In recent decade, Au nanoclusters of atomic precision （AunLm, where L= organic ligand： thiolate andphosphine） have been shown as a new promising nanogold catalyst. The well-defined AunLm catalystspossess unique ele...In recent decade, Au nanoclusters of atomic precision （AunLm, where L= organic ligand： thiolate andphosphine） have been shown as a new promising nanogold catalyst. The well-defined AunLm catalystspossess unique electronic properties and frameworks, providing an excellent opportunity to correlate theintrinsic catalytic behavior with the cluster＇s framework as well as to study the catalytic mechanismsover gold nanoclusters. In this review, we only demonstrate the important roles of the gold nanoclustersin the oxygen activation （e.g., 302 to 102） and their selective oxidations in the presence of oxygen （e.g., COto C02, sulfides to sulfoxides, alcohol to aldehyde, styrene to styrene epoxide, amines to imines, andglucose to gluconic acid）. The size-specificity （Au25 （1.3 nm）, Au38 （].5 nm）, Au144 （1.9 nm）, etc.）, ligandengineering （e.g., aromatic vs aliphatic）, and doping effects （e.g., copper, silver, palladium, and platinum）are discussed in details. Finally, the proposed reactions＇ mechanism and the relationships of clusters＇structure and activity at the atomic level also are presented.展开更多
The apparent sulfur oxidation activities of four pure thermophilic archaea, Acidianus brierleyi （JCM 8954）, Metallosphaera sedula （YN 23）, Acidianus manzaensis （YN 25） and Sulfolobus metallicus （YN 24） and the...The apparent sulfur oxidation activities of four pure thermophilic archaea, Acidianus brierleyi （JCM 8954）, Metallosphaera sedula （YN 23）, Acidianus manzaensis （YN 25） and Sulfolobus metallicus （YN 24） and their mixture in bioleaching chalcopyrite were compared, which were characterized indirectly by the evolution of the cells concentration, pH value and sulfate ions concentration in solution. The results show that the mixed culture contributed significantly to the raising of leaching rate, which suggests that the mixed culture had a higher sulfur oxidation activity than the pure culture. Meanwhile, the results also indicate that the changes of parameters characterizing the sulfur oxidation activity of thermophilic archaea are often influenced by many factors, so it is hard to reflect accurately the specific sulfur oxidation activities among the different sulfur-oxidizing microbes when bioleaching chalcopyrite at different conditions. Accordingly, an efficient method to characterize microbial sulfur oxidation activity appears to be desirable.展开更多
Polycrystalline SnO2 fine powder consisting of nano-particles （SnO2-NP）, SnO2 nano-sheets （SnO2-NS）, and SnO2 containing both nano-rods and nano-particles （SnO2-NR＋NP） were prepared and used for CO oxidation. S...Polycrystalline SnO2 fine powder consisting of nano-particles （SnO2-NP）, SnO2 nano-sheets （SnO2-NS）, and SnO2 containing both nano-rods and nano-particles （SnO2-NR＋NP） were prepared and used for CO oxidation. SnO2-NS possesses a mesoporous structure and has a higher surface area, larger pore volume, and more active species than SnO2-NP, and shows improved activity. In contrast, although SnO2-NR＋NP has only a slightly higher surface area and pore volume, and slightly more active surface oxygen species than SnO2-NP, it has more exposed active （110） facets, which is the reason for its improved oxidation activity. Water vapor has only a reversible and weak influence on SnO2-NS, therefore it is a potential catalyst for emission control processes.展开更多
The effects of chloride anion （Cl-） （up to 1.0 mol/L） on the decolorization of a model compound,azo dye Acid Orange 7 （AO7）,by sulfate radical （SO4-） based-peroxydisulfate （PS） or peroxymonosulfate （PMS） o...The effects of chloride anion （Cl-） （up to 1.0 mol/L） on the decolorization of a model compound,azo dye Acid Orange 7 （AO7）,by sulfate radical （SO4-） based-peroxydisulfate （PS） or peroxymonosulfate （PMS） oxidation under various activated conditions （UV 254 nm /PS,Thermal （70°C/PS,UV 254 nm /PMS,Co 2＋ /PMS） were investigated.Methanol and NH4 ＋ were used as quenching reagents to determine the contributions of active chlorine species （dichloride radical （Cl2-.） and hypochlorous acid （HClO））.The results indicated that the effects of Cl- on the reaction mechanism were different under various activated conditions.For UV/PS and Thermal/PS,the inhibition tendency became more clear as the Cl- concentration increased,probably due to the reaction between Cl- and SO4-.and the generation of Cl2-.or HClO.For UV/PMS,Cl- did not exhibit inhibition when the concentration was below 0.1 mol/L.As Cl- concentration reached to 1.0 mol/L,the decolorization rate of AO7 was,however,accelerated,possibly because PMS directly reacts with Cl- to form HClO.For Co2＋ /PMS,Cl- exhibited a significant inhibiting effect even at low concentration （ 0.01 mol/L）.When Cl- concentration exceeded 0.1 mol/L,the activation of PMS by Co 2＋ was almost completely inhibited.Under this condition,HClO maybe played a major role in decolorization of AO7.The results implicated that chloride ion is an important factor in SO4-.-based degradation of organic contamination in chloride-containing water.展开更多
The microstructural evolution and oxidation resistance of multi-walled carbon nanotubes （MWCNTs） by di- rectly heating silicon powder and MWCNTs in a coke bed from 1000 to 1500 ~C are investigated with the aid of X-...The microstructural evolution and oxidation resistance of multi-walled carbon nanotubes （MWCNTs） by di- rectly heating silicon powder and MWCNTs in a coke bed from 1000 to 1500 ~C are investigated with the aid of X-ray diffraction （XRD）, scanning electron microscopy （SEM）, high resolution transmission electron microscopy （HRTEM） and thermogravimetry-differential scanning calorimetry （TG-DSC）. The results showed that the morphology and microstructure of MWCNTs did not change much after being treated from 1000 ~C to 1200 ~C. An obvious SiC coating was formed on the surface of MWCNTs from 1300 to 1400 ~C. Up to 1500 ~C, nearly all the MWCNTs transformed into SiC nanowires. The oxidation resistance of the treated MWCNTs was improved compared with as-received ones. Non-isothermal kinetics showed that the oxidation activation energy of the treated MWCNTs reached 208 kJ/mol, much higher than 264 k J/tool of as-received ones.展开更多
