Showing papers on "Oxygen published in 2020"
TL;DR: In this paper, the role of oxygen vacancy defects in the activation-oxidation process of toluene was investigated, and the as-prepared MnOx-ET catalyst has more surficial oxygen vacancies and good oxygen storage capacity.
Abstract: To elucidate the role of oxygen vacancy defects, various Mn-based oxides with oxygen vacancy defects are employed to the toluene oxidation, which are synthesized by adjusting solvent and double-complexation routes. The MnOx-ET catalyst shows the highest catalytic activity (T90 = 225 °C) for toluene oxidation. Compared with other Mn-based oxides, the as-prepared MnOx-ET catalyst has more surficial oxygen vacancies and good oxygen storage capacity (OSC), which is the reason on its remarkable activity for toluene oxidation. In addition, in situ DRIFTS study reveals that both lattice oxygen and adsorbed oxygen species can participate in the activation-oxidation process of toluene, which results in two reaction routes for the toluene oxidation. The rich oxygen-vacancy concentration of catalysts accelerates the key steps for the activation and generation of oxidized products. Quasi-in situ XPS results further confirm that enrich adsorbed-oxygen species as active oxygen and increasing Mn4+ concentration enhance the superior activity for toluene oxidation.
377 citations
TL;DR: The structure-performance relationship of α-, β-, γ- and δ-MnO2 catalysts was studied in this paper, where four samples exhibited different activities of toluene oxidation in terms of distinct tunnel sizes, surface-active oxygen and redox properties.
Abstract: The structure-performance relationship of α-, β-, γ- and δ-MnO2 catalysts were studied. The four samples exhibited different activities of toluene oxidation in terms of distinct tunnel sizes, surface-active oxygen and redox properties. δ-MnO2 catalyst with K+ in the mezzanines of its layers presented the highest toluene oxidation activity under a GHSV of 60,000 mL·g−1 h−1, as well as good water resistance. HAADF images and EELS results showed that oxygen vacancies preferred to form on δ-MnO2 lattice with layer stack dislocations via Mn4+ reduction rather than β-MnO2 with good crystallization. These inherent-distorted structures with heterocations K+ improved the emerge-annihilate cycling of oxygen vacancies. In-situ DRIFTS results showed that toluene adsorption was facilitated via rapid dehydrogenation of methyl due to abundant surface adsorbed oxygen on δ-MnO2. In addition, benzoate, maleic and manganese carbonate on δ-MnO2 were the key intermediate species during toluene oxidation at relatively low temperatures.
345 citations
TL;DR: A multicomponent FeCoCrNi alloy with dynamically formed Ni4+ species to offer high catalytic activity via lattice oxygen activation mechanism to offer highly intrinsic activity at low applied potentials is reported.
Abstract: Anodic oxygen evolution reaction (OER) is recognized as kinetic bottleneck in water electrolysis. Transition metal sites with high valence states can accelerate the reaction kinetics to offer highly intrinsic activity, but suffer from thermodynamic formation barrier. Here, we show subtle engineering of highly oxidized Ni4+ species in surface reconstructed (oxy)hydroxides on multicomponent FeCoCrNi alloy film through interatomically electronic interplay. Our spectroscopic investigations with theoretical studies uncover that Fe component enables the formation of Ni4+ species, which is energetically favored by the multistep evolution of Ni2+→Ni3+→Ni4+. The dynamically constructed Ni4+ species drives holes into oxygen ligands to facilitate intramolecular oxygen coupling, triggering lattice oxygen activation to form Fe-Ni dual-sites as ultimate catalytic center with highly intrinsic activity. As a result, the surface reconstructed FeCoCrNi OER catalyst delivers outstanding mass activity and turnover frequency of 3601 A gmetal−1 and 0.483 s−1 at an overpotential of 300 mV in alkaline electrolyte, respectively. Electrocatalytic water oxidation is facilitated by high valence states, but these are challenging to achieve at low applied potentials. Here, authors report a multicomponent FeCoCrNi alloy with dynamically formed Ni4+ species to offer high catalytic activity via lattice oxygen activation mechanism.
