Copper patinas are generally regarded as aesthetically pleasing and are supposed to protect copper against further corrosion. The preparation of artificial sulphate patina on bronzes has been realized by immersing the...Copper patinas are generally regarded as aesthetically pleasing and are supposed to protect copper against further corrosion. The preparation of artificial sulphate patina on bronzes has been realized by immersing the bronze into CuSO4 solution. The effect of immersion time on the formation of the patina has been investigated. The sulphate patina obtained with immersion time of 500 h in CuSO4 solution consists of fiat area and crystals. The flat area in the patina is mainly made of cuprite, whereas the crystals are mainly composed of brochantite. The electrochemical measurement of sulphate patina in simulated acid rain with pH 3.1 shows that the protective effectiveness of patina decreases with time and the dissolution of patina is the key factor leading to the degradation of patina. The investigation of the formation mechanism of sulphate patina shows that the cuprite layer forms on the surface of bronze in the initial patination. Then, crystal brochantite grows on the surface of cuprite by the oxidation of cuprite and the incorporation of CuSO4 solution.展开更多
The redox behaviours of a donor-acceptor model compound. p-tricyano-ethenyl-N, N-dimethyl aniline was investigated by electrochemical and spectroelectrochemical methods. The results indicate that charge transfer betwe...The redox behaviours of a donor-acceptor model compound. p-tricyano-ethenyl-N, N-dimethyl aniline was investigated by electrochemical and spectroelectrochemical methods. The results indicate that charge transfer between the donor(amino) and the acceptor(cyanoethenyl) groups takes place in the process of oxidation of this compound.展开更多
This work focused on the role of Al_(2)O_(3) particles in the corrosion behavior of cold sprayed AA5083 aluminum alloy matrix composite(Al-MMC)coatings.The electrochemical characterization of the coatings was investig...This work focused on the role of Al_(2)O_(3) particles in the corrosion behavior of cold sprayed AA5083 aluminum alloy matrix composite(Al-MMC)coatings.The electrochemical characterization of the coatings was investigated in a 3.5 wt.%NaCl solution as a function of time.The results show that fragmentation of Al_(2)O_(3) particles is not clearly observed in the case of AA5083/20 vol.%Al_(2)O_(3) coating,while the broken Al_(2)O_(3) particles can be seen clearly in AA5083/40 vol.%Al_(2)O_(3) and AA5083/60 vol.%Al_(2)O_(3) coatings.The addition of 20 vol.%Al_(2)O_(3) particles yield the coating with the lowest porosity,and different volume fractions of Al_(2)O_(3)in the feedstock have important effects on the electrochemical behavior of composite coatings.The Al-MMC coating reinforced with 20 vol.%Al_(2)O_(3) particles exhibits the highest Ecorrand the lowest icorrcompared with the other conditions.The order of current density is as follows:AA5083/20vol.%Al_(2)O_(3)<AA5083<AA5083/40 vol.%Al_(2)O_(3)<AA5083/60 vol.%Al_(2)O_(3).展开更多
The development of novel organic electrode materials is of great significance for improving the reversible capacity and cycle stability of rechargeable batteries.Before practical application,it is essential to charact...The development of novel organic electrode materials is of great significance for improving the reversible capacity and cycle stability of rechargeable batteries.Before practical application,it is essential to characterize the electrode materials to study their structures,redox mechanisms and electrochemical performances.In this review,the common characterization methods that have been adopted so far are summarized from two aspects:experimental characterization and theoretical calculation.The experimental characterization is introduced in detail from structural characterization,electrochemical characterization and electrode reaction chara cterization.The experimental purposes and working principles of various experimental characterization methods are briefly illustrated.As the auxilia ry means,theoretical calculation provides the theoretical basis for characterizing the electrochemical reaction mechanism of organic electrode materials.Through these characterizations,we will have a deep understanding about the material structures,electrochemical redox mechanisms,electrochemical properties and the relationships of structure-property.It is hoped that this review would help researchers to select the suitable characterization methods to analyze the structures and performances of organic electrode materials quickly and effectively.展开更多