Hydroxyl radicals(·OH) generated on anode play a vital role in electrochemical oxidation(EO) of organic pollutants for water treatment. Inspired by the four-electron oxygen evolution reaction(OER), we supposed an...Hydroxyl radicals(·OH) generated on anode play a vital role in electrochemical oxidation(EO) of organic pollutants for water treatment. Inspired by the four-electron oxygen evolution reaction(OER), we supposed an anode-selection strategy to stabilize deeply oxidized states(*O and*OOH) which are beneficial to generating·OH. To verify the hypothesis, a candidate anode component(MIL-101(Cr), a well-known metal-organic framework with active variable-valence transition metal centers) was used to coat Ti/TiO_(2)plate to fabricate anodes. Compared to TiO_(2)(101) plane on undecorated anode surface, fast and complete removal of aniline and phenol, and improved energy utilization were achieved on MIL-101(Cr)-coatedTi/TiO_(2)anode. Mechanism investigation, including pollutant degradation pathways, showed the predominate contribution(69.60%–75.13%) of·OH in pollutant mineralization. Density functional theory(DFT)computations indicated Cr site in MIL-101(Cr) was more conducive to stabilizing*O and*OOH, leading to thermodynamical spontaneous generation of·OH. This work opens up an exciting avenue to explore·OH production, and supplies a useful guidance to the development of anode materials for EO process.展开更多
MnO_x-CeO_2 catalysts were synthesized to investigate the active sites for NO oxidation by varying the calcination temperature. XRD and TEM results showed that cubic CeO_2 and amorphous MnO_x existed in MnO_x-CeO_2 ca...MnO_x-CeO_2 catalysts were synthesized to investigate the active sites for NO oxidation by varying the calcination temperature. XRD and TEM results showed that cubic CeO_2 and amorphous MnO_x existed in MnO_x-CeO_2 catalysts. High temperature calcination caused the sintering of amorphous MnO_x and transforming to bulk crystalline Mn_2O_3, H_2-TPR and XPS results suggested the valence of Mn in MnO_x-CeO_2 was higher than pure MnO_x, and decreased with the increasing calcination temperature, The turnover frequency（TOF） was calculated based on the initial reducibility according to H_2-TPR quantitation and kinetic study. The TOF results indicated that the initial reducibility of amorphous MnO_x with high valence manganese ions was equivalent to the active sites for NO oxidation. It can be inferred that the amorphous MnO_x plays a key role in low-temperature NO oxidation.展开更多
The oxidation kinetics and composition of oxide scales on low carbon steel （SPHC） were studied during i- sothermal oxidation. Thermogravimetric analyzer （TGA） was used to simulate isothermal oxidation process of S...The oxidation kinetics and composition of oxide scales on low carbon steel （SPHC） were studied during i- sothermal oxidation. Thermogravimetric analyzer （TGA） was used to simulate isothermal oxidation process of SPHC for 240 min under air condition, and the temperature range was from 500 to 900 ℃. Scanning electron microscope （SEM） was used to observe cross-sectional scale morphology and analyze composition distribution of oxide scales. The morphology of oxide scale was classical three-layer structure. Fe2 03 developed as whiskers at the outermost lay- er, and interlayer was perforated-plate Fe3 04 while innermost layer was pyramidal FeO. From the oxidation curves, the oxidation mass gain per unit area with time was of parabolic relation and oxidation rate slowed down. On the ba- sis of experimental data, the isothermal oxidation kinetics model was derived and oxidation activation energy of SPHC steel was 127. 416 kJ/mol calculated from kinetics data.展开更多
Bioleaching of sulfide minerals by bacteria, mainly Thiobacillus ferrooxidans(T.f.) and Thiobacillus thiooxidans, plays an important role in hydrometallurgy because of its economic and environmental attractions. The s...Bioleaching of sulfide minerals by bacteria, mainly Thiobacillus ferrooxidans(T.f.) and Thiobacillus thiooxidans, plays an important role in hydrometallurgy because of its economic and environmental attractions. The surveys of production process and the bacterial oxidation activity in the heap bioleaching were investigated. The results show that pH value is high, bacteria biomass and ferric concentration are low, generation time (above 7.13 h) is long in leachate, and less bacteria are adsorbed on the ores. The bacteria in the leachate exposing on the surface and connecting with mineral, have much faster oxidation rate of Fe(Ⅱ) and shorter generation time, compared with those which are in the reservoir for a long time. There is diversity for oxidation activity of Fe(Ⅱ), while there is no diversity for oxidation of sulfur. So it is advisable to add sulfuric acid to degrade pH value to 2.0, add nutrients and shorten recycling time of leachate, so as to enhance bacteria concentration of leachate and the leaching efficiency.展开更多
Ozonation of oxalate in aqueous phase was performed with a commercial activated carbon（AC）in this work. The effect of AC dosage and solution pH on the contribution of hydroxyl radicals（HOU） in bulk solution and ox...Ozonation of oxalate in aqueous phase was performed with a commercial activated carbon（AC）in this work. The effect of AC dosage and solution pH on the contribution of hydroxyl radicals（HOU） in bulk solution and oxidation on the AC surface to the removal of oxalate was studied. We found that the removal of oxalate was reduced by tert-butyl alcohol（tBA） with low dosages of AC,while it was hardly affected by tBA when the AC dosage was greater than 0.3 g/L. tBA also inhibited ozone decomposition when the AC dosage was no more than 0.05 g/L, but it did not work when the AC dosage was no less than 0.1 g/L. These observations indicate that HOUin bulk solution and oxidation on the AC surface both contribute to the removal of oxalate. HOU oxidation in bulk solution is significant when the dosage of AC is low, whereas surface oxidation is dominant when the dosage of AC is high. The oxalate removal decreased with increasing pH of the solution with an AC dosage of 0.5 g/L. The degradation of oxalate occurs mainly through surface oxidation in acid and neutral solution, but through HOUoxidation in basic bulk solution. A mechanism involving both HOUoxidation in bulk solution and surface oxidation was proposed for AC enhanced ozonation of oxalate.展开更多
This study was focused on the influence of active oxygen on the performance of Pt/CeO2 catalysts for CO oxidation. A series of CeO2 supports with different contents of active oxygen were obtained by adding surfactant ...This study was focused on the influence of active oxygen on the performance of Pt/CeO2 catalysts for CO oxidation. A series of CeO2 supports with different contents of active oxygen were obtained by adding surfactant at different synthesis steps. 0.25 wt% Pt was loaded on these CeO2 supports by incipientwetness impregnation methods. The catalysts were characterized by N2 adsorption, X-ray diffraction（XRD）, high-resolution transmission electron microscopy（HRTEM）, H2 temperature-programmed reduction（H2-TPR）, dynamic oxygen storage capacity（DOSC） and in-situ DRIFTS technologies. For S-f supports, the surfactant was added into the solution before spray-drying in the synthesis process, which facilitates more active oxygen formation on the surface of CeO2. After loading Pt, the more active oxygen on CeO2 contributes to dispersing Pt species and enhancing the CO oxidation activity. As for the aged samples,Pt-R-h shows the highest activity above 190 ℃ because of the presence of more partly oxidized Pt^（δ＋） species. Thus the activity is also influenced by the states of Pt and the Pt^（δ＋） species may contribute to the high activity at elevated temperature.展开更多
