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
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 relations between catalytic activities and compositions of the systems Mg_xZn_(1-x)Fe_2O_4, Co_xZn_(1-x)Fe_2O_4, Co_xMg_(1-x)Fe_2O_4, Cd_xZn_(1-x)Fe_2O_4 and Mg_xZn_(1-x)Fe_2O_4·0.17Fe_2O_3 have been studied ...The relations between catalytic activities and compositions of the systems Mg_xZn_(1-x)Fe_2O_4, Co_xZn_(1-x)Fe_2O_4, Co_xMg_(1-x)Fe_2O_4, Cd_xZn_(1-x)Fe_2O_4 and Mg_xZn_(1-x)Fe_2O_4·0.17Fe_2O_3 have been studied by flow differential reactor, XRD, and derivative IR techniques. It has been found that the appropriate normal-inverse spinel combination substantially increases the activity for the title raction. The structure of the active site and the role of the bivalent cation in the title catalyst have been inferred.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
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
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
The relationship between iron oxides and surface charge characteristics in variable charge soils ( latosol and red earth ) was studied in following three ways. ( 1 ) Remove free iron oxides ( Fed ) and amorphous iron ...The relationship between iron oxides and surface charge characteristics in variable charge soils ( latosol and red earth ) was studied in following three ways. ( 1 ) Remove free iron oxides ( Fed ) and amorphous iron oxides ( Feo ) from the soils with sodium dithionite and acid ammonium oxalate solution respectively. ( 2 ) Add 2% glucose ( on the basis of air-dry soil weight ) to soils and incubate under submerged condition to activate iron oxides, and then the mixtures are dehydrated and air-dried to age iron oxides. ( 3 ) Precipitate various crystalline forms of iron oxides onto kaolinite. The results showed that free iron oxides ( Fed ) were the chief carrier of variable positive charges. Of which crystalline iron oxides ( Fed-Feo ) presented mainly as discrete particles in the soils and could only play a role of the carrier of positive charges, and did little influence on negative charges. Whereas the amorphous iron oxides ( Feo ) , which presented mainly as a coating with a large specific surface area, not only had positive charges, but also blocked the negative charge sites in soils. Submerged incubation activated iron oxides in the soils, and increased the amount of amorphous iron oxides and the degree of activation of iron oxide, which resulted in the increase of positive and negative charges of soils. Dehydration and air-dry aged iron oxides in soils and decreased the amount of amorphous iron oxides and the degree of activation of iron oxide, and also led to the decrease of positive and negative charges. Both the submerged incubation and the dehydration and air-dry had no significant influence on net charges. Precipitation of iron oxides onto kaolinite markedly increased positive charges and decreased negative charges. Amorphous iron oxide having a larger surface area contributed more positive charge sites and blocked more negative charge sites in kaolinite than crystalline goethite.展开更多
For further understanding of self-heating of coal, we tested the reactions of seven different ranks of coal under inert atmosphere. In the test, 50-gram of coal sample ranged from 0.18 mm to 0.38 mm was put into a spe...For further understanding of self-heating of coal, we tested the reactions of seven different ranks of coal under inert atmosphere. In the test, 50-gram of coal sample ranged from 0.18 mm to 0.38 mm was put into a special designed copper reaction vessel and let pure nitrogen to flow into the coal sample from the bottom at a rate of 100 mL/min. The programmed temperature enclosure was run at a programmed rate of 0.8 ~C/min. The concentration of the carbon oxides and the coal temperature were tested. The results show that the coal reactions under inert atmosphere can generate CO and C02. The reactions under inert atmosphere are affected by coal ranks, initial pore structure of coal and sulfur content. For low ranks of coal, the productions of carbon oxides are piecewise. The coal temperature is lower than the surrounding temperature throughout the reactions under inert atmosphere, but it rises quickly and reaches a crossing point temperature in the later stage under dry-air atmosphere. Based on the analysis, it indicates the self-reaction of initial active groups exists in the self-heating of coal besides the reactions in the two parallel reactions model. Spontaneous combustion of coal is due to both the oxidation heat accumulation and the chain reaction. A new reaction model of self-heating of coal was orooosed.展开更多
For the first time,Au nanoparticles on graphene oxide（GO-AuNPs） were successfully fabricated without applying any additional reductants,just by the redox reaction between AuCl_4^（-1） and GO.Their structure was cha...For the first time,Au nanoparticles on graphene oxide（GO-AuNPs） were successfully fabricated without applying any additional reductants,just by the redox reaction between AuCl_4^（-1） and GO.Their structure was characterized by transmission electron microscopy and X-ray powder diffraction.The results show that flower-like AuNPs were successfully dispersed on GO surface.Importantly,they showed a high catalytic activity for the Suzuki-Miyaura coupling reaction in an aqueous medium.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
