In order to effectively separate galena and jamesonite and improve the recovery during the mixing flotation, the interaction mechanisms between the minerals and the collector of diethyl dithiocarbamate （DDTC） were i...In order to effectively separate galena and jamesonite and improve the recovery during the mixing flotation, the interaction mechanisms between the minerals and the collector of diethyl dithiocarbamate （DDTC） were investigated. Single mineral flotation test was organized to research the effect of pulp pH value on the flotation behavior of galena and jamesonite. Electrochemistry property of the interaction of these two minerals with DDTC was investigated by cyclic voltammetry and Tafel tests. Flotation test shows that the recovery of jamesonite in high alkaline pulp is strongly depressed by lime （Ca（OH）2）. The cyclic voltammetry and Tafel tests results show that the interaction between galena and DDTC is an electrochemical process. High pH value has little influence on the interaction between galena and DDTC, while it has great effect on jamesonite due to self-oxidation and specific adsorption of OH^- and CaOH^＋ on jamesonite surface. Non-electroactive hydroxyl compound and low-electroconductive calcium compounds cover the surface of jamesonite, which impedes electron transfer and DDTC adsorption, thus leads to very low floatability of jamesonite.展开更多
Electrochemical behavior of layered LiNi0.5Mn0.5O2 in LiNO3 aqueous solution and its cyclic fading mechanism in electrolytes with different pH values were investigated. CV results show that LiNi0.5Mn0.5O2 has good ele...Electrochemical behavior of layered LiNi0.5Mn0.5O2 in LiNO3 aqueous solution and its cyclic fading mechanism in electrolytes with different pH values were investigated. CV results show that LiNi0.5Mn0.5O2 has good electrochemical reversible behaviors in 5 mol/L LiNO3 solution. Meanwhile, the electrode in 5 mol/L LiNO3 with pH value of 12 demonstrates the best electrochemical stability. Based on the electrochemical impedance spectroscopy （EIS）, X-ray diffraction （XRD） and scanning electron microscopy （SEM） results, it is proposed that suppressed charge-transfer resistance is the major reason, which is probably ascribed to the more stable electrode surface and less structure change.展开更多
Growth and crystallization of titanium anodized films were studied by performing the anodization of the sputter-deposited titanium samples under cyclic voltammetry （CV） mode at very low potentials. The surface featu...Growth and crystallization of titanium anodized films were studied by performing the anodization of the sputter-deposited titanium samples under cyclic voltammetry （CV） mode at very low potentials. The surface features, crystalline behaviors and chemical compositions of the formed anodic oxide layers were detected by AFM, SE and XPS. It was found that the structure of the titanium anodized films is crystalline, even though the maximum oxidation potential （（Pmax） is very low （as low as 1000 mY）. Both enlarging the applied voltage and reducing the potential scanning rate are beneficial for the growth and crystallization of titanium oxide films. It was thought that the internal compressive stress, other than the local joule heating accepted for many researchers, is the main force of stimulating the crystallization of anodic titanium oxide films at very low potentials.展开更多
Aim To investigate the electrochemical behaviors of Mitomycin C （MC） and its interaction with calf thymus DNA （ctDNA）. Methods The cyclic vohammetry （CV） was carried out at a paraffined graphite electrode. Resul...Aim To investigate the electrochemical behaviors of Mitomycin C （MC） and its interaction with calf thymus DNA （ctDNA）. Methods The cyclic vohammetry （CV） was carried out at a paraffined graphite electrode. Results MC showed a well-defined oxidation-reduction peak. As a result of reaction with ctDNA, the peak current of MC decreased apparently. According to corresponding electrochemical equations, the diffusion coefficient of both free and MC-DNA complex have been determined, and the heterogeneous rate constants were also obtained simultaneously. Conclusion The solid paraffined graphite electrode could be used to estimate parameters of the interaction between DNA and MC, and provide the convenient and sensitive analysis.展开更多
The electrodeposition of lead in alkaline solutions containing xylitol （1, 2, 3, 4, 5-pentahydroxypentane） was studied. The lead electrodeposition and the chemical stability of xylitol in alkaline solutions were inv...The electrodeposition of lead in alkaline solutions containing xylitol （1, 2, 3, 4, 5-pentahydroxypentane） was studied. The lead electrodeposition and the chemical stability of xylitol in alkaline solutions were investigated by cyclic voltammetry. Apparent activation energy, apparent transfer coefficient and exchange current density were obtained by linear sweep voltammetry. Initial stages of lead electrocrystallization were determined by chronoamperometry. Voltammograms of a AISI 316 stainless steel electrode in xylitol solution exhibit no current in the potential range of-1.3 V to 0.75 V （vs Hg/HgO）, implying that xylitol is stable to oxidation and reduction. The apparent activation energy, apparent transfer coefficient and exchange current density were calculated to be 35.15 kJ/mol, 1.56 and 9.65x10^-5 A/m^2. Analysis of the chronoamperometric responses implies three-dimensional growth of nuclei, with the type of nucleation depending on overpotential.展开更多