270 citations
TL;DR: The preparation of bimetallic oxides and oxygen co-doped g-C3N4 was successfully prepared, which was an effective PMS activator for degradation of toxic organic pollutants and cycling experiments demonstrated the good stability of Fe-Co-O-g-C 3N4.
Abstract: Graphite carbon nitride (g-C3N4) has a stable structure but poor catalytic capability for activating peroxymonosulfate (PMS). In this study, the codoping of g-C3N4 with bimetallic oxides (iron and cobalt) and oxygen was investigated to enhance its catalytic capability. The results showed that iron, cobalt, and oxygen codoped g-C3N4 (Fe-Co-O-g-C3N4) was successfully prepared, which was capable of completely degrading sulfamethoxazole (SMX) (0.04 mM) within 30 min, with a reaction rate of 0.085 min-1, indicating the superior catalytic activity of Fe-Co-O-g-C3N4. The mineralization efficiency of SMX was 22.1%. Sulfate radicals and singlet oxygen were detected during the process of PMS activation. However, the role that singlet oxygen played in degrading SMX was not obvious. Surface-bound reactive species and sulfate radicals were responsible for SMX degradation, in which sulfate radicals contributed to 46.6% of SMX degradation. The superior catalytic activity was due to the synergistic effect of metal oxides and O-g-C3N4, in which O-g-C3N4 could act as a carrier and an activator as well as an electron mediator to promote the conversion of Fe(III) to Fe(II) and Co(III) to Co(II). Four main steps of SMX degradation were proposed, including direct oxidation of SMX, bond fission of N-C, bond fission of N-S, and bond fission of S-C. The effect of the pH, temperature, PMS concentration, chloridion, bicarbonate, and humic acids on SMX degradation was investigated. Cycling experiments demonstrated the good stability of Fe-Co-O-g-C3N4. This study first reported the preparation of bimetallic oxide and oxygen codoped g-C3N4, which was an effective PMS activator for degradation of toxic organic pollutants.
258 citations
TL;DR: Oxygen K-edge X-ray absorption spectra of both molecules and solids and the general analysis of the 3d transition metal oxides including discussions of the crystal field effect and the effects and trends in oxidation state and covalency are discussed.
Abstract: We review oxygen K-edge X-ray absorption spectra of both molecules and solids. We start with an overview of the main experimental aspects of oxygen K-edge X-ray absorption measurements including X-ray sources, monochromators, and detection schemes. Many recent oxygen K-edge studies combine X-ray absorption with time and spatially resolved measurements and/or operando conditions. The main theoretical and conceptual approximations for the simulation of oxygen K-edges are discussed in the Theory section. We subsequently discuss oxygen atoms and ions, binary molecules, water, and larger molecules containing oxygen, including biomolecular systems. The largest part of the review deals with the experimental results for solid oxides, starting from s- and p-electron oxides. Examples of theoretical simulations for these oxides are introduced in order to show how accurate a DFT description can be in the case of s and p electron overlap. We discuss the general analysis of the 3d transition metal oxides including discussions of the crystal field effect and the effects and trends in oxidation state and covalency. In addition to the general concepts, we give a systematic overview of the oxygen K-edges element by element, for the s-, p-, d-, and f-electron systems.
225 citations
204 citations
TL;DR: The conversion of carbon dioxide (CO2) into high-value chemical products has become a dramatic research area because of the efficient exploitation of carbon resources and simultaneous r....
Abstract: Electrochemical conversion of carbon dioxide (CO2) into high-value chemical products has become a dramatic research area because of the efficient exploitation of carbon resources and simultaneous r...
200 citations
TL;DR: In this article, the co-effects of Bi metal nanoparticles and oxygen vacancies in defective photocatalyst were investigated, and fundamental guidance for maintaining the active role of oxygen vacancies was provided.