To confirm sub-regular solution model valid for predicting the activity of component in binary oxide systems, seven systems in the whole concentration and twelve systems presenting saturation concentration have been s...To confirm sub-regular solution model valid for predicting the activity of component in binary oxide systems, seven systems in the whole concentration and twelve systems presenting saturation concentration have been studied. The total average relative errors of component 1 and 2 are 3.2 % and 4.1% respectively by application of the sub-regular solution model into the systems within the whole concentration. However, the total average relative errors are 16 % and 1088 % in the systems presenting saturation concentration. The results show that sub-regular solu- tion model is not good for predicting the systems presenting saturation concentration, especially for the systems con- taining acidic or neutral oxide. The reason may be that the influence of the two types of oxide on the configuration is greater in binary oxide systems. These oxides can be present in the form of complex anion partly, Si-O, Al-O, Ti-O and so on, for example （SiO4）4-. That is contrary to sub-regular solution model which is supposed that the oxide systems consist of cation and O2-. But compared with regular solution model and quasi-regular solution model, sub- regular solution model is closer to the characteristics of actual solution and the calculated results are superior.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 recovery of metal oxides from stainless steel dust using C（graphite）, SiFe, and Al as reductants was investigated under various conditions. The apparent distribution ratio of Cr（L Cr ′^m/s ） in the recovered ...The recovery of metal oxides from stainless steel dust using C（graphite）, SiFe, and Al as reductants was investigated under various conditions. The apparent distribution ratio of Cr（L Cr ′^m/s ） in the recovered metal and residual slag phases was defined as the major performance metric. The results show that the recovery ratio of metals increases as the ratio of CaO ：SiO2 by mass in the residual slag increases to 1.17. The residual content of metals in the slag decreases as the Al2O3 content of the slag is increased from approximately 8wt% to 10wt%. The recovery ratio of Cr increases with increasing L Cr ′^ m/s , and a linear relationship between L Cr ′^m/s and the activity coefficient ratio of CrO in the slag and the recovered metal phase is observed. The combination of C and SiFe or Al as the reducing agents reveals that Si is the more effective coreductant.展开更多
Magnesium oxide（MgO） is one of the metal oxides having unique properties with numerous potential industrial applications.In this study,MgO and vanadium-doped MgO nanoparticles were synthesized by sol–gel method in ...Magnesium oxide（MgO） is one of the metal oxides having unique properties with numerous potential industrial applications.In this study,MgO and vanadium-doped MgO nanoparticles were synthesized by sol–gel method in 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF_4] and 1-octyl-3-methylimidazolium tetrafluoroborate [OMIM][BF_4] ionic liquids.Vanadium-doped MgO nanoparticles exhibited nanosphere and nanorod morphologies with 40–80 nm in particle size,primarily due to the influence of ionic liquids as demonstrated by high-resolution scanning electron microscopy and transmission electron microscopy.Characteristics of nanoparticles were also studied by thermal gravimetric analysis,X-ray diffraction and energy-dispersive X-ray spectroscopy.Photodegradation ability of synthesized nanoparticles was evaluated for methylene blue（MB） in specially designed UV reactor.Photodegradation is found to be dependent on doping,and particle characteristics change due to the influence of ionic liquid.The ionic liquid-assisted vanadium-doped MgO nanoparticles showed good reusability under UV irradiation and MB degradation ability under visible light.展开更多
Cupric oxide （CuO） and copper-cuprous oxide （Cu-Cu2O） nanoparticles were prepared by a simple hydrothermal method for the synthesis of diethyi carbonate （DEC） from ethanol. During these syntheses, varying NaOH a...Cupric oxide （CuO） and copper-cuprous oxide （Cu-Cu2O） nanoparticles were prepared by a simple hydrothermal method for the synthesis of diethyi carbonate （DEC） from ethanol. During these syntheses, varying NaOH and glucose concentrations were applied to explore and pinpoint the active species. It was found that PdCl2/CuO and PdCI2/Cu-Cu2O both catalysts exhibited good thermal stability and morphology. The results of catalytic tests showed that the catalysts prepared with 5 mol/L NaOH show superior catalytic performances because of their lower extent of agglomeration. It is