61 research outputs found

    Successful immobilization of lanthanides doped TiO2 on inert foam for repeatable hydrogen generation from aqueous ammonia

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    We describe the successful possibility of the immobilization of a photocatalyst on foam, which is beneficial from a practical point of view. An immobilized photocatalyst is possible for use in a continuous experiment and can be easily separated from the reactor after the reaction concludes. Parent TiO2, La/TiO2, and Nd/TiO2 photocatalysts (containing 0.1 wt.% of lanthanide) were prepared by the sol-gel method and immobilized on Al2O3/SiO2 foam (VUKOPOR A) by the dip-coating method. The photocatalysts were investigated for the photocatalytic hydrogen generation from an aqueous ammonia solution under UVA light (365 nm). The evolution of hydrogen was compared with photolysis, which was limited to zero. The higher hydrogen generation was observed in the presence of 0.1 wt.% La/TiO2 than in 0.1 wt.% Nd/TiO2. This is, besides other things, related to the higher level of the conduction band, which was observed for 0.1 wt.% La/TiO2. The higher conduction band's position is more effective for hydrogen production from ammonia decomposition.Web of Science135art. no. 125

    The role of fluorine in F-La/TiO2 photocatalysts on photocatalytic decomposition of methanol-water solution

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    F-La/TiO2 photocatalysts were studied in photocatalytic decomposition water-methanol solution. The structural, textural, optical, and electronic properties of F-La/TiO2 photocatalysts were studied by combination of X-ray powder diffraction (XRD), nitrogen physisorption, Ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), Electrochemical impedance spectroscopy (EIS), and X-ray fluorescence (XPS). The production of hydrogen in the presence of 2.8F-La/TiO2 was nearly up to 3 times higher than in the presence of pure TiO2. The photocatalytic performance of F-La/TiO2 increased with increasing photocurrent response and conductivity originating from the higher amount of fluorine presented in the lattice of TiO2.Web of Science1218art. no. 286

    Synthesis of vacant graphitic carbon nitride in argon atmosphere and its utilization for photocatalytic hydrogen generation

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    Graphitic carbon nitride (C3N4) was synthesised from melamine at 550 degrees C for 4 h in the argon atmosphere and then was reheated for 1-3 h at 500 degrees C in argon. Two band gaps of 2.04 eV and 2.47 eV were observed in all the synthetized materials. Based on the results of elemental and photoluminescence analyses, the lower band gap was found to be caused by the formation of vacancies. Specific surface areas of the synthetized materials were 15-18 m(2)g(-1) indicating that no thermal exfoliation occurred. The photocatalytic activity of these materials was tested for hydrogen generation. The best photocatalyst showed 3 times higher performance (1547 mu mol/g) than bulk C3N4 synthetized in the air (547 mu mol/g). This higher activity was explained by the presence of carbon (V-C) and nitrogen (V-N) vacancies grouped in their big complexes 2V(C) + 2V(N) (observed by positron annihilation spectroscopy). The effect of an inert gas on the synthesis of C3N4 was demonstrated using Graham ' s law of ammonia diffusion. This study showed that the synthesis of C3N4 from nitrogen-rich precursors in the argon atmosphere led to the formation of vacancy complexes beneficial for hydrogen generation, which was not referred so far.Web of Science121art. no. 1362

    Photocatalytic H-2 evolution, CO2 reduction, and NOx oxidation by highly exfoliated g-C3N4

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    g-C3N4, with specific surface area up to 513 m(2)/g, was prepared via three successive thermal treatments at 550 degrees C in air with gradual precursor mass decrease. The obtained bulk and exfoliated (1ex, 2ex and 3ex) g-C3N4 were characterized and tested as photocatalysts for H-2 production, CO2 reduction and NOx oxidation. The exfoliated samples demonstrated graphene-like morphology with detached (2ex) and sponge-like framework (3ex) of layers. The surface area increased drastically from 20 m(2)/g (bulk) to 513 m(2)/g (3ex). The band gap (E-g) increased gradually from 2.70 to 3.04 eV. Superoxide radicals (O-center dot(2)-) were mainly formed under UV and visible light. In comparison to the bulk, the exfoliated g-C3N4 demonstrated significant increase in H-2 evolution (similar to 6 times), CO2 reduction (similar to 3 times) and NOx oxidation (similar to 4 times) under UV light. Despite the E-g widening, the photocatalytic performance of the exfoliated g-C3N4 under visible light was improved too. The results were related to the large surface area and low e(-)-h(+) recombination. The highly exfoliated g-C3N4 demonstrated selectivity towards H-2 evolution reactions.Web of Science1010art. no. 114