Abstract: Surface oxygen vacancies can normally enhance photocatalytic activity, but also easily suffers from instability and deactivation in continuous photocatalytic purification of air pollutants. Therefore, it is necessary to develop an effective method to improve the photocatalytic stability of oxygen vacancies. In this work, Bi metal nanoparticle decorated Bi2O2CO3 nanosheets with oxygen vacancy (Bi@OV-BOC) are fabricated and exhibited higher photocatalytic activity and stability than Bi2O2CO3 with oxygen vacancy (OV-BOC). The co-effect of Bi metal nanoparticles and oxygen vacancies could also effectively inhibit the formation of toxic intermediates (NO2) and promote it to form final products (NO3−). First-principles density functional theory (DFT) calculation and experimental results suggested that the co-effects of Bi metal nanoparticles and oxygen vacancies (OVs) can largely promote the separation and transfer of photo-generated electron and hole to generate abundant active radicals. More importantly, the Bi metal nanoparticles could be as the active site to activate O2 and H2O molecules so that the O2 and H2O molecules would not fill into oxygen vacancies, resulting in preventing the deactivation of oxygen vacancies. The sufficient active radicals can realize complete oxidation of intermediates into final products and avoid toxic intermediates (e.g. NO2) accumulation. This study reveals the co-effects of Bi and OVs in defective photocatalyst, and also provides fundamental guidance for maintaining the active role of oxygen vacancies.
197 citations
TL;DR: In this paper, the effect and mechanism of oxygen vacancy occupancy on enhancing piezocatalytic activity of BaTiO3 nanobelt was investigated and showed that the presence of oxygen vacancies could efficiently adsorb and activate O2 on the surface of the nano-branch and consequently enhance the performance.
Abstract: BaTiO3 nanobelt featuring controlled oxygen vacancies, namely BTO-OV-X (X represents time (h) of vacuum heat-treatment), were prepared to systematically investigate the effect of oxygen vacancies occupancy on pizeocatalytic performance for degradation of organic pollutant. Remarkably, the creation of oxygen vacancies on BaTiO3 can mediate the piezocatalytic activity. The piezocatalytic activity exhibited a volcano-type trend with increasing oxygen vacancies. Results from first-principles density functional theoretical (DFT) calculations and O2-temperature programmed desorption (O2-TPD) measurement indicated that the presence of oxygen vacancies could efficiently adsorb and activate O2 on the surface of BaTiO3 nanobelt and consequently enhance piezocatalytic activity. Importantly, with the aid of piezoresponse force microscopy (PFM) measurement, the intrinsic reason of volcano-type trend of oxygen vacancy-activity was well unveiled. This work reveals the effect and mechanism of oxygen vacancy occupancy on enhancing piezocatalytic activity of BaTiO3 nanobelt and will shed light on design of efficient piezocatalysts in the future.
179 citations
TL;DR: In this paper, the authors showed that presence of oxygen vacancies significantly reduced adsorption energy and accelerated electron transfer, which further facilitated peroxymonosulfate (PMS) activation.
Abstract: Natural illite microsheets were firstly utilized to induce oxygen vacancies into ultrafine cobalt oxide (Co3O4) for highly efficient Fenton-like catalysis via activation of peroxymonosulfate (PMS). The results indicated that presence of illite microsheets regulated multi-directional crystallization of Co3O4 nanospheres and resulted in reduced grain size and crystallinity. The smaller grain size provided more reactive edge sites for PMS catalysis. The numerous indistinct lattice boundaries caused by reduced crystallinity created abundant oxygen vacancies. Density functional theory (DFT) calculations illustrated that presence of oxygen vacancies significantly reduced adsorption energy and accelerated electron transfer, which further faciliated PMS activation. The oxygen vacancy-rich Co3O4/illite exhibited superior catalytic efficiency in real water matrix. Apart from sulfate and hydroxyl radicals, singlet oxygen generated from oxygen vacancy-based reaction pathway also played a significant role in atrazine degradation. This strategy provided a new insight for future designing of natural mineral-based catalysts for efficient wastewater treatment via Fenton-like process.
179 citations
TL;DR: With the elevated temperatures, lattice oxygen of the catalysts facilitates the decomposition of aromatic rings and further improve the oxidation of toluene to CO2.