noteworthy that the PdC12/Cu-Cu2O catalysts were the most active, especially the PdCl2/Cu-Cu2O catalyst prepared with 10 mmol glucose and having a higher Cu2O concentration. In Pd（ll）-Cu（II） （PdCl2/CuO） catalysts, there is an induction period, during which Pd（II） is reduced to Pd（0）, that must occur prior to electron transfer between Pd and Cu, and this can slow the catalytic reaction. To further pinpoint the active species, PdCl2/Cu-Cu2O catalysts with different Cu2O contents were prepared by controlling the dosages of glucose. The maximum DEC yield obtained with these catalysts was 151.9 mg.g-1.h-1, corresponding to an ethanol conversion of 7.2% and 97.9% DEC selectivity on an ethanol basis. Therefore, it was concluded that Cu＋ was the active species in this catalytic system, possibly because a higher proportion of Cu＋ reduces the Pd2＋ concentration and limits the CO oxidation side reaction, thus increasing DEC selectivity. In addition, Cu＋ promotes electron transfer between Pd and Cu without an induction period, which could also promote the catalytic activity.展开更多
The process of preparing anodic oxide film containing active sites and electroless nickel plating on highly active rare earth magnesium alloy was developed.The formation mechanism of electroless nickel plating on acti...The process of preparing anodic oxide film containing active sites and electroless nickel plating on highly active rare earth magnesium alloy was developed.The formation mechanism of electroless nickel plating on active anodic oxide film and the structure and properties of the composite coating were studied by several surface and electrochemical techniques.The results showed that Ag nanograins with an average size of 10 nm were embedded into the anodic oxide film with pores of 0.1−2μm.Ag nanoparticles provided a catalytic site for the deposition of Ni-B alloy,and the Ni crystal nucleus was first grown in horizontal mode and then in cylindrical mode.The corrosion potential of the composite coating increased by 1.37 V and the corrosion current reduced two orders of magnitude due to the subsequent deposition of Ni-P alloy.The high corrosion resistance was attributed to the misaligning of these micro defects in the three different layers and the amorphous structure of the Ni-P alloy in the outer layer.These findings provide a new idea for electroless nickel plating on anodic oxide film.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
The catalytic activity of Perovskite-type mixed oxides (LaCoO3, PrCoO3 and SmCoO3) for the reduction of cyclohexanone to cyclohexanol with 2-propanol (Meerwein-PonndorfVerley reduction) has been studied. The data have...The catalytic activity of Perovskite-type mixed oxides (LaCoO3, PrCoO3 and SmCoO3) for the reduction of cyclohexanone to cyclohexanol with 2-propanol (Meerwein-PonndorfVerley reduction) has been studied. The data have been correlated with the surface electron donor properties of these mixed oxides展开更多
Zinc oxide, which has photocatalytic activity, is used as white pigment for cosmetics. A certain degree of sebum on the skin is decomposed by ultraviolet radiation in sunlight. In this work, zinc oxide was shaken with...Zinc oxide, which has photocatalytic activity, is used as white pigment for cosmetics. A certain degree of sebum on the skin is decomposed by ultraviolet radiation in sunlight. In this work, zinc oxide was shaken with phosphoric acid to synthesize a white pigment for cosmetics. Zinc oxide was set with 0.1 mol/L of phosphoric acid at P/Zn = 1/1 and 1/2, and then shaking in hot water for 1 h. The chemical composition, powder properties, photocatalytic activity, color phase, and smoothness of the obtained powder were studied. The P/Zn ratio in preparation had an effect on the reaction between phosphoric acid and zinc oxide. The photocatalytic activity of zinc oxide was inhibited by phosphoric acid treatment. The obtained samples had enough high reflectance at the visible light region.展开更多
Novel liver-specific nitric oxide（NO） releasing drugs with bile acid as both the NO carrier and targeting ligand were designed and synthesized by direct nitration of the hydroxyl group in bile acids or the 3-Ohydrox...Novel liver-specific nitric oxide（NO） releasing drugs with bile acid as both the NO carrier and targeting ligand were designed and synthesized by direct nitration of the hydroxyl group in bile acids or the 3-Ohydroxyl alkyl derivatives,with the intact 24-COOH being preserved for hepatocyte specific recognition.Preliminary biological evaluation revealed that oral administrated targeted conjugates could protect mice against acute liver damage induced by acetaminophen or carbon tetrachloride.The nitrate level in the liver significantly increased after oral administration of 1e while nitrate level in the blood did not significantly change.Co-administration of ursodeoxycholic acid（UDCA） significantly antagonized the increase of nitrate in the liver resulted by administration of 1e.展开更多
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Project supported by National Natural Science Foundation of P. R. China.