Pd@Zr/Ce O2 core-shell catalyst prepared by hydrothermal method was applied in CO oxidation reaction, exhibiting high CO oxidation activity at low temperature.XRD（X-ray diffraction） analysis demonstrated that the re...Pd@Zr/Ce O2 core-shell catalyst prepared by hydrothermal method was applied in CO oxidation reaction, exhibiting high CO oxidation activity at low temperature.XRD（X-ray diffraction） analysis demonstrated that the remarkable enhancement of catalytic performance was found to depend on the presence of more oxygen vacancies in the core-shell structure, which contributed higher content of and ready release of active oxygen species at low temperature, confirmed by H2-TPR（temperature programed reduction） results.Interestingly, introducing a small amount of zirconium（0.5 wt.%） exhibited a significant improvement of catalytic activity because the introduction of Zr further improved the amount of crystal defects and promoted the migration of oxygen species.展开更多
The oxidation of lignite and bituminous coal samples modified by 5 wt%(in terms of dry salt)addition of copper salts Cu(NO_(3))_(2),CuSO_(4),and Cu(CH_(3)COO)_(2) was studied.The samples’reactivity was studied by the...The oxidation of lignite and bituminous coal samples modified by 5 wt%(in terms of dry salt)addition of copper salts Cu(NO_(3))_(2),CuSO_(4),and Cu(CH_(3)COO)_(2) was studied.The samples’reactivity was studied by thermogravimetry within a temperature range of 45–600℃ at a heating rate of 2.5℃/min in an oxidizing environment.The introduction of activating additives has resulted in a significant decrease in the temperature of intense oxidation onset(ΔT_(i)=20/94℃),in a reduction in the sample residence time in the volatile matter release region(Δt_(e)=2/22 min)and the total duration of the coal combustible mass oxidation(Δt_(f)=8/14 min).The Friedman method was used to calculate the activation energy values for the oxidation process of the modified samples.The maximum change in activation energy values was observed for the bituminous coal sample.The possible mechanism behind the action of the copper-salt additives,which activate the oxidation of lignite and bituminous coal,is discussed.According to the data of mass spectrometric analysis,the concentration of NOx in the reaction products decreases as the temperature of the activated oxidation process is shifted towards the low-temperature region.展开更多
There are two theories regarding the origin of the remarkable synergistic effect observed in Au‐Ag bimetallic catalysts when applied to various oxidative reactions. One is based on the importance of the contact inter...There are two theories regarding the origin of the remarkable synergistic effect observed in Au‐Ag bimetallic catalysts when applied to various oxidative reactions. One is based on the importance of the contact interfaces between AgOx regions and the surface of the bulk Au as active working sites, while the other holds that charge transfer from Ag to Au in a surface Au‐Ag alloy causes the catalytic activity. One key point in examining these theories and determining the origin of the synergy in‐volves determining whether or not Ag exists as an oxide or as a metallic alloy on the Au surface. To confirm that enhanced activity results from contact between Ag2O and Au nanoparticles （NPs）, a comparative study of catalytic CO oxidation over Au/Ag2O and Ag2O was performed in the present work, using a closed recirculation reaction system. A reaction mixture consisting of a stoichiometric composition of CO and O2 （CO/O2=2/1） was supplied to both catalysts and the resulting pressure decrease rates were tracked, from which the amounts of gas consumed as well as the quantity of CO2 produced were determined. The steady state reactions of both Au/Ag2O and Ag2O did not lead to any meaningful difference in the rate of pressure decrease during the oxidation. The pressure decrease over both catalysts was attributed to the reduction of surface lattice O on Ag2O by CO. The results obtained for Au/Ag2O are in good agreement with previous data resulting from the use of Ag‐contaminated Au powder （Ag/Au‐b） having an oxidized surfaces. This finding suggests that the perimeters between AgOx zones and the bulk Au surface may not function as active sites during CO oxidation. A review of previous results obtained with Ag/Au‐b specimens having so‐called steady state surfaces indicates that AgOx species in such materials are reduced to the 0 state to form a Ag‐Au alloy that provides the active sites.展开更多
In this study,a series of Co_3O_4/ mildly oxidized graphite oxide(mGO) nanocatalysts(Co_3O_4/ mGO-l,Co_3O_4/ mGO-2 and Co_3O_4/mGO-3) were synthesized through solvothermal method and used as a mediator for the heterog...In this study,a series of Co_3O_4/ mildly oxidized graphite oxide(mGO) nanocatalysts(Co_3O_4/ mGO-l,Co_3O_4/ mGO-2 and Co_3O_4/mGO-3) were synthesized through solvothermal method and used as a mediator for the heterogeneous peroxymonosulfate(PMS)activation.The performance of CO_3O_4 / mGO/PMS system was investigated using acid orange 7(AO7).Results showed that Co_3O_4/mGO-3 had the best degradation efficiency of AO7 and the removal rate was above 90%in about 6 min.The phenomenon indicated the catalytic activity of Co_3O_4/mGO composites was related to the oxidation degree of graphite oxide(GO).In addition,experiments showed the content of Co_3O_4 had an effect on the catalytic activity.The composites were characterized with X-ray powder diffraction(XRD),FTIR,Raman,X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM).According to the charactrization and synergistic catalytic mechanism,the generation of Co—OH complexes found to be the initial step to activate PMS in the heterogeneous system of Co_3O_4/mGO hybrid.展开更多
Precipitation is often used for the preparation of La(OH)_(3)with precipitants of liquid alkali and ammonia.To solve the problems of high cost and wastewater pollution caused by common precipitants,the active MgO synt...Precipitation is often used for the preparation of La(OH)_(3)with precipitants of liquid alkali and ammonia.To solve the problems of high cost and wastewater pollution caused by common precipitants,the active MgO synthesized by pyrolysis was used as the precipitant to prepare La(OH)_(3).The species distribution of LaCl_(3)and LaCl_(3)-MgCl_(2)mixed system solution was calculated,and the kinetic analysis of the precipi-tation process was carried out to confirm the key factors influencing the precipitation of La(OH)_(3).The results show that La(OH)_(3)with D_(50)of 5.57μm,a specific surface area of 25.70 m^(2)/g,a rod-like shape,and MgO content of 0.044 wt%,was successfully prepared by adding active MgO.The precipitation ratio of La reaches 99.92%.The La(OH)_(3)precipitation is controlled by the diffusion process.The activity of MgO has a significant influence on MgO content in the precipitate.The preparation of La(OH)_(3)by active MgO provides a potential way for an eco-friendly preparation method of rare earth.展开更多