Abstract: Catalytic combustion technology is one of the effective methods to remove VOCs such as toluene from industrial emissions. The decomposition of an aromatic ring via catalyst oxygen vacancies is usually the rate-determining step of toluene oxidation into CO2. Series of CeO2 probe models were synthesized with different ratios of surface-to-bulk oxygen vacancies. Besides the devotion of the surface vacancies, a part of the bulk vacancies promotes the redox property of CeO2 in toluene catalytic combustion: surface vacancies tend to adsorb and activate gaseous O2 to form adsorbed oxygen species, whereas bulk vacancies improve the mobility and activity of lattice oxygen species via their transmission effect. Adsorbed oxygen mainly participates in the chemical adsorption and partial oxidation of toluene (mostly to phenolate). With the elevated temperatures, lattice oxygen of the catalysts facilitates the decomposition of aromatic rings and further improves the oxidation of toluene to CO2.
TL;DR: It is demonstrated that by modulating the oxygen functional groups near the atomically dispersed cobalt sites with proper electrochemical/chemical treatments, a highly active and selective oxygen reduction process for hydrogen peroxide production can be obtained in acidic electrolyte, showing a negligible amount of onset overpotential and nearly 100% selectivity within a wide range of applied potentials.
Abstract: Hydrogen peroxide produced by electrochemical oxygen reduction reaction provides a potentially cost effective and energy efficient alternative to the industrial anthraquinone process. In this study, we demonstrate that by modulating the oxygen functional groups near the atomically dispersed cobalt sites with proper electrochemical/chemical treatments, a highly active and selective oxygen reduction process for hydrogen peroxide production can be obtained in acidic electrolyte, showing a negligible amount of onset overpotential and nearly 100% selectivity within a wide range of applied potentials. Combined spectroscopic results reveal that the exceptionally enhanced performance of hydrogen peroxide generation originates from the presence of epoxy groups near the Co–N4 centers, which has resulted in the modification of the electronic structure of the cobalt atoms. Computational modeling demonstrates these electronically modified cobalt atoms will enhance the hydrogen peroxide productivity during oxygen reduction reaction in acid, providing insights into the design of electroactive materials for effective peroxide production. The production of hydrogen peroxide by electrochemical oxygen reduction is an attractive alternative to the industrial process, but catalysts should be optimized. Here, the authors enhance hydrogen peroxide production in acidic media with epoxy groups near cobalt centers on carbon nanotubes.
TL;DR: In this paper, a facile redox method was introduced to fabricate a series of MnO2 samples by varying the concentration of K+, which efficiently modulated the layer size, morphology, crystallinity, redox properties, and thus the surface active oxygen species of the obtained δ-MnO2.
Abstract: Engineering MnO2 with rich surface active oxygen species is critical to effectively eliminate formaldehyde (HCHO) under mild conditions. Herein, we introduced a facile redox method to fabricate a series of δ-MnO2 samples by varying the concentration of K+, which efficiently modulated the layer size, morphology, crystallinity, redox properties, and thus the surface active oxygen species of the obtained δ-MnO2. The medium potassium concentration led to the optimized Mn O bond strength, the abundant surface active oxygen species, and the complete conversion of ca. 22 ppm HCHO at 30 °C under a weight hourly space velocity (WHSV) of 200,000 mL/(gcat h). Surface adsorbed oxygen species (e.g., O2− and O−) and surface hydroxyl groups, were suggested to oxidize HCHO into intermediates (i.e., DOM, formate, and carbonate species). Water was critical for further transforming the intermediates into CO2. A Langmuir-Hinshelwood (LH) mechanism was proposed involving in the whole oxidation process.
TL;DR: In this article, bimetallic Fe-Ca oxides were synthesized to be used as oxygen carriers to promote the hydrogen production from the chemical looping gasification of rice straw.
TL;DR: The results exemplify the feasibility to tailor the active lattice oxygen of perovskite by modulating the distortion of BO6 in ABO3, which ultimately influences their reaction performance in chemical looping processes.
