Oxygen Species Research Articles

Study of the reactor temperature effect on H[formula omitted] production from steam decomposition using DBD plasma

Heat transfer data for the effect of the reactor and surrounding temperature on the hydrogen production from water vapour decomposition using Dielectric-Barrier Discharge (DBD) plasma are reported. The water vapour was injected into the plate micro channel reactor (PMCR) where the PMCR and its surrounding temperatures were raised using an insulated constant temperature heater type in a range of 20–130°C. This experiment was run at the following steam inlet conditions: pressure 100 kPa, temperature 300°C and flow rates of 100–200 ml/h, while the plasma applied voltage was in a range of 14–18 kV. In particular, the concentrations of hydrogen and oxygen species were analysed using gas phase chromatography (GC). It was observed that the hydrogen concentration percent increased with the reactor and surrounding temperature increased at all tested steam flow rates. Also, it was seen that the maximum obtained H2 concentrations were at high reactor temperature 130°C and plasma applied voltage of 18 kV. The effect of reactor temperature on the total heat transfer resistances at different steam flow rates was investigated. The trend behaviour of these resistances reveals interesting information about how these resistances interact and distribute according to the reactor heating temperature. Also, it was found that the total heat transfer rate decreased with the reactor temperature increased while the overall heat transfer rate increased with plasma voltage and reactor heating temperature. It can be concluded that the DBD plasma effect improved by decreasing the temperature difference between input steam and the PMCR temperatures. Further, it was clear that the steam dissociation processes not mainly depending on the plasma applied voltage but also the reactor heating temperature.

Effects of Cold Atmospheric Plasmas on Membranes

In a world of chemotherapeutic resistance, cold atmospheric plasmas (CAPs) have gained strong interest because they efficiently combat resistant bacterial infections and skin cancer without inducing serious side effects. CAPs are composed of electric fields, visible and UV-light, ionized gas and reactive nitrogen and oxygen species (RNOS), and can be delivered to any biological target because of their low heating capacity. Upon exposure of cells or tissues to plasma, the generated RNOS are solubilized in aqueous solution, where they target cell membranes, the natural barriers of cells.

Improved electrocatalytic activity of Pt supported onto Fe-doped TiO2 toward ethanol oxidation in acid media

The low stability of Pt-based catalysts due to severe corrosion of carbon support is one of the most critical technical issues hindering the widespread application of proton exchange membrane fuel cells. Here, we report the successful deposition of Pt nanoparticles on both pure titanium dioxide (TiO2) and Fe-doped TiO2 powder by chemical reduction using formic acid and their performance toward ethanol oxidation in acid media. First, the supported TiO2 was synthesized by the sol–gel method, and its physical-chemical properties were modified by the incorporation of iron (5.0 and 10.0 wt% Fe) into the structure of TiO2. The supports and catalysts were characterized by photoacoustic spectroscopy (PAS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The PAS data show that the doping of TiO2 with iron ions (III) decreases the band gap from 2.95 eV (undoped TiO2) to lower values depending on the iron content in the support (1.97 eV and 1.90 eV for 5Fe–TiO2 and 10Fe–TiO2, respectively). The XRD and TEM results indicate the presence of small-sized (around 3.5 nm) Pt nanostructures deposited onto the supports. The XPS analyses reveal surfaces rich in metallic Pt and oxygen species (O2− species, OH− and O atoms) in the vicinity of oxygen vacancies, as well as strong interactions between Pt nanoparticles and the Fe–TiO2 support. The Pt/Fe–TiO2 electrocatalyst exhibits higher catalytic activity toward ethanol oxidation than Pt/TiO2 and commercial Pt/C electrocatalysts (used as reference). The efficiency of Pt utilization increases with the Fe content. The sample with 10 wt% (mol/mol) of iron is then the most active catalyst. The enhanced activity and stability of the Pt/Fe–TiO2 catalyst can be attributed to the synergic and electronic effect of the compounds, Pt, and Fe–TiO2.

