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Study of manganeese oxides properties by the EQCM method
Pléha, David ; Špičák, Petr (referee) ; Novák, Vítězslav (advisor)
The present work deals with the use of manganese oxide as a catalyst for positive electrode of fuel cells. The theoretical part is to analyze the problem of fuel cells, focusing on lowtemperature fuel cells. Are discussed and the methods of measurement and evaluation of properties of manganese oxide layer. The practical part deals with doping electrolytic manganese dioxide salts of divalent metals and monitoring their behavior in the cyclic voltammetry by the EQCM method.
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Study of Metal Oxides and Hydroxides in Aqueous Solutions
Špičák, Petr ; Trnková, Libuše (referee) ; Kadlec, Jaromír (referee) ; Kazelle, Jiří (advisor)
This dissertation work deals with analysis of nickel hydroxide phases, their oxidation compounds, their stability and degradation mechanisms of electrochemically more active alpha phase on standard beta phase. The active material was prepared by both methods, electrodeposition and chemical precipitation. Main analysis method was Electrochemical Quartz Crystal Microbalance in combination with common analytical methods (cyclic voltammetry, potenciometry) can resolute between alpha and beta phases and quantitatively describe differences in main reaction by monitoring mass changes in the active material. Poor stability of the ?-Ni(OH)2 were improved by adding cations with valence two three and four into the structure instead of Ni atoms. The most important role plays cobalt and its hydroxide. Totally new way is to use titanium in combination with other cations. In electrolyte the most significant addition is LiOH, which has beneficial influent on cycle ability, stability in strong alkaline medium and cycle life.
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Investigation of mass changes by piezoelectric resonator
Kužílek, Jakub ; Svoboda, Vít (referee) ; Špičák, Petr (advisor)
An operation deals with a concept of the new cell for measuring weight changes with high precision through the use of quartz crystal micro-scales called QCM. The new cell is destined for crystal resonators which diameter is 14mm. The resonators are produced in the Czech Republic. A price is the greatest advantage of crystal resonators in comparison with original crystals. The next positive is higher mechanical tolerance which is outgoing of a guest-size. The cell designed by this way is tested in electrochemical system where a deposition of metallic copper in crystal is happening. A homologation of accuracy is judged by Faraday’s law and using Sauerbrey equation for quartz crystal microbalance in cyclic voltammetry measurement method.
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A Study of Phenomena that Limit the Life-Span of Ni-Zn Secondary Cells
Chladil, Ladislav ; Oriňáková,, Renáta (referee) ; Vanýsek,, Petr (referee) ; Novák, Vítězslav (advisor)
This dissertation is focused on the study of selected additives and their effect on positive and negative electrodes of Ni-Zn secondary cells. The first group of additives consists of the inorganic compounds that reduce zinc oxide solubility and thus prevents shape changes of the zinc electrode. The second group contains organic additives that have the beneficial effect of dendrite growth prevention. All additives were examined in relationship to their compatibility with the positive electrode and to their effect on the zinc electrode dendrites inhibition, hydrogen evolution and corrosion inhibition. Moreover, the study of decomposition kinetics of supersaturated zincate solution with the first group of additives was performed. Finally, a short study of pulse regime charging mode with regard to dendrites inhibition was performed and evaluated.
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The influence of cobalt additive on parameters of positive electrode for Ni-Cd accumulators
Svoboda, Michal ; Svoboda, Vít (referee) ; Špičák, Petr (advisor)
The Master´s thesis deals with description of the influence of cobalt additive on positive electrode parameters for Ni-Cd accumulators. Trough the use of Electrochemical Quartz Crystal Microbalance are analysed the effects which decline effective life of positive electrode during accelerated cycling. Theoretical part describes important characteristics of Ni-Cd accumulators, the working principle and effects which are in progress on positive electrode during cycling. The next part deals with description of system EQCM and the pricnciples of doping active mass with cobalt additive. Practical part consists of EQCM system calibration and electrochemical measurements. The principal aim is detection of the influence of cobalt additve on active mass during cycling in different electrolytes. From the results of measurements is set the optimal amount of cobalt additive.