Effects of meta-substituent of 3,4＇/4,3＇/3,3＇-substituted benzylideneanilines （XBAYs） on the electrochemical reduction potentials （E（Red）） were investigated, in which 49 samples of target compounds were synth...Effects of meta-substituent of 3,4＇/4,3＇/3,3＇-substituted benzylideneanilines （XBAYs） on the electrochemical reduction potentials （E（Red）） were investigated, in which 49 samples of target compounds were synthesized, and their reduction potentials were measured by cyclic voltammetry. The substituent effects on the E（Red） of target compounds were analyzed and an optimality equation with four parameters （Hammett constant a of X, Hammett constant a of Y, excited-state substituent constant σexCC of X, and the substituent specific cross-interaction effect △σexCC2 between X and Y） was obtained. The results show that the factors affecting the E（Red） of 3,4＇/4,31/3,3P-substituted XBAYs are different from those of 4,4＇-substituted XBAYs. For 3,4＇/4,3＇/3,3＇-substituted XBAYs, σ（X） and σ（Y） must be employed, and the contribution of △σexCC2 is important and not negligible. Compared with 4,4＇-substituted XBAYs, X group contributes less to 3,4＇/4,3＇/3,3＇-substituted XBAYs, while Y group contributes more to them. Additionally, it was observed that either para-substituted XBAYs or meta-substituted XBAYs, the substituent effects of X are larger than those of Y on the E（Red） of substituted XBAYs.展开更多
To investigate the electrochemical reduction mechanism of Ta(Ⅴ)in ethylene carbonate and aluminum chloride(EC-AlCl3)solvate ionic liquid,cyclic voltammetry experiments were conducted on a tungsten working electrode.F...To investigate the electrochemical reduction mechanism of Ta(Ⅴ)in ethylene carbonate and aluminum chloride(EC-AlCl3)solvate ionic liquid,cyclic voltammetry experiments were conducted on a tungsten working electrode.Four reduction peaks were observed in the cyclic voltammogram of the EC-AlCl3-TaCl5 ionic liquid.The reduction peaks at-0.55,-0.72,and-1.12 V(vs Al)were related to the reduction of Ta(Ⅴ)to tantalum metal by three stages including the formation of Ta(Ⅳ)and Ta(Ⅲ)complex ions.The reduction of Ta(Ⅲ)to tantalum metal was an irreversible diffusion-controlled reaction with a diffusion coefficient of 3.7×10^-7 cm^2/s at 323 K,and the diffusion activation energy was 77 k J/mol.Moreover,the cathode products at 323 K were characterized by scanning electron microscopy,energy-dispersive spectroscopy,and X-ray photoelectron spectroscopy.The results showed that tantalum metal and tantalum oxides were obtained by potentiostatic electrodeposition at-0.8 V for 2 h.展开更多
The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 t...The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 to 910 mA·h/g at 500 mA/g during 550 consecutive discharge/charge cycles,and delivers an ultrahigh capacity of 1276 mA·h/g at 100 mA/g,which is much greater than the theoretical capacity of either ZnMn2O4 or Mn3O4 electrode.To investigate the underlying mechanism of this phenomenon,cyclic voltammetry and differential capacity analysis were applied,both of which reveal the emergence and the growth of new reversible redox reactions upon charge/discharge cycling.The new reversible conversions are probably the results of an activation process of the electrode material during the cycling process,leading to the climbing charge storage.However,the capacity exceeding the theoretical value indicates that there are still other factors contributing to the increasing capacity.展开更多
The density,conductivity,and viscosity of the 1,3-dimethyl-2-imidazolinone and lithium nitrate(DMILiNO_(3))solvated ionic liquid were measured as a function of temperature.Additionally,the electrochemical mechanism an...The density,conductivity,and viscosity of the 1,3-dimethyl-2-imidazolinone and lithium nitrate(DMILiNO_(3))solvated ionic liquid were measured as a function of temperature.Additionally,the electrochemical mechanism and electrodeposition of neodymium from the DMI-LiNO_(3) solvated ionic liquid were investigated.Cyclic voltammetry results indicate that the electrochemical reduction of Nd(Ⅲ)is irreversible and proceeds via one-step with three-electron transfer,which is controlled by diffusion with a diffusion coefficient of 5.08×10^(-8) cm^(2)/s.Energydispersive X-ray spectrometry and X-ray photoelectron spectroscopy data confirm that the electrodeposit obtained after electrodeposition at-4 V(vs Ag)using the DMI-LiNO_(3)-Nd(CF_(3)SO_(3))_(3) solvated ionic liquid contains metallic neodymium.展开更多
In this article, the electrochemical performance of the electrodes of zinc polycrystal, Zn（002） and Zn（100） single crystals were studied by the Tafel line extrapolation of the potentio-dynamic polarization curves,...In this article, the electrochemical performance of the electrodes of zinc polycrystal, Zn（002） and Zn（100） single crystals were studied by the Tafel line extrapolation of the potentio-dynamic polarization curves, the cyclic voltammetry and the charge/discharge experiment. The results shows that in 6.0 mol·L^-1 KOH solution the corrosion rate of Zn polycrystal, Zn（100） and Zn（002） single crystals decreases in turn; and the reversibility and the charge/discharge performance of Zn single crystal was superior to Zn polycrystal. The dendrite growth of the surface of Zn polycrvstal was easier than Zn single crystal during the stages of charge/discharge.展开更多