Catalytic reaction mechanism of formaldehyde oxidation by oxygen species over Pt/TiO2 catalyst

Theoretical calculations based on density functional theory (DFT) were employed to uncover the molecular-level oxidation mechanism of HCHO over Pt/TiO2 surface. All the three possible reaction mechanisms including Eley-Rideal mechanism, Langmuir-Hinshelwood mechanism and Mars-Van Krevelen mechanism were deeply investigated to determine the primary channel of HCHO oxidation on Pt/TiO2 catalyst. The adsorption energies and geometries show that HCHO and O2 are chemically adsorbed on Pt and Ti sites of the Pt/TiO2 catalyst surface, respectively. The adsorption energy of O2 (−141.91 kJ/mol) is higher than that of HCHO (−122.03 kJ/mol). HCHO oxidation reaction mainly occurs through the Eley-Rideal mechanism: gaseous HCHO reacts with activated O produced from the dissociation reaction of molecular oxygen on Pt/TiO2 surface by comparing the three possible mechanisms. HCHO oxidation reaction prefers the pathway of HCHO → H2CO2 → HCO2 → CO2. In the whole HCHO oxidation reaction, the elementary reaction of HCO2 dehydrogenation presents the highest activation energy barrier of 230.45 kJ/mol. Therefore, HCO2 dehydrogenation is recognized as the rate-determining step. The proposed skeletal reaction scheme can be used to well understand the microcosmic reaction process of HCHO oxidation on Pt/TiO2 catalyst.

Mixed silver-nickel oxide AgNiO2: Probing by CO during XPS study.

In this work, the reaction properties of mixed silver-nickel oxide AgNiO2 were investigated in the reaction of CO oxidation ranging from room temperature up to 350 °C. X-ray photoelectron spectroscopy revealed the presence of a single oxidized silver state and the combination of Ni2+ and Ni3+ species on the surface of the as-prepared mixed oxide. It was established that AgNiO2 was able to interact with CO at room temperature. It was accompanied by the simultaneous titration of the lattice (O2--like) and weakly charged (O--like) oxygen species. The interaction with CO below 100 °C resulted in the accumulation of carbonate-like species on the AgNiO2 surface. Above 150 °C, the surface structure of mixed oxide was found to be disrupted, resulting in the formation of individual particles of metallic silver and oxidized nickel.

Aerobic Oxidation of Fluorene to Fluorenone over Copper-Doped Co3O4 with a High Specific Surface Area

Copper-doped Co3O4 with a high specific surface area has been prepared by using mesoporous silica KIT-6 as a hard template, which showed exceptional catalytic performance (99% conversion of fluorene and 99% selectivity of fluorenone) for catalytic oxidation of fluorene to fluorenone using molecular oxygen as the oxidant in the absence of a radical initiator or other cocatalysts. Characterization results of N2 adsorption–desorption, X-ray diffraction, and transmission electron microscopy of the samples revealed the ordered mesoporous structure and increased specific surface area. X-ray photoelectron spectroscopy and O2 temperature-programmed desorption results showed the increased surface cobalt, Co3+/Co2+ ratio, and oxygen species. The H2 temperature-programmed reduction also indicated that the redox ability could be improved by doped copper in Co3O4, which all facilitated the aerobic oxidation reaction.

Pyridinecarboxylic Acid Derivative Stimulates Pro-Angiogenic Mediators by PI3K/AKT/mTOR and Inhibits Reactive Nitrogen and Oxygen Species and NF-κB Activation Through a PPARγ-Dependent Pathway in T. cruzi-Infected Macrophages.