    Photocatalytic reduction of CO2 over Ti3+ self-doped TiO2-based nanomaterials

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    In this study, we explored the photocatalytic efficacy of Ti3+-doped TiO2-based photocatalysts for CO2 reduction. The Ti3+ self-doped photocatalysts were synthesized using a straightforward chemical reduction with sodium borohydride (NaBH4). Our investigation aimed to elucidate the intricate interplay between the synthesis process and the quantity of NaBH4 reductant on the physical-chemical and photocatalytic attributes of the defective TiO2-based photocatalysts. We explored three different commercially available TiO2 materials labeled P25, (S)TiO2, and KRONOClean7050, which were reduced (2 g of TiO2) with 0.75 and 1.5 g of NaBH4. The reduction with 0.75 g of NaBH4 led to a significant decrease of photocatalytic activity in all three cases. It was caused by clogging of the photocatalysts surface by sodium ions which resulted in the surface recombination of charge carriers. Oppositely, the reduction with 1.5 g of NaBH4, led to an increase of the photocatalytic activity with superior performance of KRONOClean7050. The comprehensive characterization of all the samples explained this superior performance of KC7050_RED_1.5 sample. Importantly, it did not contain any amorphous phase and the crystal size was two times higher compared to other 2 samples reduced by 1.5 g of NaBH4. In the addition to higher crystallinity, the formation of a disordered TiO2−x layer, enriched with Ti3+ defects and oxygen vacancies, was confirmed. These structural features enhance the light absorption and mitigate undesired recombination of photogenerated charge carriers. These results would trigger farther investigation of defect engineering towards enhancement of the efficiency of metal oxide photocatalysts.European Union's Horizon 2020 project SAN4Fuel, (101079384, HORIZON-WIDERA-2021-ACCESS-03–01); European Commission, EC, (101120397, CZ.10.03.01/00/22_003/0000048, HORIZON-WIDERA-2022-TALENTS, RRC/12/2022); Grantová Agentura České Republiky, GA ČR, (GA CR 21-24268K); Narodowe Centrum Badań i Rozwoju, NCBR, (NOR/POLNORCCS/PhotoRed/0007/2019-00)Large Research Infrastructure ENREGAT [LM2023056]; Norway Grants 2014-2021 via the National Centre for Research and Development [NOR/POLNORCCS/PhotoRed/0007/2019-00]; Czech Science Foundation [GA CR 21-24268K]; European Union [HORIZON-WIDERA-2021-ACCESS-03-01: 101079384, CZ.10.03.01/00/22_003/0000048]; Support for Science and Research in the Moravia- Silesia Region 2022 [RRC/12/2022]; APPROACH [101120397

    The Legal Status of Minors and Other Vulnerable Applicants for International Protection

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    Persons who seek international protection in the European Union are entitled to number of rights contained in the EU law, international law and national law. Some applicants for international protection are entitled to additional rights and guarantees due to their weakened position. This thesis analyses the legal position of vulnerable applicants for international protection (or more precisely applicants with special needs). The position of minor applicants is dealt with in more detail. The thesis further deals with the legislation of the Common European Asylum System, attention is also paid to the European Court of Human Right's case- law, to the UN Convention on the Rights of the Child and to other relevant documents. All applicants for international protection can be seen as vulnerable. In the view of the European Court of Human Rights applicant for international protection is "as such, a member of a particularly underprivileged and vulnerable population group in need of special protection". The EU law does not explicitly describe applicants as vulnerable, but it entitles them to a certain standard of rights by which it reflects their difficult position. Furthermore, the Reception Conditions Directive and Asylum Procedures Directive define applicants with special needs (more precisely applicants..

    Use of mortgage loans in personal finances management

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    Předložená diplomová práce je zaměřená na využití hypotečních úvěrů v souvislosti s osobními financemi klienta. Cílem práce je zjistit výhodnost využití hypotečního úvěru jako finanční páky. Metodická část vysvětluje základní pojmy a matematické vzorce použité v této práci. V teoretické části je popsána problematika hypotečního úvěru, vývoj hypotečních úvěrů v ČR a možnosti zhodnocení volných finančních prostředků klienta včetně investičního rozhodování. Praktická část řeší situaci modelového klienta v různých scénářích a variantách, které zohledňují faktory ovlivňující jejich výnosnost. V závěru práce je provedeno shrnutí výsledků a doporučení pro klienta.ObhájenoThis submitted diploma thesis is focused on the use of mortgage loans in connection with the client's personal finances. The aim of this work is to find out the advantage of using a mortgage loan as financial leverage. The methodical part explains the basic terms and mathematical formulas used in this work. The theoretical part describes the issue of mortgage loans, the development of mortgage loans in Czech Republic and the possibility of evaluating the client's free funds, including investment decisions. The practical part solves the situation of the model client in various scenarios and variants that take into account the factors affecting their profitability. At the end of the work is a summary of results and recommendations for the client