Abstract: Modulating lattice oxygen in metal oxides that conducts partial oxidation of methane in balancing C-H activation and syngas selectivity remains challenging. This paper describes the discovery of distorting FeO6 octahedra in La1-xCexFeO3 (x = 0, 0.25 0.5, 0.75, 1) orthorhombic perovskites for the promotion of lattice oxygen activation. By combined electrical conductivity relaxation measurements and density functional theory calculations studies, this paper describes the enhancement of FeO6 octahedral distortion in La1-xCexFeO3 promoting their bulk oxygen mobility and surface oxygen exchange capability. Consequently, La0.5Ce0.5FeO3 with the highest FeO6 distortion achieves exceptional syngas productivity of ∼3 and 8 times higher than LaFeO3 and CeFeO3, respectively, in CH4 partial oxidation step with simultaneous high CO2 conversion (92%) in the CO2-splitting step at 850 °C. The results exemplify the feasibility to tailor the active lattice oxygen of perovskite by modulating the distortion of BO6 in ABO3, which ultimately influences their reaction performance in chemical looping processes.
TL;DR: Key steps for the promotion of this reaction by water are revealed when tuning the selectivity of a well-defined CeO2/Cu2O/Cu(111) catalyst from carbon monoxide and carbon dioxide to methanol under a reaction environment with methane, oxygen, and water.
Abstract: Highly selective oxidation of methane to methanol has long been challenging in catalysis. Here, we reveal key steps for the pro-motion of this reaction by water when tuning the selectivity of a well-defined CeO2/Cu2O/Cu(111) catalyst from carbon monoxide and carbon dioxide to methanol under a reaction environment with methane, oxygen, and water. Ambient-pressure x-ray photoelectron spectroscopy showed that water added to methane and oxygen led to surface methoxy groups and accelerated methanol production. These results were consistent with density functional theory calculations and kinetic Monte Carlo simulations, which showed that water preferentially dissociates over the active cerium ions at the CeO2-Cu2O/Cu(111) interface. The adsorbed hydroxyl species blocked O-O bond cleavage that would dehydrogenate methoxy groups to carbon monoxide and carbon dioxide, and it directly converted this species to methanol, while oxygen reoxidized the reduced surface. Water adsorption also displaced the produced methanol into the gas phase.
TL;DR: Density functional theory calculations revealed co-doping of W and Er tuned electronic structure of RuO2 by charge redistribution, which significantly prohibited formation of soluble Rux>4 and lowered adsorption energies for oxygen intermediates.
Abstract: Designing highly durable and active electrocatalysts applied in polymer electrolyte membrane (PEM) electrolyzer for the oxygen evolution reaction remains a grand challenge due to the high dissolution of catalysts in acidic electrolyte. Hindering formation of oxygen vacancies by tuning the electronic structure of catalysts to improve the durability and activity in acidic electrolyte was theoretically effective but rarely reported. Herein we demonstrated rationally tuning electronic structure of RuO2 with introducing W and Er, which significantly increased oxygen vacancy formation energy. The representative W0.2Er0.1Ru0.7O2-δ required a super-low overpotential of 168 mV (10 mA cm−2) accompanied with a record stability of 500 h in acidic electrolyte. More remarkably, it could operate steadily for 120 h (100 mA cm−2) in PEM device. Density functional theory calculations revealed co-doping of W and Er tuned electronic structure of RuO2 by charge redistribution, which significantly prohibited formation of soluble Rux>4 and lowered adsorption energies for oxygen intermediates. There is an increasing interest in understanding how defect chemistry can alter material reactivity. Here, authors tune the electronic structure of RuO2 by introducing W and Er dopants that boost acidic oxygen evolution performances by limiting oxygen vacancy formation during catalysis.
TL;DR: The results of XPS, Raman, H2-TPR, and DFT calculation all prove that the (310) facets possess the higher surface energy than other facets can feature the construction of oxygen vacancies, thus facilitating the adsorption and activate O3 into intermediate peroxide species and reactive oxygen species for eliminating adjacent CH3SH.
