National Repository of Grey Literature 108 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Preparation Of Electrodes Of Li-S Batteries Using Inversely Vulcanized Sulfur
Bláha, Jakub
This paper focuses on manufacturing of Li-S batteries, which in theory have higherenergy density than the currently most popular Li-ion battery. Before putting the Li-S battery onthe market, several problems which prevent its practical use have to be solved. These issues includeshort longevity, which could be solved by manufacturing the electrode using inversely vulcanizedsulfur. This method could eliminate the immediate issue and enable the rise of the Li-S battery onthe market.
Numerical Modelling Of Li-S Chemistry
Mačák, Martin
This work presents a custom electrochemical model of a lithium-sulfur cell implemented into Ansys Fluent software. The model was used to analyse cyclic voltammetry at differently sized particles, which represented porous cathodes. The results indicate that the cyclic voltammetry response of the whole porous sulfur cathode could be solved as a response of a single particle, which might lead to a simplification of numerical simulations and in result, to accelerating their optimizing process.
Time-resolved potentiometry on liquid-liquid interface
Mansfeldová, Věra
MSc. Věra Mansfeldová Dissertation thesis: Time-resolved potentiometry on liquid-liquid interface Abstract The aim of this work is to explore the method of temporal resolution in potentiometry as a new prospective electrochemical analytical technique. In connection with interface of two immiscible electrolyte solutions (ITIES) it may find utilization in analytical chemistry. This technique up to my knowledge has not been published yet. Potential response of analyte on liquid/liquid interface includes both distribution processes, their temporal resolution and redox processes, which specificity can modified by changing the composition of individual phases. Unlike "classic" potentiometric techniques, limited just to potential determination, this method, which I have given the working name "time resolved potentiometry at liquid-liquid interface" utilizes time development of potential response, which was found to be an analyte-specific function. The time resolved potentiometry presented in this work includes time course of potential response to analytical parameters specific for particular analyte. It brings series of data characterizing the analyte in given environment in a similar manner as spectra and may allow creating analyte-specific data package - fingerprint. Combination with ITIES allows, unlike...
Thermodynamic modelling of hydrogen fuel cells
Nováček, Marek ; Pavelka, Michal (advisor) ; Němec, Tomáš (referee)
In this thesis, proton exchange membrane fuel cells are studied. At the beginning, the ideas underlying their function are exposed and some possibilities of usage are pre- sented. Thereafter, we aim to describe the processes inside the fuel cells with the aid of thermodynamics and in agreement with constitutive relations that have been obtained experimentally. Namely, we are interested in the fluxes of water and protons inside the membrane, where they are acted upon by thermodynamic forces, and the electrochemical reactions at the electrodes, which can be described by the Butler-Volmer equations. Also do we study the efficiency of the fuel cell by evaluating the production of entropy due to the diverse processes that take place in the fuel cell. It is the goal of the computational part of this thesis to propose a zero-dimensional model and compare it with the results provided in the supervisor's doctoral thesis. 1
Utilization of Working Silver Solid Electrode for Voltammetric Determination of Drug Metronidazole
Mráček, Ondřej ; Vyskočil, Vlastimil (advisor) ; Fischer, Jan (referee)
This Bachelor thesis discusses the electrochemical behavior of metronidazole and seeks to find optimal conditions for the drug's voltammetric determination at a working silver solid electrode (AgSE) using differential pulse voltammetry (DPV). The voltammetric behavior of the drug was investigated, where the dependent variable was the pH of a water medium Britton-Robinson buffer (BRB). The optimum medium for voltammetric determination of metronidazole at a AgSE is a region of cathodic potential chosen to be the Britton-Robinson buffer, where the sodium hydroxide alkaline component (Na-BRB) has a pH of 10.0, and then measured further at voltammetric cell (volume of 10 ml) at concentration dependencies in the range of (1-1000)×10−6 mol/l. The limit of quantification (LOQ) and the limit of detection (LOD) were found to be 1.8×10−6 mol/l and 5.5×10−7 mol/l, respectively. In addition, the metronidazole was studied for the effect of electrochemical regeneration at the AgSE, where the parameters were: Nr = 150, Ein_r = 0 mV, Tin_r = 0.1 s, Efin_r = −1500 mV, Tfin_r = 0.1 s. The next section studies the electrochemical activity of the AgSE, which is not entirely ideal. The newly developed method might be applicable in the future for determining metronidazole through differential pulse voltammetry (DPV) to...