文摘The relations between catalytic activities and compositions of the systems Mg_xZn_(1-x)Fe_2O_4, Co_xZn_(1-x)Fe_2O_4, Co_xMg_(1-x)Fe_2O_4, Cd_xZn_(1-x)Fe_2O_4 and Mg_xZn_(1-x)Fe_2O_4·0.17Fe_2O_3 have been studied by flow differential reactor, XRD, and derivative IR techniques. It has been found that the appropriate normal-inverse spinel combination substantially increases the activity for the title raction. The structure of the active site and the role of the bivalent cation in the title catalyst have been inferred.
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.
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The relationship between iron oxides and surface charge characteristics in variable charge soils ( latosol and red earth ) was studied in following three ways. ( 1 ) Remove free iron oxides ( Fed ) and amorphous iron oxides ( Feo ) from the soils with sodium dithionite and acid ammonium oxalate solution respectively. ( 2 ) Add 2% glucose ( on the basis of air-dry soil weight ) to soils and incubate under submerged condition to activate iron oxides, and then the mixtures are dehydrated and air-dried to age iron oxides. ( 3 ) Precipitate various crystalline forms of iron oxides onto kaolinite. The results showed that free iron oxides ( Fed ) were the chief carrier of variable positive charges. Of which crystalline iron oxides ( Fed-Feo ) presented mainly as discrete particles in the soils and could only play a role of the carrier of positive charges, and did little influence on negative charges. Whereas the amorphous iron oxides ( Feo ) , which presented mainly as a coating with a large specific surface area, not only had positive charges, but also blocked the negative charge sites in soils. Submerged incubation activated iron oxides in the soils, and increased the amount of amorphous iron oxides and the degree of activation of iron oxide, which resulted in the increase of positive and negative charges of soils. Dehydration and air-dry aged iron oxides in soils and decreased the amount of amorphous iron oxides and the degree of activation of iron oxide, and also led to the decrease of positive and negative charges. Both the submerged incubation and the dehydration and air-dry had no significant influence on net charges. Precipitation of iron oxides onto kaolinite markedly increased positive charges and decreased negative charges. Amorphous iron oxide having a larger surface area contributed more positive charge sites and blocked more negative charge sites in kaolinite than crystalline goethite.
基金Financial supports for this research provided by the National Natural Science Foundation of China (No. 50927403)the Fundamental Research Funds for the Central Universities (No.2011RC06)the Jiangsu Natural Science Foundation (No.BK2009004)
文摘For further understanding of self-heating of coal, we tested the reactions of seven different ranks of coal under inert atmosphere. In the test, 50-gram of coal sample ranged from 0.18 mm to 0.38 mm was put into a special designed copper reaction vessel and let pure nitrogen to flow into the coal sample from the bottom at a rate of 100 mL/min. The programmed temperature enclosure was run at a programmed rate of 0.8 ~C/min. The concentration of the carbon oxides and the coal temperature were tested. The results show that the coal reactions under inert atmosphere can generate CO and C02. The reactions under inert atmosphere are affected by coal ranks, initial pore structure of coal and sulfur content. For low ranks of coal, the productions of carbon oxides are piecewise. The coal temperature is lower than the surrounding temperature throughout the reactions under inert atmosphere, but it rises quickly and reaches a crossing point temperature in the later stage under dry-air atmosphere. Based on the analysis, it indicates the self-reaction of initial active groups exists in the self-heating of coal besides the reactions in the two parallel reactions model. Spontaneous combustion of coal is due to both the oxidation heat accumulation and the chain reaction. A new reaction model of self-heating of coal was orooosed.