Abstract: The oxygen vacancy in MnO2 is normally proved as the reactive site for the catalytic ozonation, and acquiring a highly reactive crystal facet with abundant oxygen vacancy by facet engineering is advisable for boosting the catalytic activity. In this study, three facet-engineered α-MnO2 was prepared and successfully utilized for catalytic ozonation toward an odorous CH3SH. The as-synthesized 310-MnO2 exhibited superior activity in catalytic ozonation of CH3SH than that of 110-MnO2 and 100-MnO2, which could achieve 100% removal efficiency for 70 ppm of CH3SH within 20 min. The results of XPS, Raman, H2-TPR, and DFT calculation all prove that the (310) facets possess a higher surface energy than other facets can feature the construction of oxygen vacancies, thus facilitating the adsorption and activate O3 into intermediate peroxide species (O2-/O22-) and reactive oxygen species (•O2-/1O2) for eliminating adjacent CH3SH. In situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) revealed that the CH3SH molecular was chemisorbed on S atom to form CH3S-, which was further converted into intermediate CH3SO3- and finally oxidized into SO42- and CO32-/CO2 during the process. Attributed to the deep oxidation of CH3SH on 310-MnO2 via efficient cycling of active oxygen vacancies, the lifetime of 310-MnO2 can be extended to 2.5 h with limited loss of activity, while 110-MnO2 and 100-MnO2 were inactivated within 1 h. This study deepens the comprehension of facet-engineering in MnO2 and presents an efficient and portable catalyst to control odorous pollution.
TL;DR: The usage of dielectric polarization in surface coating to suppress the oxygen evolution of Li-rich material is reported, using Mg2 TiO4 as a proof of concept material and new insights into manipulating surface chemistry of electrode materials to control oxygen activity for high-energy-density rechargeable batteries are proposed.
Abstract: High-energy Li-rich layered cathode materials (≈900 Wh kg-1 ) suffer from severe capacity and voltage decay during cycling, which is associated with layered-to-spinel phase transition and oxygen redox reaction. Current efforts mainly focus on surface modification to suppress this unwanted structural transformation. However, the true challenge probably originates from the continuous oxygen release upon charging. Here, the usage of dielectric polarization in surface coating to suppress the oxygen evolution of Li-rich material is reported, using Mg2 TiO4 as a proof-of-concept material. The creation of a reverse electric field in surface layers effectively restrains the outward migration of bulk oxygen anions. Meanwhile, high oxygen-affinity elements of Mg and Ti well stabilize the surface oxygen of Li-rich material via enhancing the energy barrier for oxygen release reaction, verified by density functional theory simulation. Benefited from these, the modified Li-rich electrode exhibits an impressive cyclability with a high capacity retention of ≈81% even after 700 cycles at 2 C (≈0.5 A g-1 ), far superior to ≈44% of the unmodified counterpart. In addition, Mg2 TiO4 coating greatly mitigates the voltage decay of Li-rich material with the degradation rate reduced by ≈65%. This work proposes new insights into manipulating surface chemistry of electrode materials to control oxygen activity for high-energy-density rechargeable batteries.
TL;DR: In this paper, the degradation of the Fe-N-C structure and four times higher ORR activity loss when performing load cycling AST in O2-vs. Ar-saturated pH 1 electrolyte.
Abstract: Precious metal-free catalysts for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells are gaining momentum, with Fe-N-C catalysts comprising atomic FeN x sites the most promising candidate. Research and development is shifting from activity targets to improved stability of Fe-N-C catalysts in fuel cells. Their durability has hitherto been extensively studied using accelerated stress tests (AST) performed at room temperature and in inert-gas saturated acidic pH electrolyte. Here, we reveal stronger degradation of the Fe-N-C structure and four times higher ORR activity loss when performing load cycling AST in O2-vs. Ar-saturated pH 1 electrolyte. Raman spectroscopy results point towards strong carbon corrosion after AST in O2 , even when cycling at low potentials of 0.3-0.7 V vs. the reversible hydrogen electrode, while no corrosion occurred after any load cycling AST in Ar. The load cycling AST in O2 leads to the loss of a significant fraction of FeN x sites, as shown by energy dispersive X-ray spectroscopy analyses, and to the formation of Fe oxides. The results support that the unexpected carbon corrosion occurring at such low potential in the presence of O2 is due to reactive oxygen species produced between H 2 O 2 and Fe sites via Fenton reactions.
