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Nonplatinum catalysts for polymer exchange membrane fuel cells
Talába, Michal ; Chladil, Ladislav (referee) ; Novák, Vítězslav (advisor)
This work brings a study about non-platinum catalysts, alkaline membranes and methods that interprets catalytic activity. Work deals with a research on non-platinum catalysts based on MnO2 with addition of support substances, measuring of their properties using cyclic voltammetry and hydrodynamics theory. Also a fuel cell measurement of catalytic materials on PVA membrane is executed. The outcome of this work is evaluation of voltammetry and fuel cell measurements. The results of all methods are compared too.
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Vanillylmandelic and Homovanillic Acid: Electroanalysis at Carbon-Based Electrodes
Baluchová, Simona ; Schwarzová, Karolina (advisor) ; Dejmková, Hana (referee)
The objective of the present work is the study of the electrochemical behaviour of two diagnostic tumor markers of great importance, vanillylmandelic acid (VMA) and homovanillic acid (HVA), on carbon-based electrodes by using cyclic and differential pulse voltammetry. A comparison was made among non-modified glassy carbon electrode (GCE) and GCE modified by multi-walled carbon nanotubes, Nafion (Nafion/GCE) and poly(neutral red) (PNR/GCE), and further boron doped diamond (BDD) electrode which was activated by anodic polarization (Eakt = +2,4 V, t = 30 s) or by polishing on alumina slurry. Significant differences in the voltammetric responses of VMA and HVA were found, not only among utilized electrode materials which also influenced the way of controlling the oxidation process, but also they depend on the pH value of aqueous media in which these acids occurred. An acidic environment is the most suitable for their determination. Calibration dependences were measured in 0.1 mol∙l−1 phosphate buffer pH 3.0 which was chosen as an optimal supporting electrolyte for differential pulse voltammetric determination. Achieved detection limits were 0.6, 0.9, 0.8 and 1.2 μmol∙l−1 for HVA and 0.4, 1.5, 2.4 and 1.1 μmol∙l−1 for VMA at BDD electrode, non-modified GCE, Nafion/GCE and PNR/GCE, respectively. Limits...
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Voltammetric determination of clinical markers vanillylmandelic and homovanillic acid at boron-doped diamond electrode
Baluchová, Simona ; Schwarzová, Karolina (advisor) ; Zima, Jiří (referee)
This thesis investigates electrochemical oxidation of two main catecholamine metabolites vanillylmandelic and homovanillic acid at anodically oxidized boron-doped diamond electrode using voltammetric techniques. Their behavior in aqueous media depends on its pH value significantly; the highest and best developed voltammetric signals are provided in an acidic medium when both organic compounds occur in their non-ionized form. The phosphate buffer pH 3.0 was chosen as supporting electrolyte for analysis of these two substances and the conditions of determination were optimized. Calibration dependences are linear for both studied compounds in the concentration range from 4 to 100 μmol∙l−1 . Using differential pulse voltammetry limits of detection for homovanillic acid (LOD = 0.57 μmol∙l−1 ) and for vanillylmandelic acid (LOD = 0.41 μmol∙l−1 ) were achieved. The possibility of their simultaneous determination at boron-doped diamond was also verified. The oxidation mechanisms of homovanillic acid and vanillylmandelic acid at boron-doped diamond electrode were studied by cyclic voltammetry and in both cases it is diffusion-controlled reaction.
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Nonplatinum catalysts for polymer exchange membrane fuel cells
Talába, Michal ; Chladil, Ladislav (referee) ; Novák, Vítězslav (advisor)
This work brings a study about non-platinum catalysts, alkaline membranes and methods that interprets catalytic activity. Work deals with a research on non-platinum catalysts based on MnO2 with addition of support substances, measuring of their properties using cyclic voltammetry and hydrodynamics theory. Also a fuel cell measurement of catalytic materials on PVA membrane is executed. The outcome of this work is evaluation of voltammetry and fuel cell measurements. The results of all methods are compared too.
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