An electrochemically reduced graphene oxide sample, ERGO_0.8v, was prepared by electrochemical reduction of graphene oxide （GO） at -0.8 V, which shows unique electrocatalytic activity toward tetracycline （TTC） det...An electrochemically reduced graphene oxide sample, ERGO_0.8v, was prepared by electrochemical reduction of graphene oxide （GO） at -0.8 V, which shows unique electrocatalytic activity toward tetracycline （TTC） detection compared to the ERGO-12v （GO applied to a negative potential of-1.2 V）, GO, chemically reduced GO （CRGO）-modified glassy carbon electrode （GC） and bare GC electrodes. The redox peaks of TTC on an ERGO-0.8v-modifled glass carbon electrode （GC/ERGO-0.8v） were within 0-0.5 V in a pH 3.0 buffer solution with the oxidation peak current correlating well with TTC concentration over a wide range from 0.1 to 160 mg/L Physical characterizations with Fourier transform infrared （FT-IR）, Raman, and X-ray photoelectron spectroscopies （XPS） demonstrated that the oxygen-containing functional groups on GO diminished after the electrochemical reduction at -0.8 V, yet still existed in large amounts, and the defect density changed as new sp2 domains were formed. These changes demonstrated that this adjustment in the number of oxygen-containing groups might be the main factor affecting the electrocatalytic behavior of ERGO. Additionally, the defect density and sp2 domains also exert a profound influence on this behavior. A possible mechanism for the TTC redox reaction at the GC/ERGO-0.8v electrode is also presented. This work suggests that the electrochemical reduction is an effective method to establish new catalytic activities of GO by setting appropriate parameters.展开更多
Rechargeable Na-O2 batteries have attracted significant attention as energy storage devices owing to their theoretically high energy storage capacity and the natural abundance of sodium. However, practical application...Rechargeable Na-O2 batteries have attracted significant attention as energy storage devices owing to their theoretically high energy storage capacity and the natural abundance of sodium. However, practical applications of this type of battery still suffer from low specific capability, poor cycle sta- bility, instable electrolytes, and unstable polymer binders. Herein, we report a facile method of synthesizing binder free and flexible cathodes with C0304 nanowire arrays vertically grown onto carbon textiles. When employed as a cathode for Na-O2 batteries, this cathode exhibits superior performance, including a reduction of charge overpotential, high specific capacity （4687 mAh/g）, and cycle stability up to 62 cycles. These enhanced performance can be attributed to the synergistic effect of the porosity and catalytic activity of the C0304 nanowire catalyst.展开更多
Pd/C catalysts were prepared by deposited Pd nanoparticles （NPs） on different carbon supports including activated carbon （AC）, graphite oxide （GO）, and reduced graphite oxide （rGO） using sol-immobilization met...Pd/C catalysts were prepared by deposited Pd nanoparticles （NPs） on different carbon supports including activated carbon （AC）, graphite oxide （GO）, and reduced graphite oxide （rGO） using sol-immobilization method. Through transmission electron microscopy, powder X-ray di raction, and X-ray photoelectron spectroscopy, the role of the carbon supports for the catalytic performances of Pd/C catalysts was examined in selective hydrogenation of acetylene. The results indicate that Pd/AC exhibited higher activity and selectivity than Pd/GO and Pd/rGO in the gas phase selective hydrogenation of acetylene. Thermal and chemical treatment of AC supports also have some effect on the catalytic performance of Pd/AC catalysts. The differences in the activity and selectivity of various Pd/C catalysts were partly attributed to the metal-support interaction.展开更多
The high-energy lithium/sulfur(Li/S) battery has become a very popular topic of research in recent years due to its high theoretical capacity of 1672 m Ah/g. However, the polysulfide shuttle effect remains of great co...The high-energy lithium/sulfur(Li/S) battery has become a very popular topic of research in recent years due to its high theoretical capacity of 1672 m Ah/g. However, the polysulfide shuttle effect remains of great concern with a great number of publications dedicated to its mitigation. In this contribution, a three-dimensional(3D) reduced graphene oxide/activated carbon(RGO/AC) film, synthesized by a simple hydrothermal method and convenient mechanical pressing, is sandwiched between the separator and the sulfur-based cathode, acting as a functional interlayer to capture and trap polysulfide species. Consequently, the Li/S cell with this interlayer shows an impressive initial discharge capacity of 1078 m Ah/g and a reversible capacity of 655 m Ah/g even after 100 cycles. The RGO/AC interlayer impedes the movement of polysulfide while providing unimpeded channels for lithium ion mass transfer. Therefore, the RGO/AC interlayer with a well-designed structure represents strong potential for high-performance Li/S batteries.展开更多
基金financial support by the Program for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi(OIT)Shanxi Province Hundred Talent Project
文摘In recent decade, Au nanoclusters of atomic precision （AunLm, where L= organic ligand： thiolate andphosphine） have been shown as a new promising nanogold catalyst. The well-defined AunLm catalystspossess unique electronic properties and frameworks, providing an excellent opportunity to correlate theintrinsic catalytic behavior with the cluster＇s framework as well as to study the catalytic mechanismsover gold nanoclusters. In this review, we only demonstrate the important roles of the gold nanoclustersin the oxygen activation （e.g., 302 to 102） and their selective oxidations in the presence of oxygen （e.g., COto C02, sulfides to sulfoxides, alcohol to aldehyde, styrene to styrene epoxide, amines to imines, andglucose to gluconic acid）. The size-specificity （Au25 （1.3 nm）, Au38 （].5 nm）, Au144 （1.9 nm）, etc.）, ligandengineering （e.g., aromatic vs aliphatic）, and doping effects （e.g., copper, silver, palladium, and platinum）are discussed in details. Finally, the proposed reactions＇ mechanism and the relationships of clusters＇structure and activity at the atomic level also are presented.