Chagas disease is caused by Trypanosoma cruzi infection and represents an important public health concern in Latin America. Macrophages are one of the main infiltrating leukocytes in response to infection. Parasite persistence could trigger a sustained activation of these cells, contributing to the damage observed in this pathology, particularly in the heart. HP24, a pyridinecarboxylic acid derivative, is a new PPARγ ligand that exerts anti-inflammatory and pro-angiogenic effects. The aim of this work was to deepen the study of the mechanisms involved in the pro-angiogenic and anti-inflammatory effects of HP24 in T. cruzi-infected macrophages, which have not yet been elucidated. We show for the first time that HP24 increases expression of VEGF-A and eNOS through PI3K/AKT/mTOR and PPARγ pathways and that HP24 inhibits iNOS expression and NO release, a pro-inflammatory mediator, through PPARγ-dependent mechanisms. Furthermore, this study shows that HP24 modulates H2O2 production in a PPARγ-dependent manner. It is also demonstrated that this new PPARγ ligand inhibits the NF-κB pathway. HP24 inhibits IKK phosphorylation and IκB-α degradation, as well as p65 translocation to the nucleus in a PPARγ-dependent manner. In Chagas disease, both the sustained increment in pro-inflammatory mediators and microvascular abnormalities are crucial aspects for the generation of cardiac damage. Elucidating the mechanism of action of new PPARγ ligands is highly attractive, given the fact that it can be used as an adjuvant therapy, particularly in the case of Chagas disease in which inflammation and tissue remodeling play an important role in the pathophysiology of this disease.

Cycles of Nitric Oxide (NO), Superoxide Radical Anion (• O2 - ) and Hydrogen Sulfur/Sulfur Dioxide (H2 S/SO2 ) in Mammals

Abstract The article analyzes the Cyclicity Principle, together with the atomic principle of the structure of matter and the holographic principle. According to the developed concepts, the above principles make it possible to answer the question: how nature is unified, and how living organisms ensure the regulation and stabilization of nitric oxide (NO), superoxide anion-radical (•O2-) and hydrogen sulfide/sulfur dioxide (H2S/SO2), involved in intra- and intercellular signaling in mammals. Keywords Atomic Principle of the Structure of Matter; Cyclic Principle; Holographic Principle; Hydrogen Sulfide/Sulfur Dioxide Cycle; Nitric Oxide Cycle; Regulation of the Content of Reactive Nitrogen and Oxygen Species; Superoxide Anion-Radical Cycle

Fast and low-cost evaluation of hydroxykynurenine activity

The enzyme 3-hydroxykynurenine transaminase (HKT) acts as an important enzyme in tryptophan catabolism of disease-carrier insects, e.g. Aedes aegypti and Anopheles gambiae. HKT is a detoxification enzyme that converts 3-hydroxykynurenine (a precursor for reactive nitrogen and oxygen species) into xanthurenic acid (stable and nontoxic compound). We have previously synthesized eleven new oxadiazole derivatives and demonstrated their noncompetitive inhibitory activity towards HKT from A. aegypti (https://doi.org/10.1016/j.bmc.2019.115252). These findings are presented in a research paper accompanying the present technical report on a new assay to overcome the fact that the substrate and product of the HKT-catalyzed reaction exhibit maximum absorption at very near wavelength (370 and 369 nm, respectively). The methods previously described in the literature rely on chromatographic separation prior to absorbance quantification, which limits their use for inhibitor screening. Due to HKT attractive features as a molecular target for larvicidal compounds, we report herein a new, faster and affordable methodology to evaluate the enzymatic activity of recombinant HKT, and therefore allow for the fast screening of potential HKT inhibitors via absorbance spectrophotometer. The advantages of the proposed methodology to previously described ones are:•It is faster and cheaper than HPLC-based assays because it does not require the use of chromatography columns and solvents to separate reaction components;•It uses of 96-well plates, enabling the simultaneous quantification of samples;•It can be applied to all transaminases that have xanthurenic acid as a product.

Configuration of gradient-porous ultrathin FeCo2S4 nanosheets vertically aligned on Ni foam as a noncarbonaceous freestanding oxygen electrode for lithium-oxygen batteries.