Zinc chloride(ZnCl_(2))was dissolved in the 1,3-dimethyl-2-imidazolinone(DMI)solvent,and the metallic zinc coatings were obtained by electrodeposition in room-temperature ambient air.The conductivity(σ),viscosity(η)...Zinc chloride(ZnCl_(2))was dissolved in the 1,3-dimethyl-2-imidazolinone(DMI)solvent,and the metallic zinc coatings were obtained by electrodeposition in room-temperature ambient air.The conductivity(σ),viscosity(η),and density(ρ)of the DMI−ZnCl_(2)solvated ionic liquid at various temperatures(T)were measured and fitted.Furthermore,cyclic voltammetry was used to study the electrochemical behavior of Zn(II)in the DMI−ZnCl_(2)solvated ionic liquid,indicating that the reduction of Zn(II)on the tungsten electrode was a one-step two-electron transfer irreversible process.XRD and SEM−EDS analysis of the cathode product confirmed that the deposited coating was metallic zinc.Finally,the effects of deposition potential,temperature and duration on the morphology of zinc coatings were investigated.The results showed that a dense and uniform zinc coating was obtained by potentiostatic electrodeposition at−2 V(vs Pt)and 353 K for 1 h.展开更多
Alloy anodes were studied for pursuing Sn-based microcomposite synthesis, assembly and performance for lithium ion batteries. The self-assembled Sn-Co-C composites with nano-scaled microstructures were prepared via so...Alloy anodes were studied for pursuing Sn-based microcomposite synthesis, assembly and performance for lithium ion batteries. The self-assembled Sn-Co-C composites with nano-scaled microstructures were prepared via solution method and carbothermal technology. The morphology and physical structure were investigated with scanning electron microscope (SEM) and X-ray diffraction (XRD). The as-prepared materials were assembled to half cell coin for the purpose of discussing the galvanostatic cycling, cyclic voltammetry and rate-capability performance. Results reveal that nanoscaled CoSn 2 alloys covered with Sn and C layer by layer are wrapped by cross-linked porous carbon network to form spherical microstructure. This distinguishing feature of Sn-Co-C composites provides a possible solution to the problems of Sn particle aggregation and poor electron transport, and has strong effect on improving electrochemical performance.展开更多
The effect of two alkylpyridinium ionic liquids （py-iLs） including N-butylpyridinium hydrogen sulfate （BpyHSO4） and N-hexylpyridinium hydrogen sulfate （HpyHSO4） on the kinetics of copper electrodeposition from a...The effect of two alkylpyridinium ionic liquids （py-iLs） including N-butylpyridinium hydrogen sulfate （BpyHSO4） and N-hexylpyridinium hydrogen sulfate （HpyHSO4） on the kinetics of copper electrodeposition from acidic sulfate solution was investigated by cyclic voltammetry and potentiodynamic polarization measurements. Results from cyclic voltammetry indicate that these py-iLs have a pronounced inhibiting effect on CuE＋ electroreduction and there exists a typical nucleation and growth process. Kinetic parameters such as Tafel slope, transfer coefficient and exchange current density obtained from Tafel plots, lead to the conclusion that py-iLs inhibit the charge transfer by slightly changing the copper electrodeposition mechanism through their adsorption on the cathodic surface. In addition, scanning electron microscope （SEM） and X-ray diffraction analyses reveal that the presence of these additives leads to more leveled and fine-grained cathodic deposits without changing the crystal structure of the electrodeposited copper but strongly affects the crystallographic orientation by significantly inhibiting the growth of （111）, （200） and （311） planes.展开更多
The novel covalently modified glassy carbon electrode with poly(xylitol) was prepared using an electropolymerization technique for the simultaneous determination of uric acid(UA), xanthine(XA) and hypoxanthine(HX). Th...The novel covalently modified glassy carbon electrode with poly(xylitol) was prepared using an electropolymerization technique for the simultaneous determination of uric acid(UA), xanthine(XA) and hypoxanthine(HX). This new electrode presents an excellent electrocatalytic activity towards the oxidation of UA, XA and HX by cyclic voltammetry(CV) method. The oxidation peaks of the three compounds were well defined and had enhanced the peak currents. The separation potentials of the oxidation peak potentials for UA-XA and XA-HX were 380 and 370 mV in CV, respectively. Using differential pulse voltammetry(DPV) method, the calibration curves in the ranges of 5-55, 1.3-75.3 and 4-59 μmol/L were obtained for HX, XA and UA, respectively. The lowest detection limits(S/N=3) were 4.5, 0.75 and 3.75 μmol/L for HX, XA and UA, respectively. The practical application of the modified electrode was demonstrated by the determination of UA, XA, HX in human urine samples.展开更多