Polyelectrolyte becomes more and more popular in electrocatalysis.The understanding of electrode/polyelectrolyte interfaces at the molecular level is important for guiding further the polyelectrolyte-based electrocata...Polyelectrolyte becomes more and more popular in electrocatalysis.The understanding of electrode/polyelectrolyte interfaces at the molecular level is important for guiding further the polyelectrolyte-based electrocatalysis.Herein,we demonstrate an in-situ surface-enhanced Raman spectroscopic method by using a three-electrode spectroelectrochemical cell towards characterizing the electrode/polyelectrolyte interfaces.The Ag/AgCl and Ag/Ag_(2)O electrodes are used as the reference electrode in the acidic and the alkaline systems,respectively.The working electrode is made of a transparent carbon thin film which loads the electrocatalysts.The applications of this method are demonstrated through the in-situ characterizations of the p-methylthiophenol adsorbed on the Au and Pt and the electrochemical oxidation of Au on polyelectrolyte membranes.The potential-dependent spectral features of these two systems show that this method is a powerful tool for investigating the electrode/polyelectrolyte interfaces in electrocatalysis.展开更多
Electrochemical characteristics of covellite (CuS) are of importance from flotation and metallurgical point of view, as well as due to its potential application in solid state solar cells and in photocatalytic reactio...Electrochemical characteristics of covellite (CuS) are of importance from flotation and metallurgical point of view, as well as due to its potential application in solid state solar cells and in photocatalytic reactions. Also, the compound CuS appears as an intermediary product or a final product in electrochemical oxidation reactions of chalcocite (Cu2S) which exhibits supercapacitor characteristics. Natural copper mineral covellite has been investigated in inorganic sulfate acid electrolytes, as well as in strong alkaline electrolyte. Physical properties of covellite were characterized by X-ray diffraction (XRD) and the active surface was examined by optical and electron microscopy (EM) before and after oxidation in galvanostatic regime. Different electrochemical methods (galvanostatic, potentiostatic, cyclic voltammetry and electrochemical impedance spectroscopy - EIS) have been used. The capacitance of around 21 Fcm-2 (geometric area), serial resistance of about 90 Ωcm2 and leakage resistance of about 1200 Ωcm2 have been measured in 1 M H2SO4. The addition of cupric ions in sulfate electrolyte leads to the significant increasing of the capacitance, but having the increase of self-discharge as a negative side phenomenon. The capacitance of around 6.7 Fcm-2 (geometric area), serial resistance of about 80 Ωcm2 and leakage resistance of about 380 Ωcm2 have been measured in 6 M KOH.展开更多
Since the 1980s,single-crystal Pt electrodes with well-defined surface structures have been deemed stable under mild electrochemical conditions(e.g.,in the potential region of electric double layers,underpotential dep...Since the 1980s,single-crystal Pt electrodes with well-defined surface structures have been deemed stable under mild electrochemical conditions(e.g.,in the potential region of electric double layers,underpotential deposition of hydrogen,or mild hydrogen evolution/OH adsorption)and have served as model electrodes for unraveling the structure-performance relation in electrocatalysis.With the advancement of in situ electrochemical microscopy/spectroscopy techniques,subtle surface restructuring under mild electrochemical conditions has been achieved in the last decade.Surface restructuring can considerably modify electrocatalytic properties by