Journal Article•
TL;DR: The aim of the article was to review the current state of knowledge regarding oxidative stress, free radical function and free radical diseases using search engines such as PubMed and Google Scholar.
Abstract: Reactive oxygen species (ROS) are molecules capable of independent existence, containing at least one oxygen atom and one or more unpaired electrons. This group includes oxygen free radicals, e.g. superoxide anion radical, hydroxyl radical, hydroperoxyl radical, singlet oxygen, as well as free nitrogen radicals. Under physiological conditions, small quantities of ROS are formed during cell processes, such as aerobic respiration or inflammatory processes, mainly in hepatocytes and macrophages. Reactive oxygen species are primarily signalling molecules. In addition, they induce cell differentiation and apoptosis, thus contributing to the natural ageing process. They also participate in muscle contractions, regulation of vascular tone, and determine bactericidal and bacteriostatic activity. Increased production of free radicals is caused by excessive exposure to UV radiation, long-term stress conditions, intense physical exercise, improper diet and use of stimulants. Under physiological conditions, there is a balance between the generation and removal of free radicals from the body. The aim of the article was to review the current state of knowledge regarding oxidative stress, free radical function and free radical diseases. The search was performed using search engines such as PubMed and Google Scholar. The keywords used in the search included: oxygen radicals, oxidative stress, free radical-related diseases. Excessive formation of free radicals contributes to oxidative stress, causing damage at the molecular and cellular level. Reactive oxygen species in vitro cause chemical modifications as well as damaging effects to proteins (aggregation, denaturation), lipids (peroxidation), carbohydrates and nucleotides (changes in the DNA structure). These changes contribute to the development of many free radical-mediated diseases. Oxidative stress has a particularly adverse effect on the circulatory, respiratory and nervous systems.
TL;DR: In this paper, a Fe doped TiO2 catalyst (Fe-TiO2) was evaluated for NO oxidation reaction under visible light irradiation, and the results indicated that visible light benefited the adsorption and activation of NO at Fe sites (Fe-(NO)2) and Ti sites (Ti3+-NO) as well as the formation of active intermediates.
Abstract: A Fe doped TiO2 catalyst (Fe-TiO2) was evaluated for NO oxidation reaction under visible light irradiation. The Fe-TiO2 not only exhibited better catalytic activity and stability, but also suppressed the production of nitrogen dioxide (NO2) than the undoped TiO2. The results of in situ DRIFTS indicated that visible light benefited the adsorption and activation of NO at Fe sites (Fe-(NO)2) and Ti sites (Ti3+-NO) as well as the formation of active intermediates (e.g. Fe3+-NO3− and Ti4+-NO−). After EPR, DRS, PL and XPS testing, it was proposed that incorporating Fe ions into TiO2 induced the formation of more oxygen vacancies (OVs), while visible light further facilitated this process, resulting in an enhanced adsorption & activation of NO and also a promoted formation of reactive oxygen species (ROS). Thus, a strengthened photo-driven effect for oxidizing NO into NO2− and NO3− occurred on Fe-TiO2.
TL;DR: The results demonstrate that the adsorbed toluene can interact with oxygen species of catalyst to form physisorbed benzaldehyde, aldehydic adsorbate and benzoate species.
TL;DR: An In2O3 supported nickel catalyst has been prepared by wet chemical reduction with sodium borohydride (NaBH4) as a reducing agent for selective hydrogenation of carbon dioxide to methanol as mentioned in this paper.
TL;DR: In this article, a clean MnO2-Mn2O3 heterostructure interfaces were constructed by H+/KMnO4 treatment by using the T-05 catalyst.