A reduced graphene oxide/Ni(OH)2 composite with excellent supercapacitive performance was synthesized by a facile hydrothermal route without organic solvents or templates used.XRD and SEM results reveal that the nicke...A reduced graphene oxide/Ni(OH)2 composite with excellent supercapacitive performance was synthesized by a facile hydrothermal route without organic solvents or templates used.XRD and SEM results reveal that the nickel hydroxide,which crystallizes into hexagonal β-Ni(OH)2 nanoflakes with a diameter less than 200 nm and a thickness of about 10 nm,is well combined with the reduced graphene oxide sheets.Electrochemical performance of the synthesized composite as an electrode material was investigated by cyclic voltammetry,electrochemical impedance spectroscopy and galvanostatic charge/discharge measurements.Its specific capacitance is determined to be 1672 F/g at a scan rate of 2 mV/s,and 696 F/g at a high scan rate of 50 mV/s.After 2000 cycles at a current density of 10 A/g,the composite exhibits a specific capacitance of 969 F/g,retaining about 86% of its initial capacitance.The composite delivers a high energy density of 83.6 W·h/kg at a power density of 1.0 kW/kg.The excellent supercapacitive performance along with the easy synthesis method allows the synthesized composite to be promising for supercapacitor applications.展开更多
Carboxyl graphene modified CuxO/Cu electrode was fabricated. The bare copper electrode was firstly anodic polarized in 1.0 mol/L NaOH solution in order to get CuxO nanoparticles, then the carboxyl graphene （CG） was ...Carboxyl graphene modified CuxO/Cu electrode was fabricated. The bare copper electrode was firstly anodic polarized in 1.0 mol/L NaOH solution in order to get CuxO nanoparticles, then the carboxyl graphene （CG） was electrodeposited on the CuxO/Cu electrode by cyclic potential sweeping. The electrocatalytic oxidation behaviors of calcium folinate （CF） at the graphene modified CuxO/Cu electrode were investigated by cyclic voltammetry. A positive scan polarization reverse catalytic voltammetry was used to obtain the pure catalytic oxidation current. The graphene modified CuxO/Cu electrode was served as the electrochemical sensor of CF, a highly sensitivity of 22.0μA.（μmol/μL）^-1cm^-2 was achieved, and the current response was linear with increasing CF concentration in the range of 2.0×10^-7 mol/L to 2.0×10^-5 mol/L, which crossed three orders of magnitude, and the detection limit was found 7.6×10^-5 mol/L （S/N=3）. In addition, the proposed sensor was successfully applied in determination of CF in drug sample.展开更多
Ionic liquid like 1-ethyl-3-methylimidazolium bromine ([EMIM]Br) has been used as electrolyte for the electropolymerization of O-phenylenediamine at glassy carbon electrode by cyclic voltammetry. It is found that poly...Ionic liquid like 1-ethyl-3-methylimidazolium bromine ([EMIM]Br) has been used as electrolyte for the electropolymerization of O-phenylenediamine at glassy carbon electrode by cyclic voltammetry. It is found that poly (O-phenylenediamine) film modified electrode has favorable electrochemical activity in acid solution.展开更多
The acid bio-leaching process of vanadium extraction from clay vanadium water-leached residue was studied and the effect of the performance of iron transformation was investigated.Acidithiobacillus ferrooxidans affect...The acid bio-leaching process of vanadium extraction from clay vanadium water-leached residue was studied and the effect of the performance of iron transformation was investigated.Acidithiobacillus ferrooxidans affects the dissolution of vanadium through the catalytic effect on Fe^3+/Fe^2+couple and material exchange.The passivation of iron settling correlates with ferrous ion content in bio-leaching solution.In medium containing A.ferrooxidans and Fe(Ⅲ),the increment in Fe(Ⅱ)concentration leads to the formation of jarosite,generating a decline in vanadium extraction efficiency.Analysis of cyclic voltammetry shows that Fe(Ⅱ)ion is apt to be oxidized and translated into precipitate by A.ferrooxidans,which strongly adsorbed to the surface of the residue.Fe(Ⅲ)ion promotes the vanadium extraction due to its oxidizing activity.Admixing A.ferrooxidans to Fe(Ⅲ)medium elevates the reduction of low valence state vanadium and facilitates the exchange of substance between minerals and solution.This motivates 3.8%and 21.8%increments in recovery ratio and leaching rate of vanadium compared to the Fe(Ⅲ)exclusive use,respectively.Moreover,Fe(Ⅱ)ion impacts vanadium extraction slightly in sterile medium but negatively influences vanadium leaching in the presence of bacteria.展开更多
The electrodeposition behavior of nickel at glassy carbon(GC)and stainless steel(SS)electrodes in low temperature urea-acetamide-NaBr-KBr melt was investigated using cyclic voltammetry,chrono-amperometric current-time...The electrodeposition behavior of nickel at glassy carbon(GC)and stainless steel(SS)electrodes in low temperature urea-acetamide-NaBr-KBr melt was investigated using cyclic voltammetry,chrono-amperometric current-time transients and scanning electron microscopy.Cyclic voltammograms and dimensionless chronoamperometric current-time transients analysis show that the electrodeposition of nickel is an irreversible process and proceeds via three-dimensional progressive nucleation with diffusion-controlled growth on both GC and SS substrates.Scanning electron microscopic analysis indicates the nickel deposits obtained on SS electrode are generally uniform,dense,and adherent to the substrate with rounded crystallites in the nanometer size regime.It is also found that the crystal structure of the electrodeposited nickel is independent on the deposition potential.The nickel deposits produced from the melt at higher cathodic potential exhibit larger grain size.展开更多