The degradation of oxygen electrodes caused by oxygen species in lithium-oxygen (Li-O2) batteries deteriorates their energy efficiency and cyclability and seriously hinders their commercial application. To achieve high energy efficiency and long-term cycle life, gradient-porous ultrathin FeCo2S4 nanosheets on Ni foam (FeCo2S4@Ni) were deliberately designed as a noncarbonaceous freestanding oxygen electrode for Li-O2 batteries. Notably, the gradient-porous structure in FeCo2S4@Ni can offer sufficient active sites as well as mitigate polarization caused by the mass transfer during discharge and charge. The synergistic effect of the two transition metals, Fe2+ and Co3+, optimizes their d-band electronic structure and enhances the intrinsic activity of the oxygen electrode. Benefiting from the above merits, the FeCo2S4@Ni based Li-O2 battery demonstrates greatly increased discharge capacity (8001 mA h g-1), improved rate capability (with a high capacity of 4401 mA h g-1 at 500 mA g-1), and enhanced cycling stability (with a low overpotential of below 1 V after 109 cycles). Our work demonstrates that the battery performance can be improved by regulating the structure and composition of the oxygen electrode and provides a promising strategy for developing high performance Li-O2 batteries.

Age-induced NLRP3 Inflammasome Over-activation Increases Lethality of SARS-CoV-2 Pneumonia in Elderly Patients.

Age is one of the most important prognostic factors associated to lethality in SARS-CoV-2 infection. In multivariate analysis, advanced age was an independent risk factor for death. Recent studies suggest a role for the nucleotide-binding domain and leucine rich repeat containing family, pyrin domain containing 3 (NLRP3) inflammasome activation in lung inflammation and fibrosis in SARS-CoV and SARS-CoV-2 infections. Increased NLRP3/ apoptosis-associated speck-like protein (ASC) mRNA expression and increased caspase-1 activity, have been observed in aged lung, provoking increased and heightened expression levels of mature Interleukin (IL)-1β and IL-18 in aged individuals. Aged individuals have a basal predisposition to over-react to infection, displaying an increased hyper-inflammatory cascade, that seems not to be fully physiologically controlled. NLRP3 inflammasome is over-activated in aged individuals, through deficient mitochondrial functioning, increased mitochondrial Reactive Oxigen Species (mtROS) and/or mitochondrial (mt)DNA, leading to a hyper-response of classically activated macrophages and subsequent increases in IL-1 β. This NLRP3 over-activated status in elderly individuals, is also observed in telomere dysfunctional mice models. In our opinion, the NLRP3 inflammasome plays a central role in the increased lethality observed in elderly patients infected by COVID-19. Strategies blocking inflammasome would deserve to be studied.

Effective low‐temperature catalytic abatement of benzene over porous Mn‐Ni composite oxides synthesized via the oxalate route

AbstractBACKGROUNDBenzene (C6H6) is a typical kind of volatile organic compound (VOC) which can exert great harm to both human health and the environment, and, thus, which needs to be eliminated before its emission. In this work, porous manganese–nickel (Mn‐Ni) composite oxide catalysts were synthesized through the oxalate route and applied to thermal catalytic oxidation of C6H6. By means of activity tests and relative physico‐chemical characterizations, the factors affecting the activity of those Mn‐Ni composite oxides were explored.RESULTSNitrogen (N2)‐adsorption/desorption and X‐ray photoelectron spectroscopy (XPS) measurements indicated that the Brunauer–Elmett–Teller (BET) surface area and the content of surface‐adsorbed oxygen species were increased due to the addition of Ni into Mn oxide (MnOx). Meanwhile, the oxygen mobility and reducibility also were improved in the Mn‐Ni composite oxides. Accordingly, compared with MnOx, the Mn‐Ni catalysts showed higher activity for thermal catalytic oxidation of C6H6. Moreover, porous Mn‐Ni composite oxides with a Mn:Ni molar ratio of 4:1 (Mn4Ni1) displayed the best catalytic activity. Further investigation indicated that the excellent catalytic performance of Mn4Ni1 composite oxides could be ascribed mainly to the larger BET surface area and the richer content of surface‐adsorbed oxygen species, as well as stronger oxygen mobility and better reducibility compared with other Mn‐Ni catalysts.CONCLUSIONSThe Mn4Ni1 composite oxides showed a lowest T90 value of 172 °C (C6H6 concentration 200 ppm, WHSV 60 000 mL g−1 h−1) among all of the obtained Mn‐Ni composite oxides. Moreover, it also exhibited favourable catalytic stability at 210 °C in the presence or absence of moisture. © 2019 Society of Chemical Industry