generating/destroying highly active sites,thereby interfering with the deduction of the structure-performance relation.In this review,we summarize recent progress in the restructuring of well-defined Pt(-based)electrode surfaces under mild electrochemical conditions.The importance of the meticulous structural characterization of Pt electrodes before,during,and after electrochemical measurements is demonstrated using CO adsorption/oxidation,hydrogen adsorption/evolution,and oxygen reduction as examples.The implications of present findings for correctly identifying the reaction mechanisms and kinetics of other electrocatalytic systems are also briefly discussed.展开更多
To improve the electrochemical performances of α-MnO2 as electrode materials for supercapacitors, Sn-doped α-MnO2 in the presence of the doping amount of 1%-4% was successfully synthesized by hydrothermal method. As...To improve the electrochemical performances of α-MnO2 as electrode materials for supercapacitors, Sn-doped α-MnO2 in the presence of the doping amount of 1%-4% was successfully synthesized by hydrothermal method. As-prepared α-MnO2 presents nanorod shape and no other impurities exist. By ultraviolet-visible absorption spectroscopy, it is convinced that the band gaps of α-MnO2 decrease with increasing Sn-doping amount. Cyclic voltammetry investigation indicates that undoped and doped α-MnO2 all have regular capacitive response. As the scan rate enlarged, the profiles of curves gradually deviate from rectangle. Compared with undoped α-MnO2, doped α-MnO2 has larger specific capacitance. The specific capacitance of 3% doped α-MnO2 reaches 241.0 F/g while undoped α-MnO2 only has 173.0 F/g under 50 m A/g current density in galvanostatical charge-discharge measurement. Enhanced conductivity by Sn-doping is considered to account for doped sample＇s enhanced electrochemical specific capacitance.展开更多
An investigation into the corrosion characteristics and mechanism of directionally solidified(DSed) Mg-3Zn-xCa(x = 0, 0.2, 0.5,0.8 wt.%) alloys in 0.9 wt.% Na Cl solution is presented. The DSed microstructure consists...An investigation into the corrosion characteristics and mechanism of directionally solidified(DSed) Mg-3Zn-xCa(x = 0, 0.2, 0.5,0.8 wt.%) alloys in 0.9 wt.% Na Cl solution is presented. The DSed microstructure consists of columnar dendrites and eutectics distributed in the interdendritic region. The primary dendritic arm spacing(PDAS) and the volume fraction(fv) of the secondary phases are under the significant impact of the content of Ca. The corrosion rates evaluated using electrochemical measurements and immersion tests are accelerated monotonously with the increase of Ca content in DSed alloys. The corrosion resistance of the DSed alloys is significantly affected by the corrosion products film(CPF) and the secondary phases. The corrosion products of DSed Mg-3Zn alloy contain Mg(OH)_(2) and ZnO. The existence of ZnO greatly enhances the corrosion resistance of DSed Mg-3Zn alloy. As for the DSed alloys containing Ca content, a relatively protective CPF without deep pits can form on the surface of DSed Mg-3Zn-0.2Ca specimen during the corrosion. The f_(v)of the secondary phases dominates the corrosion rate of the DSed Mg-Zn-Ca alloys. The corrosion of DSed Mg-3Zn-xCa alloys initiates as a result of microgalvanic coupling between the cathodes of secondary phases and α-Mg matrix anode. Then, the corrosion gradually extends longitudinally with the breakdown of CPF.展开更多
A series of electrochemical and long-term corrosion tests were carried out in a neutral saline （5%NaCl） vapor of 35 °C on thermal sprayed WC cermet coatings containing different kinds of metallic binders in ord...A series of electrochemical and long-term corrosion tests were carried out in a neutral saline （5%NaCl） vapor of 35 °C on thermal sprayed WC cermet coatings containing different kinds of metallic binders in order to examine the effect of composition of binder materials on the corrosion behavior. The experimental results revealed that the overall corrosion resistance of WC-Co coating was inferior to that of WC-Co-Cr coating. For the coatings without Cr, WC-Co, general corrosion occurred in binder materials in addition to galvanic corrosion between WC particles and metallic binders in the neutral environment. By contrast, the formation of passive film in the form of surface oxide in the coatings containing Cr, WC-Co-Cr, suppressed the binder and metallic binders to be eroded. It is found that the chemical composition of metallic binder materials is one of the important factors influencing the corrosion resistance of HVOF sprayed WC cermet coatings in the neutral vapor.展开更多
