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Investigation of new anode materials for methanol polymer fuel cells
Fiala, Roman ; Matolín, Vladimír (advisor) ; Sofer, Zdeněk (referee)
We investigated new types of anode catalysts for polymer membrane fule cell (PEMFC). Pt doped CeO2 thin lms were deposited by rf-magnetron sputtering on carbon nanotubes (CNTs) directly grown on GDL by using CVD. We observed considerable increase of speci c power by 1000 times and more in comparison with standard PtRu anode catalyst. For this new anode system we obtained the speci c power of 44.3 W/mg(Pt). The interaction of Pt with CeO2 layers with di erent substrates was investigated by using photoelectron spectroscopy. The results showed that platinum was in cationic state and the Pt2+/Pt4+ ratio was dependent of substrates materials. We also demonstrated that the performance of direct methanol fuel cell with Pt and PtRu catalyst can be dramatically increased simply by adding sodium hydroxide to methanol fuel. Cell voltage and power output characteristics were studied in dependence on current, temperature and concentration of sodium hydroxide. Endurance test was performed and the fuel cell exhibited stable response. Power density of 80.7 mW/cm2 was recorded for 2 M methanol/2 M sodium hydroxide fuel 30řC.
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The preparation and study of catalytic system Cu(O)-CeO2 using surface analytical methods
Šmíd, Břetislav ; Matolínová, Iva (advisor) ; Plšek, Jan (referee) ; Sofer, Zdeněk (referee)
Title: The preparation and study of catalytic system Cu(O)-CeO2 using surface analytical methods Author: Břetislav Šmíd Department: Department of Surface and Plasma Science Supervisor of the doctoral thesis: Doc. Mgr. Iva Matolínová, Dr. Abstract: This work is concerned with a study of copper/copper oxide - cerium dioxide systems and their interaction with CO and H2O molecules. Investigated samples were prepared in the form of powder catalysts and also as very well defined model inverse systems. The low temperature CO oxidation powder catalysts were studied by means of XPS, XRD, SEM, TEM and in micro-reactor system allowing the CO oxidation examination. The study of H2O adsorption and co-adsorption of H2O with CO were carried out on model inverse systems CeOx(111)/Cu(111) in ultra-high vacuum conditions using X-ray, synchrotron radiation (SRPES), resonant (RPES) photoelectron spectroscopies and LEED. It was observed on the stoichiometric surface water adsorbs molecularly at 120 K while on the reduced surface and surface of CeO2 islands on Cu(111) the H2O adsorption is partially dissociative with formation of OH groups. The increase of Ce3+ species (i.e. surface reduction) observed after H2O adsorption was explained as an electronic effect of the Ce 4f charge accumulation and Ce 5d charge depletion....
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Investigation of new anode materials for methanol polymer fuel cells
Fiala, Roman ; Sofer, Zdeněk (referee) ; Matolín, Vladimír (advisor)
We investigated new types of anode catalysts for polymer membrane fule cell (PEMFC). Pt doped CeO2 thin lms were deposited by rf-magnetron sputtering on carbon nanotubes (CNTs) directly grown on GDL by using CVD. We observed considerable increase of speci c power by 1000 times and more in comparison with standard PtRu anode catalyst. For this new anode system we obtained the speci c power of 44.3 W/mg(Pt). The interaction of Pt with CeO2 layers with di erent substrates was investigated by using photoelectron spectroscopy. The results showed that platinum was in cationic state and the Pt2+/Pt4+ ratio was dependent of substrates materials. We also demonstrated that the performance of direct methanol fuel cell with Pt and PtRu catalyst can be dramatically increased simply by adding sodium hydroxide to methanol fuel. Cell voltage and power output characteristics were studied in dependence on current, temperature and concentration of sodium hydroxide. Endurance test was performed and the fuel cell exhibited stable response. Power density of 80.7 mW/cm2 was recorded for 2 M methanol/2 M sodium hydroxide fuel 30řC.
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Preparation of gold, silver and platinum colloid solutions by precursors decomposition in low temperature plasma
Brožek, Vlastimil ; Kutílek, Zdeněk ; Mastný, L. ; Sýkora, V. ; Benešová, L. ; Sofer, Z.
Liquid precursor decomposition in the low temperature plasma generated by WSP® was used for synthesis of precious metals nanoparticles. The gold in the form of H[AuCl4], silver in the form of AgNO3 and platinum in the form of H2[PtCl6] were used to generate colloid solutions with concentration of 5 mg.l-1 – 70 mg.l-1 and particle size of 20 nm – 120 nm. The solution contained elevated concentration of nitrite and nitrate ions due to the reaction of plasma with nitrogen form air. In order to reduce the concentration of nitrite and nitrate ions the plasma generated nanoparticles was projected by plasma torch to the ammonium chloride solution. Other way used for reduction of NO3- and NO2- concentration was optimization of geometry of plasma system. The other way was also by application of shrouding effect by nitrogen and ammonia gas. The size of nanoparticles and their concentration can be influenced by geometry of plasma torch, composition of carrier gas and by geometry of
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Production of nanoparticles utilizing water stabilized plasma
Bertolissi, Gabriele ; Brožek, Vlastimil ; Chráska, Tomáš ; Mušálek, Radek ; Neufuss, Karel ; Mastný, L. ; Sofer, Z.
Water stabilized plasma torch (WSP®) generates plasma jet with max. plasma velocity in the nozzle exit 7000m/s and temperature of 25000-30000 K. Reactants injected into the plasma jet undergo complicated radical reactions. Interaction of plasma with injected reactants depends on energy settings of the WSP plasma torch and lasts from 5 to 10 ms. Droplets of inorganic compound solution are fed to the plasma jet by pressurized spray nozzle device. Compounds of AgI,AlIII,TiIV,PtIV,VV, and CrVI undergo decomposition in the extremely high plasma temperature and the decomposed products are collected in liquid separators. Size of the produced nanoparticles in unsettled fraction is from 10 to 200 nm and depends primarily on concentration of inputting aerosol particles. In the case of 15 seconds reaction time and use of saturated solutions at 20°C, one can obtain colloidal solutions with silver, platinum, alumina, titania, vanadia, and chromia nanoparticles in concentrations of 3 to 180mg
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