基金supported by the National Science Foundation of China(No.21074089)Tianjin Municipal Science and Technology Commission,China(No.09JCZDJC23300)
文摘For the first time,Au nanoparticles on graphene oxide（GO-AuNPs） were successfully fabricated without applying any additional reductants,just by the redox reaction between AuCl_4^（-1） and GO.Their structure was characterized by transmission electron microscopy and X-ray powder diffraction.The results show that flower-like AuNPs were successfully dispersed on GO surface.Importantly,they showed a high catalytic activity for the Suzuki-Miyaura coupling reaction in an aqueous medium.
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Item Sponsored by National Natural Science Foundation of China(50764006,50574045)Yunnan Basic Applied Research Foundation of China(2006E0021M)
文摘To confirm sub-regular solution model valid for predicting the activity of component in binary oxide systems, seven systems in the whole concentration and twelve systems presenting saturation concentration have been studied. The total average relative errors of component 1 and 2 are 3.2 % and 4.1% respectively by application of the sub-regular solution model into the systems within the whole concentration. However, the total average relative errors are 16 % and 1088 % in the systems presenting saturation concentration. The results show that sub-regular solu- tion model is not good for predicting the systems presenting saturation concentration, especially for the systems con- taining acidic or neutral oxide. The reason may be that the influence of the two types of oxide on the configuration is greater in binary oxide systems. These oxides can be present in the form of complex anion partly, Si-O, Al-O, Ti-O and so on, for example （SiO4）4-. That is contrary to sub-regular solution model which is supposed that the oxide systems consist of cation and O2-. But compared with regular solution model and quasi-regular solution model, sub- regular solution model is closer to the characteristics of actual solution and the calculated results are superior.
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financially supported by the National Natural Science Foundation of China (No. 51474021)the Fundamental Research Funds for the Central Universities of China (No. FRF-SD-12-009A)
文摘The recovery of metal oxides from stainless steel dust using C（graphite）, SiFe, and Al as reductants was investigated under various conditions. The apparent distribution ratio of Cr（L Cr ′^m/s ） in the recovered metal and residual slag phases was defined as the major performance metric. The results show that the recovery ratio of metals increases as the ratio of CaO ：SiO2 by mass in the residual slag increases to 1.17. The residual content of metals in the slag decreases as the Al2O3 content of the slag is increased from approximately 8wt% to 10wt%. The recovery ratio of Cr increases with increasing L Cr ′^ m/s , and a linear relationship between L Cr ′^m/s and the activity coefficient ratio of CrO in the slag and the recovered metal phase is observed. The combination of C and SiFe or Al as the reducing agents reveals that Si is the more effective coreductant.
文摘Magnesium oxide（MgO） is one of the metal oxides having unique properties with numerous potential industrial applications.In this study,MgO and vanadium-doped MgO nanoparticles were synthesized by sol–gel method in 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF_4] and 1-octyl-3-methylimidazolium tetrafluoroborate [OMIM][BF_4] ionic liquids.Vanadium-doped MgO nanoparticles exhibited nanosphere and nanorod morphologies with 40–80 nm in particle size,primarily due to the influence of ionic liquids as demonstrated by high-resolution scanning electron microscopy and transmission electron microscopy.Characteristics of nanoparticles were also studied by thermal gravimetric analysis,X-ray diffraction and energy-dispersive X-ray spectroscopy.Photodegradation ability of synthesized nanoparticles was evaluated for methylene blue（MB） in specially designed UV reactor.Photodegradation is found to be dependent on doping,and particle characteristics change due to the influence of ionic liquid.The ionic liquid-assisted vanadium-doped MgO nanoparticles showed good reusability under UV irradiation and MB degradation ability under visible light.
