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Found in: ključnih besedah
Summary of found: ...fuel cell, ethanol oxidation, graphene, oxygen reduction, catalyst, pt-free, electrochemical impedance spectroscopy...
Keywords: fuel cell, ethanol oxidation, graphene, oxygen reduction, catalyst, pt-free, electrochemical impedance spectroscopy
Published: 03.12.2020; Views: 2047; Downloads: 0
Fulltext (5,31 MB)

Abstract: The study explores the potential of immobilized TiO2-based zeolite composite photocatalyst (TiO2-FeZ) made of commercial AEROXIDE TiO2 P25 and iron-exchanged zeolite of ZSM5 type (FeZ), for solar assisted treatment of diclofenac (DCF), pharmaceutical included in the ‘‘watch list” during last prioritization in water legislation by EU. In this study the efficiency of applied photocatalytic treatment, solar/TiO2-FeZ/H2O2, of DCF water solution was evaluated on basis of DCF removal and conversion kinetics, as well as the changes of common parameters for assessing water quality. Hence, the changes in the removal and mineralization of overall organic content, biodegradability, toxicity to Vibrio fischeri, dechlorination of DCF and its formed by-products, were monitored during the treatment. The obtained data were correlated with the evolution of DCF by-products, identified and monitored during the treatment by HPLC/MSMS analysis. In order to estimate the influence of water matrix, all experiments were performed in the presence of chloride or sulphate as counter ions. The obtained data revealed that degradation mechanism of DCF by applied treatment process using immobilized TiO2-FeZ includes the adsorption onto photocatalyst surface and consequent degradation. The contribution of homogeneous Fenton reaction due to leached iron ions was found to be negligible. The adsorption and degradation pathway of DCF were influenced by the type of counter ions, which was reflected in the observed changes of water quality parameters.
Found in: ključnih besedah
Keywords: Solar photocatalysis, TiO2-FeZ catalyst, Diclofenac, Degradation pathway, Biodegradability, Toxicity
Published: 21.07.2016; Views: 4674; Downloads: 0
Fulltext (2,10 MB)

Abstract: The goal of this research is to establish the working state and correlations between atomic structure and catalytic activity of nanoshaped CuO/CeO2 catalysts used in N2O decomposition reaction. The catalysts contained CuO nanoclusters dispersed over different CeO2 morphologies: nano-rods and nano-cubes. N2O is a side product of nitric and adipic acid production and a very potent greenhouse gas that is formed in amounts estimated at about 400 Mt/a of CO2 equivalent. Consequently, the development of robust, active and selective catalysts for N2O decomposition is of a great environmental and economical interest. CeO2-based materials promoted by CuO represent a new class of catalysts that exhibit considerable activity in N2O decomposition reaction between 300 and 500 °C [1-3], and are significantly cheaper and more efficient than Pt, Pd or Rh based catalysts. In order to maximize the efficiency of the catalyst, the active site in this reaction needs to be identified and the mechanism clarified. In-situ Cu K-edge and Ce L3-edge XANES and EXAFS analysis was done on a set of CuO/CeO2 catalysts with different ceria morphology (nano-cubes, nano-rods) and Cu loadings between 2 to 8 wt. %, during N2O decomposition reaction, under controlled reaction conditions at 400 °C. The XAS spectra were measured in-situ, in a tubular reactor, filled with protective He atmosphere at 1 bar, first at RT, then during heating, and at final temperature of 400 °C, during catalytic reaction, when the catalyst was exposed to a small amount (0.2 vol%) of N2O mixed with He. The Cu K-edge and Ce L3-edge XANES and EXAFS analysis reveals changes in valence and local structure of Cu and Ce in the CuO/CeO2 catalysts. In the initial state (in He at RT), copper is present in the form of CuO nanoparticles attached to the CeO2 surface. After heating in He to 400 °C, partial (10%) reduction of Ce [Ce(IV)→Ce(III)] is detected, significant part of Cu(II) is reduced to Cu(I) and Cu(0) species, and direct Cu-Cu bonds are formed. During catalytic N2O decomposition at 400°C, all Ce(III) is oxidized back to Ce(VI), and a major part of Cu is oxidized back to Cu(II), with about 5% of Cu(I) remaining in equilibrium state. Observed structural and valence changes of copper strongly depend on its loading and CeO2 morphology. With systematic In-situ XAS analysis of different nanoshaped CuO/CeO2 catalysts, we identified the structural characteristics and changes of Cu and Ce phases during catalytic N2O decomposition reaction, which could lead to identification of the active catalytic site during the reaction and further improve the performance of these promising catalytic materials.
Found in: ključnih besedah
Summary of found: ...structure and catalytic activity of nanoshaped CuO/CeO2 catalysts used in N2O decomposition reaction. The catalysts...
Keywords: EXAFS, CuO/CeO2 catalyst, N2O decomposition
Published: 12.09.2018; Views: 2998; Downloads: 0
Fulltext (281,07 KB)

Abstract: Aims:Preparation of the new metals - polymeric composite, Met x-EPS (I), to be used as a green catalyst in water or in two-phase aqueous conditions. Study Design: Recovery and valorization of polymetallic wastes to obtain directly new catalysts using a microorganism to explore their application in removal of difficult and dangerous chemical pollutants present in aqueous environment
Found in: ključnih besedah
Keywords: Metals - polymeric composite, biogenerated polymetallic exopolysaccharide, new catalyst from metallic wastes, hydrodechlorination of PCBs in water
Published: 06.05.2019; Views: 2702; Downloads: 0
Fulltext (373,55 KB)

Abstract: The development of affordable, low-iridium-loading, scalable, active, and stable catalysts for the oxygen-evolution reaction (OER) is a requirement for the commercialization of proton-exchange membrane water electrolyzers (PEMWEs). However, the synthesis of high-performance OER catalysts with minimal use of the rare and expensive element Ir is very challenging and requires the identification of electrically conductive and stable high-surface-area support materials. We developed a synthesis procedure for the production of large quantities of a nanocomposite powder containing titanium oxynitride (TiONx) and Ir. The catalysts were synthesized with an anodic oxidation process followed by detachment, milling, thermal treatment, and the deposition of Ir nanoparticles. The anodization time was varied to grow three different types of nanotubular structures exhibiting different lengths and wall thicknesses and thus a variety of properties. A comparison of milled samples with different degrees of nanotubular clustering and morphology retention, but with identical chemical compositions and Ir nanoparticle size distributions and dispersions, revealed that the nanotubular support morphology is the determining factor governing the catalyst’s OER activity and stability. Our study is supported by various state-of-the-art materials’ characterization techniques, like X-ray photoelectron spectroscopy, scanning and transmission electron microscopies, Xray powder diffraction and absorption spectroscopy, and electrochemical cyclic voltammetry. Anodic oxidation proved to be a very suitable way to produce high-surface-area powder-type catalysts as the produced material greatly outperformed the IrO2 benchmarks as well as the Ir-supported samples on morphologically different TiONx from previous studies. The highest activity was achieved for the sample prepared with 3 h of anodization, which had the most appropriate morphology for the effective removal of oxygen bubbles.
Found in: ključnih besedah
Summary of found: ...development of affordable, low-iridium-loading, scalable, active, and stable catalysts for the oxygen-evolution reaction (OER) is a requirement...
Keywords: electrocatalysis, oxygen-evolution reaction, TiONx-Ir powder catalyst, iridium nanoparticles, anodic oxidation, morphology−activity correlation
Published: 04.01.2021; Views: 1802; Downloads: 0
Fulltext (6,36 MB)