基金Projects(5110417951374247)supported by the National Natural Science Foundation of China
文摘In order to effectively separate galena and jamesonite and improve the recovery during the mixing flotation, the interaction mechanisms between the minerals and the collector of diethyl dithiocarbamate （DDTC） were investigated. Single mineral flotation test was organized to research the effect of pulp pH value on the flotation behavior of galena and jamesonite. Electrochemistry property of the interaction of these two minerals with DDTC was investigated by cyclic voltammetry and Tafel tests. Flotation test shows that the recovery of jamesonite in high alkaline pulp is strongly depressed by lime （Ca（OH）2）. The cyclic voltammetry and Tafel tests results show that the interaction between galena and DDTC is an electrochemical process. High pH value has little influence on the interaction between galena and DDTC, while it has great effect on jamesonite due to self-oxidation and specific adsorption of OH^- and CaOH^＋ on jamesonite surface. Non-electroactive hydroxyl compound and low-electroconductive calcium compounds cover the surface of jamesonite, which impedes electron transfer and DDTC adsorption, thus leads to very low floatability of jamesonite.
基金Project(21301193)supported by the National Nature Science Foundation of ChinaProject(2013M530356)supported by the China Postdoctoral Science Foundation Funded+1 种基金Project(CUSZC201303)supported by the Scientific Research Foundation of Central South Universitythe Open-End Found for Valuable and Precision Instruments of Central South University
文摘Electrochemical behavior of layered LiNi0.5Mn0.5O2 in LiNO3 aqueous solution and its cyclic fading mechanism in electrolytes with different pH values were investigated. CV results show that LiNi0.5Mn0.5O2 has good electrochemical reversible behaviors in 5 mol/L LiNO3 solution. Meanwhile, the electrode in 5 mol/L LiNO3 with pH value of 12 demonstrates the best electrochemical stability. Based on the electrochemical impedance spectroscopy （EIS）, X-ray diffraction （XRD） and scanning electron microscopy （SEM） results, it is proposed that suppressed charge-transfer resistance is the major reason, which is probably ascribed to the more stable electrode surface and less structure change.
基金Project(20976058)supported by the National Natural Science Foundation of China
文摘Growth and crystallization of titanium anodized films were studied by performing the anodization of the sputter-deposited titanium samples under cyclic voltammetry （CV） mode at very low potentials. The surface features, crystalline behaviors and chemical compositions of the formed anodic oxide layers were detected by AFM, SE and XPS. It was found that the structure of the titanium anodized films is crystalline, even though the maximum oxidation potential （（Pmax） is very low （as low as 1000 mY）. Both enlarging the applied voltage and reducing the potential scanning rate are beneficial for the growth and crystallization of titanium oxide films. It was thought that the internal compressive stress, other than the local joule heating accepted for many researchers, is the main force of stimulating the crystallization of anodic titanium oxide films at very low potentials.
文摘Aim To investigate the electrochemical behaviors of Mitomycin C （MC） and its interaction with calf thymus DNA （ctDNA）. Methods The cyclic vohammetry （CV） was carried out at a paraffined graphite electrode. Results MC showed a well-defined oxidation-reduction peak. As a result of reaction with ctDNA, the peak current of MC decreased apparently. According to corresponding electrochemical equations, the diffusion coefficient of both free and MC-DNA complex have been determined, and the heterogeneous rate constants were also obtained simultaneously. Conclusion The solid paraffined graphite electrode could be used to estimate parameters of the interaction between DNA and MC, and provide the convenient and sensitive analysis.
基金Project(2007CB613604)supported by the National Basic Research Program of China
文摘The electrodeposition of lead in alkaline solutions containing xylitol （1, 2, 3, 4, 5-pentahydroxypentane） was studied. The lead electrodeposition and the chemical stability of xylitol in alkaline solutions were investigated by cyclic voltammetry. Apparent activation energy, apparent transfer coefficient and exchange current density were obtained by linear sweep voltammetry. Initial stages of lead electrocrystallization were determined by chronoamperometry. Voltammograms of a AISI 316 stainless steel electrode in xylitol solution exhibit no current in the potential range of-1.3 V to 0.75 V （vs Hg/HgO）, implying that xylitol is stable to oxidation and reduction. The apparent activation energy, apparent transfer coefficient and exchange current density were calculated to be 35.15 kJ/mol, 1.56 and 9.65x10^-5 A/m^2. Analysis of the chronoamperometric responses implies three-dimensional growth of nuclei, with the type of nucleation depending on overpotential.