基金supported by the National Natural Science Foundation of China(21106054)~~
文摘Cupric oxide （CuO） and copper-cuprous oxide （Cu-Cu2O） nanoparticles were prepared by a simple hydrothermal method for the synthesis of diethyi carbonate （DEC） from ethanol. During these syntheses, varying NaOH and glucose concentrations were applied to explore and pinpoint the active species. It was found that PdCl2/CuO and PdCI2/Cu-Cu2O both catalysts exhibited good thermal stability and morphology. The results of catalytic tests showed that the catalysts prepared with 5 mol/L NaOH show superior catalytic performances because of their lower extent of agglomeration. It is noteworthy that the PdC12/Cu-Cu2O catalysts were the most active, especially the PdCl2/Cu-Cu2O catalyst prepared with 10 mmol glucose and having a higher Cu2O concentration. In Pd（ll）-Cu（II） （PdCl2/CuO） catalysts, there is an induction period, during which Pd（II） is reduced to Pd（0）, that must occur prior to electron transfer between Pd and Cu, and this can slow the catalytic reaction. To further pinpoint the active species, PdCl2/Cu-Cu2O catalysts with different Cu2O contents were prepared by controlling the dosages of glucose. The maximum DEC yield obtained with these catalysts was 151.9 mg.g-1.h-1, corresponding to an ethanol conversion of 7.2% and 97.9% DEC selectivity on an ethanol basis. Therefore, it was concluded that Cu＋ was the active species in this catalytic system, possibly because a higher proportion of Cu＋ reduces the Pd2＋ concentration and limits the CO oxidation side reaction, thus increasing DEC selectivity. In addition, Cu＋ promotes electron transfer between Pd and Cu without an induction period, which could also promote the catalytic activity.
基金Project(5227010679)supported by the National Natural Science Foundation of China。
文摘The process of preparing anodic oxide film containing active sites and electroless nickel plating on highly active rare earth magnesium alloy was developed.The formation mechanism of electroless nickel plating on active anodic oxide film and the structure and properties of the composite coating were studied by several surface and electrochemical techniques.The results showed that Ag nanograins with an average size of 10 nm were embedded into the anodic oxide film with pores of 0.1−2μm.Ag nanoparticles provided a catalytic site for the deposition of Ni-B alloy,and the Ni crystal nucleus was first grown in horizontal mode and then in cylindrical mode.The corrosion potential of the composite coating increased by 1.37 V and the corrosion current reduced two orders of magnitude due to the subsequent deposition of Ni-P alloy.The high corrosion resistance was attributed to the misaligning of these micro defects in the three different layers and the amorphous structure of the Ni-P alloy in the outer layer.These findings provide a new idea for electroless nickel plating on anodic oxide film.
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.
文摘The catalytic activity of Perovskite-type mixed oxides (LaCoO3, PrCoO3 and SmCoO3) for the reduction of cyclohexanone to cyclohexanol with 2-propanol (Meerwein-PonndorfVerley reduction) has been studied. The data have been correlated with the surface electron donor properties of these mixed oxides
文摘Zinc oxide, which has photocatalytic activity, is used as white pigment for cosmetics. A certain degree of sebum on the skin is decomposed by ultraviolet radiation in sunlight. In this work, zinc oxide was shaken with phosphoric acid to synthesize a white pigment for cosmetics. Zinc oxide was set with 0.1 mol/L of phosphoric acid at P/Zn = 1/1 and 1/2, and then shaking in hot water for 1 h. The chemical composition, powder properties, photocatalytic activity, color phase, and smoothness of the obtained powder were studied. The P/Zn ratio in preparation had an effect on the reaction between phosphoric acid and zinc oxide. The photocatalytic activity of zinc oxide was inhibited by phosphoric acid treatment. The obtained samples had enough high reflectance at the visible light region.
基金supported by the National High Technology Research and Development (863) Project (No. 2006AA02A4C6)National Natural Science Foundation of China (Nos. 30572220 and 30972626)
文摘Novel liver-specific nitric oxide（NO） releasing drugs with bile acid as both the NO carrier and targeting ligand were designed and synthesized by direct nitration of the hydroxyl group in bile acids or the 3-Ohydroxyl alkyl derivatives,with the intact 24-COOH being preserved for hepatocyte specific recognition.Preliminary biological evaluation revealed that oral administrated targeted conjugates could protect mice against acute liver damage induced by acetaminophen or carbon tetrachloride.The nitrate level in the liver significantly increased after oral administration of 1e while nitrate level in the blood did not significantly change.Co-administration of ursodeoxycholic acid（UDCA） significantly antagonized the increase of nitrate in the liver resulted by administration of 1e.