基金Project(50974140) supported by the National Natural Science Foundation of ChinaProject(20090162110054) supported by Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘The apparent sulfur oxidation activities of four pure thermophilic archaea, Acidianus brierleyi （JCM 8954）, Metallosphaera sedula （YN 23）, Acidianus manzaensis （YN 25） and Sulfolobus metallicus （YN 24） and their mixture in bioleaching chalcopyrite were compared, which were characterized indirectly by the evolution of the cells concentration, pH value and sulfate ions concentration in solution. The results show that the mixed culture contributed significantly to the raising of leaching rate, which suggests that the mixed culture had a higher sulfur oxidation activity than the pure culture. Meanwhile, the results also indicate that the changes of parameters characterizing the sulfur oxidation activity of thermophilic archaea are often influenced by many factors, so it is hard to reflect accurately the specific sulfur oxidation activities among the different sulfur-oxidizing microbes when bioleaching chalcopyrite at different conditions. Accordingly, an efficient method to characterize microbial sulfur oxidation activity appears to be desirable.
基金supported by the National Natural Science Foundation of China (21263015)the Education Department of Jiangxi Province (KJLD14005)the Natural Science Foundation of Jiangxi Province(20151BBE50006,20122BAB203009)~~
文摘Polycrystalline SnO2 fine powder consisting of nano-particles （SnO2-NP）, SnO2 nano-sheets （SnO2-NS）, and SnO2 containing both nano-rods and nano-particles （SnO2-NR＋NP） were prepared and used for CO oxidation. SnO2-NS possesses a mesoporous structure and has a higher surface area, larger pore volume, and more active species than SnO2-NP, and shows improved activity. In contrast, although SnO2-NR＋NP has only a slightly higher surface area and pore volume, and slightly more active surface oxygen species than SnO2-NP, it has more exposed active （110） facets, which is the reason for its improved oxidation activity. Water vapor has only a reversible and weak influence on SnO2-NS, therefore it is a potential catalyst for emission control processes.
基金supported by the National Natural Science Foundation of China (No. 21107101)the Fundamental Research Funds for the Central Universities of China (Ocean University of China)(No.201113005)
文摘The effects of chloride anion （Cl-） （up to 1.0 mol/L） on the decolorization of a model compound,azo dye Acid Orange 7 （AO7）,by sulfate radical （SO4-） based-peroxydisulfate （PS） or peroxymonosulfate （PMS） oxidation under various activated conditions （UV 254 nm /PS,Thermal （70°C/PS,UV 254 nm /PMS,Co 2＋ /PMS） were investigated.Methanol and NH4 ＋ were used as quenching reagents to determine the contributions of active chlorine species （dichloride radical （Cl2-.） and hypochlorous acid （HClO））.The results indicated that the effects of Cl- on the reaction mechanism were different under various activated conditions.For UV/PS and Thermal/PS,the inhibition tendency became more clear as the Cl- concentration increased,probably due to the reaction between Cl- and SO4-.and the generation of Cl2-.or HClO.For UV/PMS,Cl- did not exhibit inhibition when the concentration was below 0.1 mol/L.As Cl- concentration reached to 1.0 mol/L,the decolorization rate of AO7 was,however,accelerated,possibly because PMS directly reacts with Cl- to form HClO.For Co2＋ /PMS,Cl- exhibited a significant inhibiting effect even at low concentration （ 0.01 mol/L）.When Cl- concentration exceeded 0.1 mol/L,the activation of PMS by Co 2＋ was almost completely inhibited.Under this condition,HClO maybe played a major role in decolorization of AO7.The results implicated that chloride ion is an important factor in SO4-.-based degradation of organic contamination in chloride-containing water.
基金supported by the Natural Science Foundation of Hubei Province (No.2009CDA050)the New Century Excellent Talents in University (No. NCET-10-0137)the National Natural Science Foundation of China (No. 51072143)
文摘The microstructural evolution and oxidation resistance of multi-walled carbon nanotubes （MWCNTs） by di- rectly heating silicon powder and MWCNTs in a coke bed from 1000 to 1500 ~C are investigated with the aid of X-ray diffraction （XRD）, scanning electron microscopy （SEM）, high resolution transmission electron microscopy （HRTEM） and thermogravimetry-differential scanning calorimetry （TG-DSC）. The results showed that the morphology and microstructure of MWCNTs did not change much after being treated from 1000 ~C to 1200 ~C. An obvious SiC coating was formed on the surface of MWCNTs from 1300 to 1400 ~C. Up to 1500 ~C, nearly all the MWCNTs transformed into SiC nanowires. The oxidation resistance of the treated MWCNTs was improved compared with as-received ones. Non-isothermal kinetics showed that the oxidation activation energy of the treated MWCNTs reached 208 kJ/mol, much higher than 264 k J/tool of as-received ones.