Voltammetry with Preliminary Extraction as a New Approach for Rapid Determination of Formaldehyde in Wood-Based Products
Dvořák, Pavel ; Vyskočil, Vlastimil (advisor) ; Dejmková, Hana (referee)
The aim of the presented Diploma Thesis was to develop a new method for the indirect determination of formaldehyde in wood-based products using gas-diffusion microextraction coupled with electrochemical detection on unmodified screen-printed electrodes (MLEM-SPCE). Formaldehyde released from the sample is derivatized using an acetylacetone reagent present in an acceptor solution. The product of derivatization of formaldehyde with acetylacetone is 3,5-diacetyl-1,4-dihydrolutidine (DDL) which forms a selective oxidation voltammetric peak at a potential of 0.4 V. Detection and quantification limits of 0.57 mg kg−1 and 1.89 mg kg−1 , respectively, were obtained, together with intra- and inter-day precision below 10% (as relative standard deviation, RSD). The developed methodology was applied to determine formaldehyde content in seven samples. Similar results were obtained from the European standard method EN 717-3 with a significant reduction of total analysis time. The developed method MLEM-SPCE, which combines the use of a new sample preparation procedure for volatile compounds with the firstly introduced determination of formaldehyde (as the derivative product DDL) on unmodified SPCEs, proves to be a promising alternative for the determination of formaldehyde in wood-based products and other samples.
Research report No. 2/2019 on structure and morphology and chemical/electrochemical analysis of\nthe samples provided by HE3DA
Zukalová, Markéta
The report contains the results of X-ray, chemical and morphology analysis carried out on the provided\nsamples set and their electrochemical evaluation.
New Strategies in Electrochemical Detection of DNA Damage Induced by Interaction with UV radiation
Přibylová, Monika ; Vyskočil, Vlastimil (advisor) ; Fischer, Jan (referee)
V této bakalářské práci byl zkoumán netradiční redoxní indikátor 5-nitro-1,10-fenantrolin jako možný ukazatel poškození DNA. Měření probíhalo elektrochemicky technikou diferenční pulzní voltametrie v tříelektrodovém zapojení. Jako pracovní elektroda byla použita elektroda z ultračistého grafitu, která byla modifikována nízkomolekulární DNA z lososích spermií. Poškození DNA probíhalo pomocí UVC záření o vlnové délce 254 nm. Byl studován rozdíl výšky voltametrických signálů 5-nitro-1,10-fenantrolinu mezi nepoškozenou a poškozenou DNA. Nově vyvinuté metody se ukázaly jako slibné pro detekci míry poškození DNA v závislosti na čase ozařování a v závislosti na vzdálenosti od zdroje ozařování. Poškození DNA bylo rozsáhlejší u obou studovaných faktorů v závislosti na jejich rostoucích hodnotách. Klíčová slova Elektrochemie DNA biosenzory Netradiční elektrodové materiály Poškození DNA Biologicky aktivní látky Záření
Characterization of electronic properties of nanowires for electrochemistry
Kovařík, Martin ; Čech, Vladimír (referee) ; Kolíbal, Miroslav (advisor)
Elektrochemické metody nacházejí využití v mnoha aplikacích (např. senzorice, skladování el. energie nebo katalýze). Jejich nespornou výhodou je nízká finanční náročnost na přístrojové vybavení. Abychom lépe porozuměli procesům probíhajícím na elektrodách, je dobré znát elektronickou pásovou strukturu materiálu elektrody. Úkolem této práce je vyhodnotit výstupní práci a pozici hrany valenčního pásu nových materiálů pro elektrody, konkrétně cínem dopovaného oxidu india pokrytého nanotrubicemi sulfidu wolframičitého. Ultrafialová fotoelektronová spektroskopie a Kelvinova silová mikroskopie jsou metody použité pro tuto analýzu. Zvláštní důraz je kladen na přípravu vzorků elektrod pro měření, aby nedošlo k nesprávné interpretaci výsledků vlivem vnějších efektů jako je např. kontaminace nebo modifikace povrchu.
Thermodynamic analysis of solid oxide cells
Vágner, Petr ; Maršík, František (advisor) ; Grmela, Miroslav (referee) ; Pekař, Miloslav (referee)
Thermodynamic analysis of solid oxide cells Petr Vágner The thesis deals with continuum thermodynamic modeling and analysis of phe- nomena in solid oxide electrochemical cells. A general description of the evo- lution of charged mixtures using partial mass densities, momentum density, entropy density, electric induction, magnetic field, polarization, and magnetiza- tion based on the GENERIC framework is formulated. The formulation is used to recover the Landau-Lifshitz magnetization relaxation model, the Single Re- laxation Time model for dielectrics, and the generalized Poisson-Nernst-Planck model. The latter model is consequently linked to the second part, where a novel double layer model of an yttria-stabilized zirconia interface is formulated within non-equilibrium thermodynamics. The model is solved for numerically in the time domain, and cyclic voltammetry of the system is analyzed. The last part of the thesis demonstrates the limits of Exergy Analysis on a simple solid oxide hydrogen fuel cell model with non-isothermal boundary. It is demon- strated that the minimization of entropy production does not necessarily lead to the maximization of the electric power for certain optimization scenarios. The thesis consists of a compilation of published and unpublished results of the author.

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