Catalytic Hydrodeoxygenation of Fast Pyrolysis Bio-Oil from Saccharina japonica Alga for Bio-Oil Upgrading

Biomass conversion via pyrolysis has been regarded as a promising solution for bio-oil production. Compared to fossil fuels, however, the pyrolysis bio-oils from biomass are corrosive and unstable due to relatively high oxygen content. Thus, an upgrading of bio-oil is required to reduce O component while improving stability in order to use it directly as fuel sources or in industrial processes for synthesizing chemicals. The catalytic hydrodeoxygenation (HDO) is considered as one of the promising methods for upgrading pyrolysis bio-oil. In this research, the HDO was studied for various catalysts (HZSM-5, metal, and metal-phosphide catalysts) to improve the quality of bio-oil produced by fast pyrolysis of Saccharina japonica (SJ) in a fluidized-bed reactor. The HDO processing was carried out in an autoclave at 350 °C and different initial pressures (3, 6, and 15 bar). During HDO, the oxygen species in the bio-oil was removed primarily via formation of CO2 and H2O. Among the gases produced through HDO, CO2 was observed to be most abundant. The C/O ratio of produced bio-oil increased when CoMoP/γ-Al2O3, Co/γ-Al2O3, Fe/γ-Al2O3, or HZSM-5 was used. The Co/γ-Al2O3 resulted in higher HDO performance than other catalysts. The bio-oil upgraded with Co/γ-Al2O3 showed high HHV (34.41 MJ/kg). With the use of catalysts, the kerosene-diesel fraction (carbon number C12–C14) was increased from 36.17 to 38.62–48.92 wt.%.

Hydrogen Evolution on Nano-StructuredCuO/Pd Electrode: Raman Scattering Study

In this study, the processes taking place on the surfaces of nanostructured Cu/CuO and Cu/CuO/Pd electrodes at different potential, E, values in the solutions of 0.1 M KOH in H 2 O and D 2 O (heavy water) were probed by surface enhanced Raman spectroscopy (SERS), and the analysis of electrochemical reactions occurring under experimental conditions is presented. The bands of the SERS spectra of the Cu/CuO/Pd electrode observed in the range of E values from +0.3 V to 0 V (standard hydrogen electrode (SHE)) at 1328–1569 cm − 1 are consistent with the existence of species that are adsorbed or weakly bound to the surface with the energy of interaction close to 15–21 kJ mol − 1 . These bands can be attributed to the ad(ab)sorbed (H 3 O + ) ad , (H 2 + ) ab , and (H 2 + ) ad ions as intermediates in reversible hydrogen evolution and oxidation reactions (HER/HOR) taking place on the Cu/CuO/Pd electrode. There was no isotopic effect observed; this is consistent with the dipole nature of the electron-ion pair formation of adsorbed (H 3 O + ) ad and (H 2 + ) ad or (D 3 O + ) ad and (D 2 + ) ad . In accordance with the literature data, SERS bands at 125–146 cm − 1 and ∼520–565 cm − 1 were assigned to Cu(I) and Cu(II) oxygen species. These findings corroborate the quantitative stepwise mechanism of water reduction.

Simulated air dives induce superoxide, nitric oxide, peroxynitrite, and Ca2+ alterations in endothelial cells.