The corrosion behavior of Mg-10Gd-xZn(x=2,6 wt.%)alloys in 0.5 wt.%NaCl solution was investigated.Microstructures of both the alloys consisted of(Mg,Zn)_(3) Gd phase and lamellar long period stacking ordered(LPSO)phas...The corrosion behavior of Mg-10Gd-xZn(x=2,6 wt.%)alloys in 0.5 wt.%NaCl solution was investigated.Microstructures of both the alloys consisted of(Mg,Zn)_(3) Gd phase and lamellar long period stacking ordered(LPSO)phase.The morphology of the second phase at the grain boundary differed in both alloys:it was a continuous network structure in Mg-10Gd-6Zn,whereas it was relatively discrete in Mg-10Gd-2Zn.The dendrites were finer in size and highly branched in Mg-10Gd-6Zn.The corrosion results indicated that the increase in Zn content increased the corrosion rate in Mg-10Gd-xZn alloys.Micro-galvanic corrosion occurred near the grain boundary in both alloys initially as the grain boundary phase was stable and acted as a cathode,however,filiform corrosion dominated in the later stage,which was facilitated by the LPSO phase in the matrix.Severe micro-galvanic corrosion occurred in Mg-10Gd-6Zn due to the higher volume of second phase.The stability of the second phase at the grain boundary was altered and dissolved after the long immersion times.Probably the NaCl solution chemically reacted with the grain boundary phase and de-stabilized it during the long immersion times,and was removed by the chromic acid used for the corrosion product removal.展开更多
The use of magnesium alloys,as a biodegradable medical device,is an interesting challenge for the biomaterials field.Its rapid degradation and the release of hydrogen,when exposed to biological fluids,are the main dra...The use of magnesium alloys,as a biodegradable medical device,is an interesting challenge for the biomaterials field.Its rapid degradation and the release of hydrogen,when exposed to biological fluids,are the main drawbacks for clinical applications.In this work,a coating made of polydopamine(PDOPA),is used as an intermediate layer to decrease the degradation rate of AZ31 magnesium alloy/polymeric coating system,when exposed to Hank’s solution.Experimental results highlighted:(i)the formation of a thin PDOPA layer,(ii)an increased adhesion in the organic coating/metallic substrate system,(iii)a decrease of two orders of magnitude of the corrosion rate when the PDOPA film is used together with an external organic coating,(iv)the efficacy in the use of PDODA due to the synergistic effect of both,physical and chemical,interactions between the PDOPA layer and the organic coating.展开更多
Magnesium alloys are candidates as biodegradable medical materials due to their biocompatibility and favorable mechanical properties.Unfortunately,the high corrosion rate in physiological media and the release of hydr...Magnesium alloys are candidates as biodegradable medical materials due to their biocompatibility and favorable mechanical properties.Unfortunately,the high corrosion rate in physiological media and the release of hydrogen,limit their widespread use in biomedical applications.In this work,an intermediate coating based on polydopamine(PDOPA),between Mg substrate and an organic coating,was used to decreasing the degradation rate of AZ31 magnesium alloy,during the long-term exposure in simulated body fluid.Electrochemical Impedance Spectroscopy measurements were carried out to study the corrosion resistance of samples.Results demonstrated that the PDOPA interlayer determined the reduction of the substrate degradation rate.The results were interpreted supposing a synergistic effect which occurred when PDOPA and the organic coating were used together.展开更多
