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Abstract  

YBaCo4O7 compound is capable to intake and release a large amount of oxygen in the temperature range of 200–400°C. In the present study, the effect of Zn, Ga and Fe substitution for Co on the oxygen adsorption/desorption properties of YBaCo4O7 were investigated by thermogravimetry (TG) method. Due to fixed oxidation state of Zn2+ ions, the substitution of Zn2+ for Co2+ suppresses the oxygen adsorption of YBaCo4−xZnxO7. The substitution of Ga3+ for Co3+ also decreases the oxygen absorption capacity of YBaCo4−xGaxO7. This can be explained by the strong affinity of Ga3+ ions towards the GaO4 tetrahedron. Compared with Zn- and Ga-substituted samples, the drop of oxygen adsorption capacity is smallest for Fe-substituted samples because of the similar changeability of oxidation states of Co and Fe ions.

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the anions. Catalytic properties of oxysalts were compared with their oxygen sorption capacities, which depend on the electron donor properties of the oxysalt cation (the centre of oxygen adsorption). The activities of the catalysts in the propene

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Abstract  

The back-titration of atomic oxygen chemisorbed on metallic copper using carbon monoxide is investigated by microcalorimetry. Results from simulations based on a microkinetic model of the back-titration are used for processing of microcalorimetric data. In addition, surface oxidation of copper by nitrous oxide is investigated by microcalorimetry. The results are compared with results obtained by nitrous oxide reactive frontal chromatography and by static oxygen adsorption studied by microcalorimetry. The heat of adsorption of nitrous oxide on copper amounts to 304 kJ mol−1, and the heat of adsorption of carbon monoxide on surfaceoxidized copper is in the range from 120 to 70 kJ mol−1.

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Abstract

The influence of pH shift and NaCl salting on the heat production, oxygen adsorption, and oxygen evolution rates of the unicellular green halotolerant microalga Dunaliella maritima and the freshwater microalga Chlorella vulgaris were investigated. In the growth process of both microalgae the alkalization of their culture medium was observed. And simultaneously it was shown that at increasing NaCl salting of cultural medium its acidification occurs. At alkalization and acidification of Chlorella medium the increase of heat production and respiration rates were observed. At alkalization and acidification of Dunaliella culture the adverse effect of decreasing heat production rate was observed. Acidification of culture medium of both algae led to short-term and sharp increase of photosynthesis measured by polarography and photomicrocalorimeter.

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from the oxygen adsorption at 473 K using an earlier obtained isotherm of oxygen adsorption on silver powder [ 10 ]. To investigate the reactivity in reactions ( II ), surface hydroxides were prepared by oxygen adsorption at 473 K on a pure

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concentration of the available electrons on the surface at each temperature, then the extent of oxygen adsorption on the same sample, could be defined the relative decrease of σ in dry oxygen (as a result of electron trapping by oxygen ad-ions): where is the

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area is screening the oxygen adsorption in this temperature range. Fig. 4 Arrhenius plots of conductivity—the influence of humidity The sample prepared by coprecipitation is, by

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) represent the balance of the rates of reactions ( 17 – 20 ) and oxygen adsorption. To proceed further on, we focus on one the most important cases when (i) reactions ( 17 – 20 ) are relatively slow and (ii) NH 3 is close to adsorption

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Reaction Kinetics, Mechanisms and Catalysis
Authors: Viorel Chihaia, Karl Sohlberg, M. Scurtu, C. Hornoiu, M. Caldararu, C. Munteanu, G. Postole, N. I. Ionescu, T. Yuzhakova, and A. Redey

dispersion, the oxygen adsorption ability of SnO 2 must be diminished by the presence of surface alumina in its proximity, as alumina provides water molecules, which compete with oxygen on the same adsorption sites of SnO 2 [ 14 ]. As shown, the presented

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Reaction Kinetics, Mechanisms and Catalysis
Authors: Viorel Chihaia, Karl Sohlberg, B. Grzybowska-Świerkosz, M. Ruszel, R. Grabowski, L. Kępiński, M. A. Małecka, and J. Sobczak

the Au/oxide interface. As mentioned in the introduction, these vacancies are suggested as centers for oxygen adsorption and dissociation, providing active oxygen species for oxidation [ 6 – 9 ]. On the other hand, these vacancies may be the centers of

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