Topic
Oxygen
About: Oxygen is a research topic. Over the lifetime, 48149 publications have been published within this topic receiving 1113788 citations. The topic is also known as: O & Oxygen.
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TL;DR: In this article, surface area measurement, X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements were performed to study the surface and bulk oxygen mobility and to correlate it to the activity.
Abstract: Co 3 O 4 , CeO 2 and Co 3 O 4 –CeO 2 mixed oxides with Co/Ce nominal atomic ratio 0.1:5, prepared by co-precipitation method with sodium carbonate, were tested in the oxidation of propene under lean condition and the catalyst stability was checked by performing three consecutive heating–cooling cycles. Characterization of the textural properties were performed by surface area measurement BET, X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. Among the Co 3 O 4 –CeO 2 mixed oxides, Co 3 O 4 (30 wt%)–CeO 2 (70 wt%) gives the best activity attaining full propene conversion at 250 °C. This sample is characterized by the presence of Co 3 O 4 particles well dispersed and in good contact with ceria according to BET and XRD data and as evidenced by SEM micrographs. Oxygen temperature-programmed desorption (O 2 -TPD) and C 3 H 6 -temperature-programmed reduction (C 3 H 6 -TPR) experiments were carried out in order to study the surface and bulk oxygen mobility and to correlate it to the activity. At temperature around 200 °C, O 2 -TPD experiments showed the desorption of mobile surface oxygen species for the most active samples, Co 3 O 4 and Co 3 O 4 (30 wt%)–CeO 2 (70 wt%). C 3 H 6 -TPR experiments for both of the oxides also evidenced a high reactivity at low temperature, especially, for Co 3 O 4 (30 wt%)–CeO 2 (70 wt%) giving at 345 °C an intense peak of CO 2 formation. Conversely, the ceria sample showed by C 3 H 6 -TPR much less pronounced oxygen bulk mobility, starting to react with propene above 500 °C and forming only CO. In this case, the catalytic activity of ceria was explained in terms of formation of surface oxygen vacancies which are relevant to the propene oxidation in presence of gaseous oxygen.
234 citations
TL;DR: Co3O4/Co2MnO4 nanocomposites, derived from a single-source CoMn-layered double hydroxide precursor, exhibit excellent bifunctional oxygen electrode activities for both oxygen reduction and evolution reactions, which can be attributed to the large specific surface area and well-dispersed heterogeneous structure of the nanocom composites.
Abstract: Co3O4/Co2MnO4 nanocomposites, derived from a single-source CoMn-layered double hydroxide precursor, exhibit excellent bifunctional oxygen electrode activities for both oxygen reduction and evolution reactions, which can be attributed to the large specific surface area and well-dispersed heterogeneous structure of the nanocomposites.
234 citations
TL;DR: In this article, the aprotic polar solve is used to solve the problem of oxygen reduction in nonaqueous electrolyte solutions containing Li salts, which is a complex field of research involving solution reactions with oxygen radicals and lithium oxides.
Abstract: Oxygen reduction in nonaqueous electrolyte solutions containing Li salts is a complex field of research involving solution reactions with oxygen radicals and lithium oxides. The aprotic polar solve...
233 citations
TL;DR: Mitochondria catalysed a rapid rate of NO breakdown, which was greater in the absence of oxygen and was partly inhibited by cyanide and azide, suggesting that at least part of the NO breakdown was due to reduction of NO by cytochrome oxidase.
Abstract: Nitric oxide (NO) inhibited the respiration rate of mitochondria isolated from rat heart at sub-micromolar concentrations of NO. The inhibition was rapidly and completely reversible, indicating that NO does not damage mitochondria. The sensitivity of respiration to NO depended on the oxygen concentration, substrate type and respiratory state of the mitochondria, consistent with NO competing with oxygen at cytochrome oxidase. Mitochondria catalysed a rapid rate of NO breakdown, which was greater in the absence of oxygen and was partly inhibited by cyanide and azide, suggesting that at least part of the NO breakdown was due to reduction of NO by cytochrome oxidase. The rapid rate of this breakdown suggests that mitochondrial breakdown of NO may be significant physiologically.
233 citations
01 Jan 1987
TL;DR: This chapter discusses the metabolism of activated oxygen species, which consists of the superoxide radical anion, O 2, hydrogen peroxide, H 2 O 2 ; the OH radical type of oxidant (OH . ); and singlet oxygen, 1 O 2.
Abstract: This chapter discusses the metabolism of activated oxygen species. Oxygen exists as atomic oxygen, dioxygen, trioxygen, and several charged derivatives. Within these forms different energy levels are found because of their individual electronic configurations. The biologically important oxygen species are: (1) the superoxide radical anion, O 2 ; (2) hydrogen peroxide, H 2 O 2 ; (3) the OH radical type of oxidant (OH . ); and (4) singlet oxygen, 1 O 2 . The superoxide radical anion is formed by one electron reduction of ground-state dioxygen. The first stable product of both monovalent and divalent oxygen reduction is hydrogen peroxide, H 2 O 2 . Hydrogen peroxide can be converted into the strongly oxidizing OH radical (OH . ) by one-electron transfer. Singlet oxygen, 1 O 2 (1Δ g ) is a physically energized form of dioxygen. In contrast to ground-state dioxygen, 1 O 2 has Π* electrons with antiparallel spins; thus, its reactions with other ground-state atoms or molecules are not spin restricted and proceed at appreciable rates.
233 citations