Dye-sensitized solar cell （DSSC） is one of the most rapidly developed solar cells in the past 20 years. Many characterization methods have been employed for further understanding the operational details of the photo...Dye-sensitized solar cell （DSSC） is one of the most rapidly developed solar cells in the past 20 years. Many characterization methods have been employed for further understanding the operational details of the photo- electric conversion in DSSC as well as the evaluation of cell performance. Electrochemical methods have become pow- erful tools for studying the charge transfer and interfacial process. In this review, we introduce and explain the various electrochemical methods used to characterize and analyze DSSC, including current-voltage （I-V） scan measurement, cyclic voltammetry, electrochemical impedance spec- troscopy, intensity-modulated photocurrent spectroscopy, and intensity-modulated photovoltage spectroscopy. In ad- dition, some applications were provided as samples to elucidate electron transfer kinetics, energy levels and electrocatalytic activity of the materials used in DSSC.展开更多
Electrochemical oxidation of diphenylamine(DPA)in acetonitrile solution produced an adhesive conducting polydiphenylamine(PDPA)film on the electrode,which exhibited multiple colour variation in a wide range of potenti...Electrochemical oxidation of diphenylamine(DPA)in acetonitrile solution produced an adhesive conducting polydiphenylamine(PDPA)film on the electrode,which exhibited multiple colour variation in a wide range of potential.The polymer was characterized by cyclic voltam- merry,FTIR and ESR.The results indicate that the electropolymerization of diphenylamine per- forms via the 4,4＇C—C phenyl-phenyl coupling mechanism.FTIR,ESR and conductivity mea- surements for the different states of PDPA show that polydiphenylamine can be reversibly doped and dedoped either chemically or electrochemically.It is evidenced also that there are paramagnetic species—polarons in PDPA supposed to be the current carrier.展开更多
The layered material of Ce-doped LiNi1/3Mn1/3Co1/3O2 with α-NaFeO2 was synthesized by a co-precipitation method. X-ray diffraction （XRD） showed that Ce-doped LiNi1/3Mn1/3Co1/3O2 had the same layered structure as th...The layered material of Ce-doped LiNi1/3Mn1/3Co1/3O2 with α-NaFeO2 was synthesized by a co-precipitation method. X-ray diffraction （XRD） showed that Ce-doped LiNi1/3Mn1/3Co1/3O2 had the same layered structure as the undoped LiNi1/3Mn1/3Co1/3O2. The scanning electron microscopy （SEM） images exhibited that the particle size of Ce-doped LiNi1/3Mn1/3Co1/3O2 was smaller than that of the undoped LiNi1/3Mn1/3Co1/3O2. The Ce-doped LiNi1/3Mn1/3Co1/3O2 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram （CV）, and electrochemical impedance spectra （EIS）. The optimal doping content of Ce was x=0.02 in the LiNi1/3-xMn1/3Co1/3CexO2 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through Ce-doping. The improved electrochemical performances of the Ce-doped LiNi1/3Mn1/3Co1/3O2 cathode materials were attributed to the addition of Ce4＋ ion by stabilizing the layer structure.展开更多
This paper mainly clarified the dispersion mechanism of three typical chemical dispersants which are polyethylene glycol octylphenyl ether(Triton X-100,T-100),polyethylene pyrrolidone(PVP)and carboxymethyl cellulose(C...This paper mainly clarified the dispersion mechanism of three typical chemical dispersants which are polyethylene glycol octylphenyl ether(Triton X-100,T-100),polyethylene pyrrolidone(PVP)and carboxymethyl cellulose(CMC)within lithium-ion battery(LIB)slurry.Initially,the optimum amounts of T-100,PVP and CMC are selected from 0%,0.5%,1.5%and 2.5%by evaluating the impedance of LIB slurry in the case of adding each typical chemical dispersant with EIS method.Moreover,the impedance spectrum of three different slurry samples which are PVDF-NMP solution,LiCoO_(2) slurry and Carbon Black(CB)slurry with the optimum amount of each dispersant are also investigated.After using SEM and C element distribution images of LIB slurry to verify the correctness of the dispersion mechanism of each dispersant,it is concluded that the dispersion CMC with its optimum amount 1.5%is the best one to promote the formation of conductive paths and CB-coated LiCoO_(2) network structure within LIB slurry,which has the considerably potential to improve the performance of LIB.展开更多