    The Legal Status of Minors and Other Vulnerable Applicants for International Protection

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    Persons who seek international protection in the European Union are entitled to number of rights contained in the EU law, international law and national law. Some applicants for international protection are entitled to additional rights and guarantees due to their weakened position. This thesis analyses the legal position of vulnerable applicants for international protection (or more precisely applicants with special needs). The position of minor applicants is dealt with in more detail. The thesis further deals with the legislation of the Common European Asylum System, attention is also paid to the European Court of Human Right's case- law, to the UN Convention on the Rights of the Child and to other relevant documents. All applicants for international protection can be seen as vulnerable. In the view of the European Court of Human Rights applicant for international protection is "as such, a member of a particularly underprivileged and vulnerable population group in need of special protection". The EU law does not explicitly describe applicants as vulnerable, but it entitles them to a certain standard of rights by which it reflects their difficult position. Furthermore, the Reception Conditions Directive and Asylum Procedures Directive define applicants with special needs (more precisely applicants...Osoby, které v Evropské unii žádají o mezinárodní ochranu, požívají práva, která jim přiznává právo EU, mezinárodní právo i vnitrostátní legislativa. Některým žadatelům o mezinárodní ochranu jsou ale přiznávána zvláštní práva a záruky, protože je jejich postavení v určitém ohledu oslabené. Tato diplomová práce analyzuje postavení zranitelných žadatelů o mezinárodní ochranu (resp. žadatelů se zvláštními potřebami) a větší pozornost věnuje nezletilým žadatelům o mezinárodní ochranu. Diplomová práce zkoumá především úpravu ve Společném evropském azylovém systému, pozornost je ale též věnována judikatuře Evropského soudu pro lidská práva, Úmluvě OSN o právech dítěte a dalším relevantním dokumentům mezinárodního práva. Na všechny žadatele o mezinárodní ochranu lze nahlížet jako na zranitelné. Evropský soud pro lidská práva ve své judikatuře žadatele o mezinárodní ochranu označil jako "zvláště neprivilegovanou a zranitelnou skupinu, která potřebuje speciální ochranu". Unijní úprava všechny žadatele o mezinárodní ochranu jako zranitelné explicitně nepopisuje, poskytuje jim ale určitý standard práv, čímž reflektuje jejich postavení. Nadto přijímací a procedurální směrnice vymezují žadatele zvláštními potřebami (resp. žadatele, kteří potřebují zvláštní procesní záruky a žadatele se zvláštními potřebami při...Katedra evropského právaDepartment of European LawFaculty of LawPrávnická fakult

    Effect of ZnO preparation method on the photocatalytic decomposition of ammonia in aqueous suspensions