Human diving is known to induce endothelial dysfunction. The aim of this study was to decipher the mechanism of ROS production during diving through the measure of mitochondrial calcium concentration, peroxynitrite, NO°, and superoxide towards better understanding of dive-induced endothelial dysfunction. Air diving simulation using bovine arterial endothelial cells (compression rate 101 kPa/min to 808 kPa, time at depth 45 min) was performed in a system allowing real-time fluorescent measurement. During compression, the cells showed increased mitochondrial superoxide, peroxynitrite, and mitochondrial calcium, and decreased NO° concentration. MnTBAP (peroxynitrite scavenger) suppressed superoxide, recovered NO° production and promoted stronger calcium influx. Superoxide and peroxynitrite were inhibited by L-NIO (eNOS inhibitor), but were further increased by spermine-NONOate (NO° donor). L-NIO induced stronger calcium influx than spermine-NONOate or simple diving. The superoxide and peroxynitrite were also inhibited by ruthenium red (blocker of mitochondrial Ca2+ uniporter), but were increased by CGP (an inhibitor of mitochondrial Na+-Ca2+ exchange). Reactive oxygen and nitrogen species changes are associated, together with calcium mitochondrial storage, with endothelial cell dysfunction during simulated diving. Peroxynitrite is involved in NO° loss, possibly through the attenuation of eNOS and by increasing superoxide which combines with NO° and forms more peroxynitrite. In the field of diving physiology, this study is the first to unveil a part of the cellular mechanisms of ROS production during diving and confirms that diving-induced loss of NO° is linked to superoxide and peroxynitrite.

Ruthenium thin film under methanation atmosphere analyzed by x-ray photoelectron spectroscopy

Ruthenium thin films were prepared by DC magnetron sputtering on silicon (111) substrates. Samples were subjected to different temperature conditions (300, 400, 500, and 600 °C) under a flow of hydrogen and carbon dioxide with a 4:1 molar ratio to emulate the atmosphere of the methanation reaction. Each treatment was performed in situ. X-ray photoelectron spectroscopy was used to examine the surface chemical changes on Ru thin films before and after the treatments. Survey spectra, Ru 3d, and O 1s core level spectra were measured for each sample. Results showed that the O 1s spectra presented significant changes in all samples; before the thermal treatments, this signal has four different oxygen species, where it can be appreciated the existence of nonstoichiometric oxidized ruthenium. The latter disappears after the first heat treatment due to the high reducibility of ruthenium. Subsequently, in the following treatments, ruthenium oxide reappears, in smaller quantities when compared with the film without treatments. However, the highest amount of oxidized ruthenium can be observed in the temperature range (400–500 °C) during the treatments, in which the conversion of CO2 is maximum for Ru supported catalysts.

Study on Chemical Modifications of Glutathione by Cold Atmospheric Pressure Plasma (Cap) Operated in Air in the Presence of Fe(II) and Fe(III) Complexes

Cold atmospheric pressure plasma is an attractive new research area in clinical trials to treat skin diseases. However, the principles of plasma modification of biomolecules in aqueous solutions remain elusive. It is intriguing how reactive oxygen and nitrogen species (RONS) produced by plasma interact on a molecular level in a biological environment. Previously, we identified the chemical effects of dielectric barrier discharges (DBD) on the glutathione (GSH) and glutathione disulphide (GSSG) molecules as the most important redox pair in organisms responsible for detoxification of intracellular reactive species. However, in the human body there are also present redox-active metals such as iron, which is the most abundant transition metal in healthy humans. In the present study, the time-dependent chemical modifications on GSH and GSSG in the presence of iron(II) and iron(III) complexes caused by a dielectric barrier discharge (DBD) under ambient conditions were investigated by IR spectroscopy, mass spectrometry and High Performance Liquid Chromatography (HPLC). HPLC chromatograms revealed one clean peak after treatment of both GSH and GSSH with the dielectric barrier discharge (DBD) plasma, which corresponded to glutathione sulfonic acid GSO3H. The ESI-MS measurements confirmed the presence of glutathione sulfonic acid. In our experiments, involving either iron(II) or iron(III) complexes, glutathione sulfonic acid GSO3H appeared as the main oxidation product. This is in sharp contrast to GSH/GSSG treatment with DBD plasma in the absence of metal ions, which gave a wild mixture of products. Also interesting, no nitrosylation of GSH/GSSG was oberved in the presence of iron complexes, which seems to indicate a preferential oxygen activation chemistry by this transition metal ion.