文摘Effects of meta-substituent of 3,4＇/4,3＇/3,3＇-substituted benzylideneanilines （XBAYs） on the electrochemical reduction potentials （E（Red）） were investigated, in which 49 samples of target compounds were synthesized, and their reduction potentials were measured by cyclic voltammetry. The substituent effects on the E（Red） of target compounds were analyzed and an optimality equation with four parameters （Hammett constant a of X, Hammett constant a of Y, excited-state substituent constant σexCC of X, and the substituent specific cross-interaction effect △σexCC2 between X and Y） was obtained. The results show that the factors affecting the E（Red） of 3,4＇/4,31/3,3P-substituted XBAYs are different from those of 4,4＇-substituted XBAYs. For 3,4＇/4,3＇/3,3＇-substituted XBAYs, σ（X） and σ（Y） must be employed, and the contribution of △σexCC2 is important and not negligible. Compared with 4,4＇-substituted XBAYs, X group contributes less to 3,4＇/4,3＇/3,3＇-substituted XBAYs, while Y group contributes more to them. Additionally, it was observed that either para-substituted XBAYs or meta-substituted XBAYs, the substituent effects of X are larger than those of Y on the E（Red） of substituted XBAYs.
基金Projects(N182503033N172502003)supported by the Fundamental Research Funds for the Central Universities,China+1 种基金Project(2018M640258)supported by Postdoctoral Research Foundation of ChinaProject(GUIKE AA18118030)supported by Guangxi Innovation-driven Development Program,China。
文摘To investigate the electrochemical reduction mechanism of Ta(Ⅴ)in ethylene carbonate and aluminum chloride(EC-AlCl3)solvate ionic liquid,cyclic voltammetry experiments were conducted on a tungsten working electrode.Four reduction peaks were observed in the cyclic voltammogram of the EC-AlCl3-TaCl5 ionic liquid.The reduction peaks at-0.55,-0.72,and-1.12 V(vs Al)were related to the reduction of Ta(Ⅴ)to tantalum metal by three stages including the formation of Ta(Ⅳ)and Ta(Ⅲ)complex ions.The reduction of Ta(Ⅲ)to tantalum metal was an irreversible diffusion-controlled reaction with a diffusion coefficient of 3.7×10^-7 cm^2/s at 323 K,and the diffusion activation energy was 77 k J/mol.Moreover,the cathode products at 323 K were characterized by scanning electron microscopy,energy-dispersive spectroscopy,and X-ray photoelectron spectroscopy.The results showed that tantalum metal and tantalum oxides were obtained by potentiostatic electrodeposition at-0.8 V for 2 h.
基金Ting-ting FENG acknowledges the financial support from Professor Paul V.BRAUN at Department of Materials Science and Engineering,University of Illinois at Urbana-Champaign,the support from Chinese Scholarship Council during her visit to University of Illinois at Urbana-Champaign,partial financial supports from Department of Science and Technology of Sichuan Province,China(2019YFH0002,2019YFG0222 and 2019YFG0526).The research was partly carried out in the Frederick Seitz Materials Research Laboratory Central Research Facilities,University of Illinois at Urbana-Champaign.
文摘The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 to 910 mA·h/g at 500 mA/g during 550 consecutive discharge/charge cycles,and delivers an ultrahigh capacity of 1276 mA·h/g at 100 mA/g,which is much greater than the theoretical capacity of either ZnMn2O4 or Mn3O4 electrode.To investigate the underlying mechanism of this phenomenon,cyclic voltammetry and differential capacity analysis were applied,both of which reveal the emergence and the growth of new reversible redox reactions upon charge/discharge cycling.The new reversible conversions are probably the results of an activation process of the electrode material during the cycling process,leading to the climbing charge storage.However,the capacity exceeding the theoretical value indicates that there are still other factors contributing to the increasing capacity.
基金financial supports from the National Natural Science Foundation of China(Nos.52004062,52074084,51804070)the Natural Science Foundation of Liaoning Province of China(No.2020-MS-084)the Guangxi Innovation-Driven Development Program,China(No.GUIKE AA18118030)。
文摘The density,conductivity,and viscosity of the 1,3-dimethyl-2-imidazolinone and lithium nitrate(DMILiNO_(3))solvated ionic liquid were measured as a function of temperature.Additionally,the electrochemical mechanism and electrodeposition of neodymium from the DMI-LiNO_(3) solvated ionic liquid were investigated.Cyclic voltammetry results indicate that the electrochemical reduction of Nd(Ⅲ)is irreversible and proceeds via one-step with three-electron transfer,which is controlled by diffusion with a diffusion coefficient of 5.08×10^(-8) cm^(2)/s.Energydispersive X-ray spectrometry and X-ray photoelectron spectroscopy data confirm that the electrodeposit obtained after electrodeposition at-4 V(vs Ag)using the DMI-LiNO_(3)-Nd(CF_(3)SO_(3))_(3) solvated ionic liquid contains metallic neodymium.