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    Import 22/07/2015Diplomová práce se zabývá vlivem metody přípravy oxidu zinečnatého na fotokatalytický rozklad amoniaku, přičemž jako modelová reakční směs byl použit hydroxid amonný. Fotokatalytickým rozkladem vznikal vodík a dusík. Fotokatalytický rozklad amoniaku byl realizován ve vsádkovém anulárním míchaném reaktoru se suspendovaným fotokatalyzátorem. Ve středu symetrie reaktoru byla umístěna UV lampa poskytující záření s vlnovou délkou 254 nm. Fotokatalyzátor oxid zinečnatý byl připraven třemi různými způsoby a to: tepelným žíháním octanu zinečnatého (ZnO(1)), srážecí reakcí octanu zinečnatého a hydroxidu sodného s následným tepelným žíháním (ZnO(2)) a srážecí reakcí octanu zinečnatého hydroxidem sodným při UV záření a s následným tepelným žíháním (ZnO(3)). Připravené nanočástice byly charakterizovány termogravimetrií, rentgenovou difrakční analýzou, UV-Vis spektroskopií, fotoluminiscenční spektroskopií, fyzisorpcí dusíku a transmisní elektronovou mikroskopií. Při fotokatalytickém i fotochemickém rozkladu modelové reakční směsi docházelo k produkci vodíku. Produkce vodíku v přítomnosti ZnO fotokatalyzátorů byla srovnávána s produkcí H2 v přítomnosti komerčně vyráběného fotokatalyzátoru TiO2 Evonik P25. Aktivita testovaných katalyzátorů klesala v pořadí: ZnO(1) < ZnO(3) = Evonik P25 < ZnO(2). Experimentální data fotokatalytického rozkladu amoniaku byla vyhodnocena integrální metodou, byly určeny kinetické konstanty a byl potvrzen předpoklad, že reakci lze popsat rovnicí 1. řádu. Korelací fotokatalytické aktivity a fyzikálně-chemických charakteristik připravených fotokatalyzátorů bylo zjištěno, že klíčovými parametry ovlivňující fotokatalytický rozklad amoniaku jsou odlišné defekty v krystalové mřížce ZnO (kyslíkové vakance (VO) nebo kyslík intersticiální (Oi) a kyslík v místě Zn (OZn)), které vznikají v důsledku různé přípravy fotokatalyzátorů. Nejaktivnější fotokatalyzátor ZnO(1), který byl připraven tepelným žíháním, měl nejmenší specifický povrch, ale současně nejmenší množství kyslíkových vakancí. Nejmenší aktivitu fotokatalyzátoru ZnO(2) připraveného srážecí reakcí lze přisoudit nejvyššímu množství kyslíkových vakancí. Tyto vakance zachytávají excitované elektrony, které pak nejsou k dispozici pro fotokatalytickou reakci.This thesis examines the influence of the preparation method of zinc oxide on the photocatalytic decomposition of ammonia, where as ammonium hydroxide was used as a model reaction mixture. Hydrogen and nitrogen were generated by photocatalytic decomposition of ammonia. The photocatalytic decomposition of ammonia was carried out in a batch annular stirred reactor with suspended photocatalyst. In the axis of symmetry of the reactor the UV lamp providing a radiation having a wavelength of 254 nm was placed. Zinc oxide photocatalyst was prepared by three different ways, namely: thermal annealing of zinc acetate (ZnO(1)), precipitation reaction of zinc acetate and sodium hydroxide followed by thermal annealing (ZnO(2)) and a precipitation reaction of zinc acetate with sodium hydroxide under the UV radiation and followed by thermal annealing (ZnO(3)). Prepared nanoparticles were characterized by thermogravimetry, X-ray diffraction analysis, UV-Vis spectroscopy, photoluminescence spectroscopy, nitrogen physisorption and transmission electron microscopy. The hydrogen production was observed in both, photocatalytic and photochemical decomposition of model reaction mixture. The hydrogen production in the presence of a ZnO photocatalysts was compared to the production of H2 in the presence of a commercially manufactured photocatalyst TiO2 Evonik P25. The activity of tested photocatalysts was decreasing in this order: ZnO(1) < ZnO(3) = Evonik P25 < ZnO(2). Experimental data of the photocatalytic decomposition of ammonia were evaluated by integral method, kinetic constants were calculated and the assumption the reaction can be described by the equation of 1st order was confirmed. Based on the correlation between the photocatalytic activity and physico-chemical characteristics of prepared photocatalysts. It was found out the key parameters influencing photocatalytic decomposition of ammonia are different defects in the crystal lattice of the ZnO oxygen vacancies (VO) or interstitial oxygen (Oi) and the oxygen in the place of Zn (OZn) which originate from different preparation way of photocatalysts. The most active photocatalyst ZnO(1), which was prepared by thermal annealing, had the lowest specific surface area, but also the lowest amount of oxygen vacancies. The lowest activity of ZnO(2) photocatalyst, prepared by precipitation reaction, can be attributed to the highest amount of oxygen vacancies. These vacancies capture excited electrons, which arenot available for the photocatalytic reaction itself.619 - Katedra fyzikální chemie a teorie technologických pochodůvýborn

    Czech identity, national interests and right-wing political parties 2002-2006

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    Práce sleduje dva základní cíle. Prvním cílem je pojmenovat a analyzovat teoretická východiska, za která jsou považována osvětlení a vymezení pojmů národní identita, nacionalismus a národní zájmy. Záměrem této časti práce je poskytnout základní teoretický rámec pro užívání těchto pojmů. Druhým cílem je analýza pravicové politiky (u etablovaných pravicových a krajně pravicových politických stran) s důrazem na vymezené pojmy, jejich používání jako aktivizačních témat a zmapování nacionálních tendencí mezi parlamentními volbami v letech 2002-2006
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