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A Study of Phenomena that Limit the Life-Span of Ni-Zn Secondary Cells
Chladil, Ladislav ; Oriňáková,, Renáta (referee) ; Vanýsek,, Petr (referee) ; Novák, Vítězslav (advisor)
This dissertation is focused on the study of selected additives and their effect on positive and negative electrodes of Ni-Zn secondary cells. The first group of additives consists of the inorganic compounds that reduce zinc oxide solubility and thus prevents shape changes of the zinc electrode. The second group contains organic additives that have the beneficial effect of dendrite growth prevention. All additives were examined in relationship to their compatibility with the positive electrode and to their effect on the zinc electrode dendrites inhibition, hydrogen evolution and corrosion inhibition. Moreover, the study of decomposition kinetics of supersaturated zincate solution with the first group of additives was performed. Finally, a short study of pulse regime charging mode with regard to dendrites inhibition was performed and evaluated.
|
|
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Study of Metal Oxides and Hydroxides in Aqueous Solutions
Špičák, Petr ; Trnková, Libuše (referee) ; Kadlec, Jaromír (referee) ; Kazelle, Jiří (advisor)
This dissertation work deals with analysis of nickel hydroxide phases, their oxidation compounds, their stability and degradation mechanisms of electrochemically more active alpha phase on standard beta phase. The active material was prepared by both methods, electrodeposition and chemical precipitation. Main analysis method was Electrochemical Quartz Crystal Microbalance in combination with common analytical methods (cyclic voltammetry, potenciometry) can resolute between alpha and beta phases and quantitatively describe differences in main reaction by monitoring mass changes in the active material. Poor stability of the ?-Ni(OH)2 were improved by adding cations with valence two three and four into the structure instead of Ni atoms. The most important role plays cobalt and its hydroxide. Totally new way is to use titanium in combination with other cations. In electrolyte the most significant addition is LiOH, which has beneficial influent on cycle ability, stability in strong alkaline medium and cycle life.
|
|
|
Investigation of mass changes by piezoelectric resonator
Kužílek, Jakub ; Svoboda, Vít (referee) ; Špičák, Petr (advisor)
An operation deals with a concept of the new cell for measuring weight changes with high precision through the use of quartz crystal micro-scales called QCM. The new cell is destined for crystal resonators which diameter is 14mm. The resonators are produced in the Czech Republic. A price is the greatest advantage of crystal resonators in comparison with original crystals. The next positive is higher mechanical tolerance which is outgoing of a guest-size. The cell designed by this way is tested in electrochemical system where a deposition of metallic copper in crystal is happening. A homologation of accuracy is judged by Faraday’s law and using Sauerbrey equation for quartz crystal microbalance in cyclic voltammetry measurement method.
|
|
|
Study of manganeese oxides properties by the EQCM method
Pléha, David ; Špičák, Petr (referee) ; Novák, Vítězslav (advisor)
The present work deals with the use of manganese oxide as a catalyst for positive electrode of fuel cells. The theoretical part is to analyze the problem of fuel cells, focusing on lowtemperature fuel cells. Are discussed and the methods of measurement and evaluation of properties of manganese oxide layer. The practical part deals with doping electrolytic manganese dioxide salts of divalent metals and monitoring their behavior in the cyclic voltammetry by the EQCM method.
|
|
|
The influence of cobalt additive on parameters of positive electrode for Ni-Cd accumulators
Svoboda, Michal ; Svoboda, Vít (referee) ; Špičák, Petr (advisor)
The Master´s thesis deals with description of the influence of cobalt additive on positive electrode parameters for Ni-Cd accumulators. Trough the use of Electrochemical Quartz Crystal Microbalance are analysed the effects which decline effective life of positive electrode during accelerated cycling. Theoretical part describes important characteristics of Ni-Cd accumulators, the working principle and effects which are in progress on positive electrode during cycling. The next part deals with description of system EQCM and the pricnciples of doping active mass with cobalt additive. Practical part consists of EQCM system calibration and electrochemical measurements. The principal aim is detection of the influence of cobalt additve on active mass during cycling in different electrolytes. From the results of measurements is set the optimal amount of cobalt additive.
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