文摘In this article, the electrochemical performance of the electrodes of zinc polycrystal, Zn（002） and Zn（100） single crystals were studied by the Tafel line extrapolation of the potentio-dynamic polarization curves, the cyclic voltammetry and the charge/discharge experiment. The results shows that in 6.0 mol·L^-1 KOH solution the corrosion rate of Zn polycrystal, Zn（100） and Zn（002） single crystals decreases in turn; and the reversibility and the charge/discharge performance of Zn single crystal was superior to Zn polycrystal. The dendrite growth of the surface of Zn polycrvstal was easier than Zn single crystal during the stages of charge/discharge.
基金The authors are grateful for the financial supports from the Fundamental Research Funds for the Central Universities,China(N182503033,N172502003)Postdoctoral Research Foundation of China(2018M640258)+1 种基金the National Natural Science Foundation of China(51804070)Guangxi Innovation-driven Development Program,China(GUIKE AA18118030).
文摘Zinc chloride(ZnCl_(2))was dissolved in the 1,3-dimethyl-2-imidazolinone(DMI)solvent,and the metallic zinc coatings were obtained by electrodeposition in room-temperature ambient air.The conductivity(σ),viscosity(η),and density(ρ)of the DMI−ZnCl_(2)solvated ionic liquid at various temperatures(T)were measured and fitted.Furthermore,cyclic voltammetry was used to study the electrochemical behavior of Zn(II)in the DMI−ZnCl_(2)solvated ionic liquid,indicating that the reduction of Zn(II)on the tungsten electrode was a one-step two-electron transfer irreversible process.XRD and SEM−EDS analysis of the cathode product confirmed that the deposited coating was metallic zinc.Finally,the effects of deposition potential,temperature and duration on the morphology of zinc coatings were investigated.The results showed that a dense and uniform zinc coating was obtained by potentiostatic electrodeposition at−2 V(vs Pt)and 353 K for 1 h.
基金Projects(51074185, 51274240) supported by the National Natural Science Foundation of ChinaProject supported by the Fundamental Research Funds for the Central Universities
文摘Alloy anodes were studied for pursuing Sn-based microcomposite synthesis, assembly and performance for lithium ion batteries. The self-assembled Sn-Co-C composites with nano-scaled microstructures were prepared via solution method and carbothermal technology. The morphology and physical structure were investigated with scanning electron microscope (SEM) and X-ray diffraction (XRD). The as-prepared materials were assembled to half cell coin for the purpose of discussing the galvanostatic cycling, cyclic voltammetry and rate-capability performance. Results reveal that nanoscaled CoSn 2 alloys covered with Sn and C layer by layer are wrapped by cross-linked porous carbon network to form spherical microstructure. This distinguishing feature of Sn-Co-C composites provides a possible solution to the problems of Sn particle aggregation and poor electron transport, and has strong effect on improving electrochemical performance.
基金Projects(51204080, 51274108) supported by the National Natural Science Foundation of ChinaProject(2011FA009) supported by the Natural Science Foundation of Yunnan Province, ChinaProject(2011FZ020) supported by the Application Research Foundation of Yunnan Province, China
文摘The effect of two alkylpyridinium ionic liquids （py-iLs） including N-butylpyridinium hydrogen sulfate （BpyHSO4） and N-hexylpyridinium hydrogen sulfate （HpyHSO4） on the kinetics of copper electrodeposition from acidic sulfate solution was investigated by cyclic voltammetry and potentiodynamic polarization measurements. Results from cyclic voltammetry indicate that these py-iLs have a pronounced inhibiting effect on CuE＋ electroreduction and there exists a typical nucleation and growth process. Kinetic parameters such as Tafel slope, transfer coefficient and exchange current density obtained from Tafel plots, lead to the conclusion that py-iLs inhibit the charge transfer by slightly changing the copper electrodeposition mechanism through their adsorption on the cathodic surface. In addition, scanning electron microscope （SEM） and X-ray diffraction analyses reveal that the presence of these additives leads to more leveled and fine-grained cathodic deposits without changing the crystal structure of the electrodeposited copper but strongly affects the crystallographic orientation by significantly inhibiting the growth of （111）, （200） and （311） planes.
基金Project(201215135) supported by the Natural Science Foundation of Jilin Province,China
文摘The novel covalently modified glassy carbon electrode with poly(xylitol) was prepared using an electropolymerization technique for the simultaneous determination of uric acid(UA), xanthine(XA) and hypoxanthine(HX). This new electrode presents an excellent electrocatalytic activity towards the oxidation of UA, XA and HX by cyclic voltammetry(CV) method. The oxidation peaks of the three compounds were well defined and had enhanced the peak currents. The separation potentials of the oxidation peak potentials for UA-XA and XA-HX were 380 and 370 mV in CV, respectively. Using differential pulse voltammetry(DPV) method, the calibration curves in the ranges of 5-55, 1.3-75.3 and 4-59 μmol/L were obtained for HX, XA and UA, respectively. The lowest detection limits(S/N=3) were 4.5, 0.75 and 3.75 μmol/L for HX, XA and UA, respectively. The practical application of the modified electrode was demonstrated by the determination of UA, XA, HX in human urine samples.