基金supported by the National Natrual Science of China (NSFC, Nos. 51978341, 52070100 and 52011530433)the Natural Science Foundation of Jiangsu Province of China (No. BK20190087)Jiangsu Key Laboratory of New Power Batteries, and a project funded by the Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institutions。
文摘Hydroxyl radicals(·OH) generated on anode play a vital role in electrochemical oxidation(EO) of organic pollutants for water treatment. Inspired by the four-electron oxygen evolution reaction(OER), we supposed an anode-selection strategy to stabilize deeply oxidized states(*O and*OOH) which are beneficial to generating·OH. To verify the hypothesis, a candidate anode component(MIL-101(Cr), a well-known metal-organic framework with active variable-valence transition metal centers) was used to coat Ti/TiO_(2)plate to fabricate anodes. Compared to TiO_(2)(101) plane on undecorated anode surface, fast and complete removal of aniline and phenol, and improved energy utilization were achieved on MIL-101(Cr)-coatedTi/TiO_(2)anode. Mechanism investigation, including pollutant degradation pathways, showed the predominate contribution(69.60%–75.13%) of·OH in pollutant mineralization. Density functional theory(DFT)computations indicated Cr site in MIL-101(Cr) was more conducive to stabilizing*O and*OOH, leading to thermodynamical spontaneous generation of·OH. This work opens up an exciting avenue to explore·OH production, and supplies a useful guidance to the development of anode materials for EO process.
基金Project supported by the National key research and development program(2016YFC0204901)the National Natural Science Foundation of China(21576207)the introduction of talent and technology cooperation plan of Tianjin(14RCGFGX00849)
文摘MnO_x-CeO_2 catalysts were synthesized to investigate the active sites for NO oxidation by varying the calcination temperature. XRD and TEM results showed that cubic CeO_2 and amorphous MnO_x existed in MnO_x-CeO_2 catalysts. High temperature calcination caused the sintering of amorphous MnO_x and transforming to bulk crystalline Mn_2O_3, H_2-TPR and XPS results suggested the valence of Mn in MnO_x-CeO_2 was higher than pure MnO_x, and decreased with the increasing calcination temperature, The turnover frequency（TOF） was calculated based on the initial reducibility according to H_2-TPR quantitation and kinetic study. The TOF results indicated that the initial reducibility of amorphous MnO_x with high valence manganese ions was equivalent to the active sites for NO oxidation. It can be inferred that the amorphous MnO_x plays a key role in low-temperature NO oxidation.
基金Sponsored by National Natural Science Foundation of China(51204047)National Key Technology Research and Development Program in 12th Five-year Plan of China(2011BAE13B04)The Fundamental Research Funds for the Central Universities of China(N100307006)
文摘The oxidation kinetics and composition of oxide scales on low carbon steel （SPHC） were studied during i- sothermal oxidation. Thermogravimetric analyzer （TGA） was used to simulate isothermal oxidation process of SPHC for 240 min under air condition, and the temperature range was from 500 to 900 ℃. Scanning electron microscope （SEM） was used to observe cross-sectional scale morphology and analyze composition distribution of oxide scales. The morphology of oxide scale was classical three-layer structure. Fe2 03 developed as whiskers at the outermost lay- er, and interlayer was perforated-plate Fe3 04 while innermost layer was pyramidal FeO. From the oxidation curves, the oxidation mass gain per unit area with time was of parabolic relation and oxidation rate slowed down. On the ba- sis of experimental data, the isothermal oxidation kinetics model was derived and oxidation activation energy of SPHC steel was 127. 416 kJ/mol calculated from kinetics data.
文摘Bioleaching of sulfide minerals by bacteria, mainly Thiobacillus ferrooxidans(T.f.) and Thiobacillus thiooxidans, plays an important role in hydrometallurgy because of its economic and environmental attractions. The surveys of production process and the bacterial oxidation activity in the heap bioleaching were investigated. The results show that pH value is high, bacteria biomass and ferric concentration are low, generation time (above 7.13 h) is long in leachate, and less bacteria are adsorbed on the ores. The bacteria in the leachate exposing on the surface and connecting with mineral, have much faster oxidation rate of Fe(Ⅱ) and shorter generation time, compared with those which are in the reservoir for a long time. There is diversity for oxidation activity of Fe(Ⅱ), while there is no diversity for oxidation of sulfur. So it is advisable to add sulfuric acid to degrade pH value to 2.0, add nutrients and shorten recycling time of leachate, so as to enhance bacteria concentration of leachate and the leaching efficiency.
基金supported by the National Natural Science Foundation of China (No. 21177130)the National Key Technology R&D Program (No. 2011BAC06B09)the Chinese Academy of Sciences Visiting Professorships for Senior International Scientists (No. 2009G2-28)
文摘Ozonation of oxalate in aqueous phase was performed with a commercial activated carbon（AC）in this work. The effect of AC dosage and solution pH on the contribution of hydroxyl radicals（HOU） in bulk solution and oxidation on the AC surface to the removal of oxalate was studied. We found that the removal of oxalate was reduced by tert-butyl alcohol（tBA） with low dosages of AC,while it was hardly affected by tBA when the AC dosage was greater than 0.3 g/L. tBA also inhibited ozone decomposition when the AC dosage was no more than 0.05 g/L, but it did not work when the AC dosage was no less than 0.1 g/L. These observations indicate that HOUin bulk solution and oxidation on the AC surface both contribute to the removal of oxalate. HOU oxidation in bulk solution is significant when the dosage of AC is low, whereas surface oxidation is dominant when the dosage of AC is high. The oxalate removal decreased with increasing pH of the solution with an AC dosage of 0.5 g/L. The degradation of oxalate occurs mainly through surface oxidation in acid and neutral solution, but through HOUoxidation in basic bulk solution. A mechanism involving both HOUoxidation in bulk solution and surface oxidation was proposed for AC enhanced ozonation of oxalate.