Retarding graphitization of soft carbon precursor: From fusion-state to solid-state carbonization

The soft carbon precursor pitch, featured with low-cost and easy-availability, is regarded as a very promising candidate for the synthesis of carbonaceous anode. However, the Na-storage performance of pitch-derived carbon is strongly hindered by its highly graphitized structure, which mainly comes from the reordering during the fusion-state carbonization. To prevent the graphitization, herein, we propose an in-situ Mg(NO3)2·6H2O solidification strategy to convert the fusion-state to solid-state carbonization. The oxygen species and solid products generated from the decomposition of Mg(NO3)2·6H2O can retard the melting and reordering of pitch, thus tailoring the microstructure. The optimal sample displays outstanding overall performances in both half- and full-cells, with ~3-fold increase in capacity. Particularly, the carbon yield is significantly increased from 61% to 92% because less organic molecules can escape. The understandings gained in this work not only offer insights to adjust the carbonization process, but also provide solutions to obtain highly disordered carbon anodes from soft carbon precursors.

Yolk-shell-like mesoporous CoCrOx with superior activity and chlorine resistance in dichloromethane destruction

Promoting chlorine resistance and inhibiting by-product generation are critical issues in catalytic destruction of chlorinated volatile organic compounds (CVOCs). Herein, a yolk-shell-like mesoporous CoCrOx as a robust catalyst was synthesized for deep destruction of dichloromethane (DCM) considering its superior mass transfer and molecule enrichment ability. The strong interaction between Co and Cr elements in CoCrOx results in efficient generation of active Cr6+ and oxygen species, which greatly enhances the activity of CoCrOx in DCM oxidation, much higher than that of Co3O4, Co3O4+Cr2O3 and Cr2O3. Chloromethane (CH3Cl), trichloromethane (CHCl3) and tetrachloromethane (CCl4) can be detected as the cleavage of CH bond and generation of C-Cl bond during DCM destruction. We found that the acid sites can effectively inhibit the formation of by-products over CoCrOx material, which is a promising material for CVOC elimination. The results from this work provide some new insights into the design of catalysts for CVOC destruction.

Tailoring the structure of supported δ-MnO2 nanosheets to raise pseudocapacitance by surface-modified carbon cloth

Coupling electrode composed of carbonaceous materials and metal oxides can effectively raise pseudocapacitance; however, due to the weak interaction between carbonaceous materials and metal oxides, structural control of the resultant coupling electrode remains a great challenge. Herein, surface-modified carbon cloth (SMCC), which is obtained by carbonizing the hydrothermal products of cetyltrimethylammonium bromide and glucose solution on carbon cloth (CC), is employed to regulate in-situ growth of δ-MnO2 in a KMnO4 and H2SO4 solution at hydrothermal condition. Structural characterizations indicate that surface modification renders SMCC to possess an oxygen-species-rich superhydrophilic surface, which in turn enables the supported δ-MnO2 to form the dense ultrathin nanosheets and abundant oxygen-vacancy (Vo) structure. Electrochemical tests demonstrate that the MnO2/SMCC can exhibit a specific capacitance of 508 F g−1 (792.5 C g−1) at 1 A g−1 under working potential range from −0.3 to 1.26 VAg/AgCl in three-electrode system, outperforming previously-reported δ-MnO2-based materials. Further, the detailed structural investigations identify that the oxygen species on SMCC dominate the generation of Vo in δ-MnO2 by reducing thickness and interface bonding, and the Vo in δ-MnO2 improves the pesudocapacitance by promoting the transition of Mn2+ to Mn4+.