Abstract: Mn-based heterostructure catalysts show great potential for catalytic oxidation of toluene owing to the unique properties of their hetero-interfaces Herein, we tailored the MnO2 heteroepitaxy over Mn2O3 to achieve well-defined morphology and constructed clean MnO2-Mn2O3 heterostructure interfaces by H+/KMnO4 treatment The T-05 catalyst (treating duration of 05 h) gave the highest activity and good stability The interface enhanced the reducibility and oxygen storage capacity compared with pure Mn2O3 Surface reconstruction and metastable facets exposure were observed after the H+/KMnO4 treatment, leading to the easy-release of lattice oxygen Additionally, abundant oxygen vacancies and redundant coordination lattice oxygen were observed at the MnO2 and Mn2O3 sides of the hetero-interface, respectively These features provided ample oxygen adspecies and increased lattice oxygen mobility The interface-related oxygen vacancies facilitated methyl dehydrogenation and demethylation of adsorbed toluene The redundant coordination lattice oxygen contributed to the enhanced aromatic ring breakage capability
TL;DR: The thermal vulnerability of high-voltage Li-ion batteries and the critical role of the surface fraction as a general mitigating approach are unveiled.
Abstract: The release of the lattice oxygen due to the thermal degradation of layered lithium transition metal oxides is one of the major safety concerns in Li-ion batteries. The oxygen release is generally ...
TL;DR: It is revealed that 0.2CoAl-LDH@CoSx is an efficient catalyst to activate PMS for SMX degradation, but also shed a novel insight into development of heterogeneous catalysts with oxygen vacancies.
TL;DR: In this article, LiNi0.80Co0.10O2 (NCM811) cathode material was studied in high voltage conditions (4.5"V and 4.7"V, respectively), and it was shown that the oxidation of lattice oxygen results in loss of oxygen through oxygen evolution and relative reactions between active oxygen evolution intermediates and electrolyte solvents.
TL;DR: In this article, abundant oxygen vacancies are injected into Co3O4 nanocrystals by controlling oxidation, and the hydrogen generation rate reaches up to 11,410mL min−min−1 min−1gCo−1 (313 K) owing to the presence of oxygen vacancies in Co 3O4.
Abstract: Highly active and robust non-noble metal catalysts are the key to large-scale application of hydrogen energy. In this article, abundant oxygen vacancies are injected into Co3O4 nanocrystals by controlling oxidation. These Co3O4 nanocrystals with oxygen vacancies are embedded into carbon nitride sheets. In the hydrolysis of ammonia borane, oxygen vacancies boost Co3O4 nanocrystalline catalyst to exhibit an outstanding catalytic activity. The hydrogen generation rate reaches up to 11,410 mL min−1 gCo−1 (313 K) owing to the presence of oxygen vacancies in Co3O4. In the stability tests, Co-CN-O-100 still maintains excellent catalytic activity with a specific rate of 9070 mL min−1 gCo−1 (80 %) after five cycles. The carbon nitride retards the growth of Co3O4 NCs and prevents active components from leaching. An oxygen vacancy-relating catalytic mechanism is proposed for the acceleration of rate-determining step of hydrolysis of ammonia borane according to a density functional theory simulation. This work makes a demonstration for the potential of oxygen vacancies in the development of energy catalysis.
TL;DR: In this article, the effects of the surface adsorbed oxygen species tuned by doping with different rare-metal metals (such as Ce, La, Sm and Y) on the catalytic behavior were elaborated systematically.
Abstract: During dry reforming of methane, oxygen species over the catalyst surface play an important role in CH4/CO2 reactivity, catalytic performance and carbon deposition. Herein, the effects of the surface adsorbed oxygen species tuned by doping with different rare-metal metals (such as Ce, La, Sm and Y) on the catalytic behavior were elaborated systematically. It was found that Y-doped catalyst exhibited the most amount of surface adsorbed oxygen species, followed by Sm, La, Ce and non-doped catalysts. The results confirmed that the surface adsorbed oxygen species were remarkably beneficial to enhance both CO2 activation and CH4 dissociation. Nevertheless, carbon formation and removal did not keep pace at low temperature due to more promotional effects of the surface adsorbed oxygen species on CH4 dissociation than CO2 activation. The gap between carbon deposition and removal was potential to be ameliorated through the accelerated activation to CO2 at high temperature.