基金Project supported by the National key research and development program(2016YFC0204901)the National Natural Science Foundation of China(21576207)+1 种基金the Introduction Of Talent and Technology Cooperation Plan Of Tianjin(14RCGFGX00849)GM Global Research&Development(GAC 1539)
文摘This study was focused on the influence of active oxygen on the performance of Pt/CeO2 catalysts for CO oxidation. A series of CeO2 supports with different contents of active oxygen were obtained by adding surfactant at different synthesis steps. 0.25 wt% Pt was loaded on these CeO2 supports by incipientwetness impregnation methods. The catalysts were characterized by N2 adsorption, X-ray diffraction（XRD）, high-resolution transmission electron microscopy（HRTEM）, H2 temperature-programmed reduction（H2-TPR）, dynamic oxygen storage capacity（DOSC） and in-situ DRIFTS technologies. For S-f supports, the surfactant was added into the solution before spray-drying in the synthesis process, which facilitates more active oxygen formation on the surface of CeO2. After loading Pt, the more active oxygen on CeO2 contributes to dispersing Pt species and enhancing the CO oxidation activity. As for the aged samples,Pt-R-h shows the highest activity above 190 ℃ because of the presence of more partly oxidized Pt^（δ＋） species. Thus the activity is also influenced by the states of Pt and the Pt^（δ＋） species may contribute to the high activity at elevated temperature.
基金Project supported by the Introduction of Talent and Technology Cooperation Plan of Tianjin
文摘Pd@Zr/Ce O2 core-shell catalyst prepared by hydrothermal method was applied in CO oxidation reaction, exhibiting high CO oxidation activity at low temperature.XRD（X-ray diffraction） analysis demonstrated that the remarkable enhancement of catalytic performance was found to depend on the presence of more oxygen vacancies in the core-shell structure, which contributed higher content of and ready release of active oxygen species at low temperature, confirmed by H2-TPR（temperature programed reduction） results.Interestingly, introducing a small amount of zirconium（0.5 wt.%） exhibited a significant improvement of catalytic activity because the introduction of Zr further improved the amount of crystal defects and promoted the migration of oxygen species.
基金This work was supported by the Ministry of Science and Higher Education of the Russian Federation(projects No.FSWW-2020-0022 and AAAA-A17-117041710086-6).
文摘The oxidation of lignite and bituminous coal samples modified by 5 wt%(in terms of dry salt)addition of copper salts Cu(NO_(3))_(2),CuSO_(4),and Cu(CH_(3)COO)_(2) was studied.The samples’reactivity was studied by thermogravimetry within a temperature range of 45–600℃ at a heating rate of 2.5℃/min in an oxidizing environment.The introduction of activating additives has resulted in a significant decrease in the temperature of intense oxidation onset(ΔT_(i)=20/94℃),in a reduction in the sample residence time in the volatile matter release region(Δt_(e)=2/22 min)and the total duration of the coal combustible mass oxidation(Δt_(f)=8/14 min).The Friedman method was used to calculate the activation energy values for the oxidation process of the modified samples.The maximum change in activation energy values was observed for the bituminous coal sample.The possible mechanism behind the action of the copper-salt additives,which activate the oxidation of lignite and bituminous coal,is discussed.According to the data of mass spectrometric analysis,the concentration of NOx in the reaction products decreases as the temperature of the activated oxidation process is shifted towards the low-temperature region.
基金supported by CREST project(Catalyst Design of Gold Clusters through Junction Effect with Metal oxides,Carbons,and Polymers)sponsored by Japan Science and Technology Agency(JST)~~
文摘There are two theories regarding the origin of the remarkable synergistic effect observed in Au‐Ag bimetallic catalysts when applied to various oxidative reactions. One is based on the importance of the contact interfaces between AgOx regions and the surface of the bulk Au as active working sites, while the other holds that charge transfer from Ag to Au in a surface Au‐Ag alloy causes the catalytic activity. One key point in examining these theories and determining the origin of the synergy in‐volves determining whether or not Ag exists as an oxide or as a metallic alloy on the Au surface. To confirm that enhanced activity results from contact between Ag2O and Au nanoparticles （NPs）, a comparative study of catalytic CO oxidation over Au/Ag2O and Ag2O was performed in the present work, using a closed recirculation reaction system. A reaction mixture consisting of a stoichiometric composition of CO and O2 （CO/O2=2/1） was supplied to both catalysts and the resulting pressure decrease rates were tracked, from which the amounts of gas consumed as well as the quantity of CO2 produced were determined. The steady state reactions of both Au/Ag2O and Ag2O did not lead to any meaningful difference in the rate of pressure decrease during the oxidation. The pressure decrease over both catalysts was attributed to the reduction of surface lattice O on Ag2O by CO. The results obtained for Au/Ag2O are in good agreement with previous data resulting from the use of Ag‐contaminated Au powder （Ag/Au‐b） having an oxidized surfaces. This finding suggests that the perimeters between AgOx zones and the bulk Au surface may not function as active sites during CO oxidation. A review of previous results obtained with Ag/Au‐b specimens having so‐called steady state surfaces indicates that AgOx species in such materials are reduced to the 0 state to form a Ag‐Au alloy that provides the active sites.
基金Innovation Program of Shanghai Municipal Education Commission,China(No.12ZZ069)Research Fund for the Doctoral Program of Higher Education,China(No.20130075110006)
文摘In this study,a series of Co_3O_4/ mildly oxidized graphite oxide(mGO) nanocatalysts(Co_3O_4/ mGO-l,Co_3O_4/ mGO-2 and Co_3O_4/mGO-3) were synthesized through solvothermal method and used as a mediator for the heterogeneous peroxymonosulfate(PMS)activation.The performance of CO_3O_4 / mGO/PMS system was investigated using acid orange 7(AO7).Results showed that Co_3O_4/mGO-3 had the best degradation efficiency of AO7 and the removal rate was above 90%in about 6 min.The phenomenon indicated the catalytic activity of Co_3O_4/mGO composites was related to the oxidation degree of graphite oxide(GO).In addition,experiments showed the content of Co_3O_4 had an effect on the catalytic activity.The composites were characterized with X-ray powder diffraction(XRD),FTIR,Raman,X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM).According to the charactrization and synergistic catalytic mechanism,the generation of Co—OH complexes found to be the initial step to activate PMS in the heterogeneous system of Co_3O_4/mGO hybrid.
