , Children of working mothers
- Language: English
- Type: Thesis , Masters , MSoc
- Identifier: http://hdl.handle.net/10353/7830 , vital:30768
- Description: Working women are finding it increasingly challenging to establish a balance between work and family life. This often results in work-family conflicts which affect women teachers’ well-being. The current study utilised role theory to investigate the effect of work-family conflicts on work related income, using the Mthatha community as case study. The study explored the impact of inter-role conflict on stress related illness and the coping strategies working women can adopt to create work-family balance. The motivation of the study is based on limited research regarding the impact of work-family on South African working mothers, where feminisation of labour force is compelling women to devote more time to their work roles thus neglecting their traditional roles as mothers. The research design used a cross section survey, and the sampling procedure applied a multi-stage concept of data collection, where both qualitative and quantitative methods were used to delve into the issues of inter-role conflict and coping strategies of employed mother-teachers, to establish causal relationships geared towards explaining the phenomena. The population consisted of working mothers in Mthatha private schools, where data was collected using a work-family conflict questionnaire. The results of the study established a positive relationship between the multi-tasking of mother-teachers and inter-role conflicts, and also confirmed that work roles/tasks have become overwhelming. Consequently, working women families are neglected, while support from extended families is not coming or is insufficient to alleviate the burdens of role conflicts. The conflicts lead to stress-related illnesses and individually, women are not interested in consulting psychologists to manage their stress. The women suffer ailments such as headaches, general pains, sleep dysfunction, high or low blood pressure, heart diseases, and become moody and tearful, expressing low self-esteem. Women teachers in Mthatha were of the view that proper strategies are needed to mitigate their stress. Some of these coping strategies involve a good condition of service at school, refraining from applying medication to solve stress, taking part in exercise and rest, and having a relaxing time with family and friends. The findings of this study can help through suggesting useful strategies that can be utilised by working teachers who are mothers to mitigate their inter-role conflict. It will also lead to more insight into role theories.
- Full Text:
- Authors: Tegbe, Dzigbordi
- Date: 2017
- Subjects: Role conflict Working mothers Women -- Employment , Children of working mothers
- Language: English
- Type: Thesis , Masters , MSoc
- Identifier: http://hdl.handle.net/10353/7830 , vital:30768
- Description: Working women are finding it increasingly challenging to establish a balance between work and family life. This often results in work-family conflicts which affect women teachers’ well-being. The current study utilised role theory to investigate the effect of work-family conflicts on work related income, using the Mthatha community as case study. The study explored the impact of inter-role conflict on stress related illness and the coping strategies working women can adopt to create work-family balance. The motivation of the study is based on limited research regarding the impact of work-family on South African working mothers, where feminisation of labour force is compelling women to devote more time to their work roles thus neglecting their traditional roles as mothers. The research design used a cross section survey, and the sampling procedure applied a multi-stage concept of data collection, where both qualitative and quantitative methods were used to delve into the issues of inter-role conflict and coping strategies of employed mother-teachers, to establish causal relationships geared towards explaining the phenomena. The population consisted of working mothers in Mthatha private schools, where data was collected using a work-family conflict questionnaire. The results of the study established a positive relationship between the multi-tasking of mother-teachers and inter-role conflicts, and also confirmed that work roles/tasks have become overwhelming. Consequently, working women families are neglected, while support from extended families is not coming or is insufficient to alleviate the burdens of role conflicts. The conflicts lead to stress-related illnesses and individually, women are not interested in consulting psychologists to manage their stress. The women suffer ailments such as headaches, general pains, sleep dysfunction, high or low blood pressure, heart diseases, and become moody and tearful, expressing low self-esteem. Women teachers in Mthatha were of the view that proper strategies are needed to mitigate their stress. Some of these coping strategies involve a good condition of service at school, refraining from applying medication to solve stress, taking part in exercise and rest, and having a relaxing time with family and friends. The findings of this study can help through suggesting useful strategies that can be utilised by working teachers who are mothers to mitigate their inter-role conflict. It will also lead to more insight into role theories.
- Full Text:
Relevance of the family assessment for least developed countries (FALDC) assessment tool rendering child protection services in the Eastern Cape, South Africa
- Authors: Mgidi, Siphelele
- Date: 2016
- Subjects: Child abuse -- South Africa -- Prevention Family social work -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6335 , vital:29578
- Description: Assessment tools have been used for various purposes, including for protecting children from maltreatment. The main aim of this study was to to evaluate and determine the relevance of the Family Assessment for Leased Developed Countries (FALDC) assessment tool for child protection services in the Eastern Cape Province. The research was conducted using the social developmental welfare approach (Patel, 2005) and ecological systems theory (Healy, 2005). The study made use of the qualitative research method; in doing so the study made use of the case study design. In using the qualitative research method, focus group discussions were conducted with 29 social workers involved in child protection services. The findings of the study indicated that the FALDC assessment tool provides information useful for child protection services even though it contains sections that are regarded as less relevant to child protection. The study also founded that the FALDC assessment tool is relevant to child protection in the South African context, yet it needs to be aligned so that it provides much of the information desired by those involved in child protection. A conclusion drawn from this study is that the FALDC assessment tool appears to be relevant for child protection services. The FALDC assessment tool needs to be adjusted taking into consideration other aspects important to child protection in the South African child protection context.
- Full Text:
- Authors: Mgidi, Siphelele
- Date: 2016
- Subjects: Child abuse -- South Africa -- Prevention Family social work -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6335 , vital:29578
- Description: Assessment tools have been used for various purposes, including for protecting children from maltreatment. The main aim of this study was to to evaluate and determine the relevance of the Family Assessment for Leased Developed Countries (FALDC) assessment tool for child protection services in the Eastern Cape Province. The research was conducted using the social developmental welfare approach (Patel, 2005) and ecological systems theory (Healy, 2005). The study made use of the qualitative research method; in doing so the study made use of the case study design. In using the qualitative research method, focus group discussions were conducted with 29 social workers involved in child protection services. The findings of the study indicated that the FALDC assessment tool provides information useful for child protection services even though it contains sections that are regarded as less relevant to child protection. The study also founded that the FALDC assessment tool is relevant to child protection in the South African context, yet it needs to be aligned so that it provides much of the information desired by those involved in child protection. A conclusion drawn from this study is that the FALDC assessment tool appears to be relevant for child protection services. The FALDC assessment tool needs to be adjusted taking into consideration other aspects important to child protection in the South African child protection context.
- Full Text:
- «
- ‹
- 1
- ›
- »