基金Project(KJ2012A045) supported by the Natural Science Foundation of Education Commission of Anhui Province,China
文摘A reduced graphene oxide/Ni(OH)2 composite with excellent supercapacitive performance was synthesized by a facile hydrothermal route without organic solvents or templates used.XRD and SEM results reveal that the nickel hydroxide,which crystallizes into hexagonal β-Ni(OH)2 nanoflakes with a diameter less than 200 nm and a thickness of about 10 nm,is well combined with the reduced graphene oxide sheets.Electrochemical performance of the synthesized composite as an electrode material was investigated by cyclic voltammetry,electrochemical impedance spectroscopy and galvanostatic charge/discharge measurements.Its specific capacitance is determined to be 1672 F/g at a scan rate of 2 mV/s,and 696 F/g at a high scan rate of 50 mV/s.After 2000 cycles at a current density of 10 A/g,the composite exhibits a specific capacitance of 969 F/g,retaining about 86% of its initial capacitance.The composite delivers a high energy density of 83.6 W·h/kg at a power density of 1.0 kW/kg.The excellent supercapacitive performance along with the easy synthesis method allows the synthesized composite to be promising for supercapacitor applications.
文摘Carboxyl graphene modified CuxO/Cu electrode was fabricated. The bare copper electrode was firstly anodic polarized in 1.0 mol/L NaOH solution in order to get CuxO nanoparticles, then the carboxyl graphene （CG） was electrodeposited on the CuxO/Cu electrode by cyclic potential sweeping. The electrocatalytic oxidation behaviors of calcium folinate （CF） at the graphene modified CuxO/Cu electrode were investigated by cyclic voltammetry. A positive scan polarization reverse catalytic voltammetry was used to obtain the pure catalytic oxidation current. The graphene modified CuxO/Cu electrode was served as the electrochemical sensor of CF, a highly sensitivity of 22.0μA.（μmol/μL）^-1cm^-2 was achieved, and the current response was linear with increasing CF concentration in the range of 2.0×10^-7 mol/L to 2.0×10^-5 mol/L, which crossed three orders of magnitude, and the detection limit was found 7.6×10^-5 mol/L （S/N=3）. In addition, the proposed sensor was successfully applied in determination of CF in drug sample.
文摘Ionic liquid like 1-ethyl-3-methylimidazolium bromine ([EMIM]Br) has been used as electrolyte for the electropolymerization of O-phenylenediamine at glassy carbon electrode by cyclic voltammetry. It is found that poly (O-phenylenediamine) film modified electrode has favorable electrochemical activity in acid solution.
基金Project(DY135-B2-15) supported by the China Ocean Mineral Resource R&D AssociationProject(2015ZX07205-003) supported by Major Science and Technology Program for Water Pollution Control and Treatment,ChinaProjects(21176242,21176026) supported by the National Natural Science Foundation of China
文摘The acid bio-leaching process of vanadium extraction from clay vanadium water-leached residue was studied and the effect of the performance of iron transformation was investigated.Acidithiobacillus ferrooxidans affects the dissolution of vanadium through the catalytic effect on Fe^3+/Fe^2+couple and material exchange.The passivation of iron settling correlates with ferrous ion content in bio-leaching solution.In medium containing A.ferrooxidans and Fe(Ⅲ),the increment in Fe(Ⅱ)concentration leads to the formation of jarosite,generating a decline in vanadium extraction efficiency.Analysis of cyclic voltammetry shows that Fe(Ⅱ)ion is apt to be oxidized and translated into precipitate by A.ferrooxidans,which strongly adsorbed to the surface of the residue.Fe(Ⅲ)ion promotes the vanadium extraction due to its oxidizing activity.Admixing A.ferrooxidans to Fe(Ⅲ)medium elevates the reduction of low valence state vanadium and facilitates the exchange of substance between minerals and solution.This motivates 3.8%and 21.8%increments in recovery ratio and leaching rate of vanadium compared to the Fe(Ⅲ)exclusive use,respectively.Moreover,Fe(Ⅱ)ion impacts vanadium extraction slightly in sterile medium but negatively influences vanadium leaching in the presence of bacteria.
基金Supported by the National Natural Science Foundation of China（51204080,51274108,21263007） the Natural Science Foundation of Yunnan Province（2011FA009）,and the Application Foundation Research of Yunnan Province（2011FZ020）
文摘The electrodeposition behavior of nickel at glassy carbon(GC)and stainless steel(SS)electrodes in low temperature urea-acetamide-NaBr-KBr melt was investigated using cyclic voltammetry,chrono-amperometric current-time transients and scanning electron microscopy.Cyclic voltammograms and dimensionless chronoamperometric current-time transients analysis show that the electrodeposition of nickel is an irreversible process and proceeds via three-dimensional progressive nucleation with diffusion-controlled growth on both GC and SS substrates.Scanning electron microscopic analysis indicates the nickel deposits obtained on SS electrode are generally uniform,dense,and adherent to the substrate with rounded crystallites in the nanometer size regime.It is also found that the crystal structure of the electrodeposited nickel is independent on the deposition potential.The nickel deposits produced from the melt at higher cathodic potential exhibit larger grain size.