基金the National Key Research and Development Program of China(2022YFB3504503)the National Natural Science Foundation of China(52274355)the Gansu Province Science and Technology Major Special Project,China(22ZD6GD061).
文摘Precipitation is often used for the preparation of La(OH)_(3)with precipitants of liquid alkali and ammonia.To solve the problems of high cost and wastewater pollution caused by common precipitants,the active MgO synthesized by pyrolysis was used as the precipitant to prepare La(OH)_(3).The species distribution of LaCl_(3)and LaCl_(3)-MgCl_(2)mixed system solution was calculated,and the kinetic analysis of the precipi-tation process was carried out to confirm the key factors influencing the precipitation of La(OH)_(3).The results show that La(OH)_(3)with D_(50)of 5.57μm,a specific surface area of 25.70 m^(2)/g,a rod-like shape,and MgO content of 0.044 wt%,was successfully prepared by adding active MgO.The precipitation ratio of La reaches 99.92%.The La(OH)_(3)precipitation is controlled by the diffusion process.The activity of MgO has a significant influence on MgO content in the precipitate.The preparation of La(OH)_(3)by active MgO provides a potential way for an eco-friendly preparation method of rare earth.
基金supported by the National Natural Science Foundation of China(21007033)the Fundamental Research Funds of Shandong University(2015JC017)~~
文摘An electrochemically reduced graphene oxide sample, ERGO_0.8v, was prepared by electrochemical reduction of graphene oxide （GO） at -0.8 V, which shows unique electrocatalytic activity toward tetracycline （TTC） detection compared to the ERGO-12v （GO applied to a negative potential of-1.2 V）, GO, chemically reduced GO （CRGO）-modified glassy carbon electrode （GC） and bare GC electrodes. The redox peaks of TTC on an ERGO-0.8v-modifled glass carbon electrode （GC/ERGO-0.8v） were within 0-0.5 V in a pH 3.0 buffer solution with the oxidation peak current correlating well with TTC concentration over a wide range from 0.1 to 160 mg/L Physical characterizations with Fourier transform infrared （FT-IR）, Raman, and X-ray photoelectron spectroscopies （XPS） demonstrated that the oxygen-containing functional groups on GO diminished after the electrochemical reduction at -0.8 V, yet still existed in large amounts, and the defect density changed as new sp2 domains were formed. These changes demonstrated that this adjustment in the number of oxygen-containing groups might be the main factor affecting the electrocatalytic behavior of ERGO. Additionally, the defect density and sp2 domains also exert a profound influence on this behavior. A possible mechanism for the TTC redox reaction at the GC/ERGO-0.8v electrode is also presented. This work suggests that the electrochemical reduction is an effective method to establish new catalytic activities of GO by setting appropriate parameters.
基金supported by the 100 Talents Programme of the Chinese Academy of Sciencesthe National Basic Research Program of China(973 Program,2014CB932300,2012CB215500)the National Natural Science Foundation of China(21422108,51472232,51301160)~~
文摘Rechargeable Na-O2 batteries have attracted significant attention as energy storage devices owing to their theoretically high energy storage capacity and the natural abundance of sodium. However, practical applications of this type of battery still suffer from low specific capability, poor cycle sta- bility, instable electrolytes, and unstable polymer binders. Herein, we report a facile method of synthesizing binder free and flexible cathodes with C0304 nanowire arrays vertically grown onto carbon textiles. When employed as a cathode for Na-O2 batteries, this cathode exhibits superior performance, including a reduction of charge overpotential, high specific capacity （4687 mAh/g）, and cycle stability up to 62 cycles. These enhanced performance can be attributed to the synergistic effect of the porosity and catalytic activity of the C0304 nanowire catalyst.
文摘Pd/C catalysts were prepared by deposited Pd nanoparticles （NPs） on different carbon supports including activated carbon （AC）, graphite oxide （GO）, and reduced graphite oxide （rGO） using sol-immobilization method. Through transmission electron microscopy, powder X-ray di raction, and X-ray photoelectron spectroscopy, the role of the carbon supports for the catalytic performances of Pd/C catalysts was examined in selective hydrogenation of acetylene. The results indicate that Pd/AC exhibited higher activity and selectivity than Pd/GO and Pd/rGO in the gas phase selective hydrogenation of acetylene. Thermal and chemical treatment of AC supports also have some effect on the catalytic performance of Pd/AC catalysts. The differences in the activity and selectivity of various Pd/C catalysts were partly attributed to the metal-support interaction.
基金financial support from the National Natural Science Foundation of China(grant no.21406052the Program for the Outstanding Young Talents of Hebei Province(grant no.BJ2014010)the Scientific Research Foundation for Selected Overseas Chinese Scholars,Ministry of Human Resources and Social Security of China(grant no.CG2015003002)
文摘The high-energy lithium/sulfur(Li/S) battery has become a very popular topic of research in recent years due to its high theoretical capacity of 1672 m Ah/g. However, the polysulfide shuttle effect remains of great concern with a great number of publications dedicated to its mitigation. In this contribution, a three-dimensional(3D) reduced graphene oxide/activated carbon(RGO/AC) film, synthesized by a simple hydrothermal method and convenient mechanical pressing, is sandwiched between the separator and the sulfur-based cathode, acting as a functional interlayer to capture and trap polysulfide species. Consequently, the Li/S cell with this interlayer shows an impressive initial discharge capacity of 1078 m Ah/g and a reversible capacity of 655 m Ah/g even after 100 cycles. The RGO/AC interlayer impedes the movement of polysulfide while providing unimpeded channels for lithium ion mass transfer. Therefore, the RGO/AC interlayer with a well-designed structure represents strong potential for high-performance Li/S batteries.