The effect of residual dissolved oxygen （DO） on the corrosion behavior of carbon steel in 0.1 M NaHCO3 solution was investigated by electrochemical measurements, corrosion mass loss test, scanning electron microsco...The effect of residual dissolved oxygen （DO） on the corrosion behavior of carbon steel in 0.1 M NaHCO3 solution was investigated by electrochemical measurements, corrosion mass loss test, scanning electron microscopy （SEM） and X-ray diffraction （XRD）. In the initial immersion stage, the increase of the dissolved oxygen concentration led to the change of from a reductive state of active dissolution to an oxidizing state of pseudo passivation in low carbon steel. While in the final stage, all the steels transformed into the steady state of pseudo passivation. In the anaerobic solution, the formation of c^-FeOOH was attributed to the chemical oxidization of the ferrous corrosion products and the final cathodic process only included the reduction of c^-FeOOH, while in the aerobic solution, it included the reduction of oxygen and （x-FeOOH simultaneously. As the main corrosion products, the content of （x-FeOOH was increased while that of Fe6（OH）12CO3 was decreased with increasing concentration of dissolved oxygen. The total corrosion mass loss of the steel was promoted with the increase of dissolved oxygen concentration.展开更多
Low-Co Lal.8Ti0.2MgNi8.9Co0.1 alloys were prepared by magnetic levitation melting followed by annealing treatment. The effect of annealing on the hydrogen storage properties of the alloys was investigated systematical...Low-Co Lal.8Ti0.2MgNi8.9Co0.1 alloys were prepared by magnetic levitation melting followed by annealing treatment. The effect of annealing on the hydrogen storage properties of the alloys was investigated systematically by X-ray diffraction （XRD）, pressure-com- position isotherm （PCI）, and electrochemical measure- ments. The results show that all samples contain LaNi5 and LaMg2Ni9 phases. LaCo5 phase appears at 1,000 ℃. The enthalpy change of all hydrides is close to -30.6 kJ.mo1-1 H2 of LaNi5 compound. Annealing not only increases hydrogen capacity and improves cycling stability but also decreases plateau pressure at 800 and 900 ℃. After annealing, the contraction of cell volume and the increase of hydride stability cause the high rate dischargeability to reduce slightly. The optimum alloy is found to be one annealed at 900 ℃, with its hydrogen capacity reaching up to 1.53 wt%, and discharge capacity remaining 225.1 mAh·g-1 after 140 charge-discharge cycles.展开更多
The effect of the rare earth element Er on the microstructures and properties of Mg-Al intermetallic were studied in this experiment. Metallographic and X-ray diffraction（XRD） results showed that the microstructures...The effect of the rare earth element Er on the microstructures and properties of Mg-Al intermetallic were studied in this experiment. Metallographic and X-ray diffraction（XRD） results showed that the microstructures of Mg-Al-Er alloys varied with Er content. The Mg-44Al-0.5Er and Mg-43.8Al-1.0Er alloys were both composed of Mg17Al12 matrix and Al3 Er phase, whereas Mg-43Al-3.0Er and Mg-42Al-5.0Er were composed of Mg17Al12 matrix, Al3 Er phase, and Mg-Mg17Al12 eutectic. The Mg-42Al-5.0Er alloy showed the highest microhardness, and the values remained nearly stable as Er content increased from 1.0 wt.% to 5.0 wt.%. The dispersed second phase Al3 Er caused the grain refinement of the Mg-Al-Er alloy, which was the main reason for the improvement in microhardness. The corrosion resistance of the Er-containing alloys initially increased and then decreased with increasing Er content. All the Er-containing alloys had the ability to suppress hydrogen evolution, which was the main reason for the higher corrosion resistance of the modified alloys than that of the Mg-44.3Al alloy. Considering the higher hardness and dispersity of the Al3 Er phase, Mg-43.8Al-1.0Er exhibited higher wear resistance than the as-cast Mg-44.3Al alloy.展开更多
基金Funded by the Special Fund for Talent of Wuhan Instituteof Technologythe Fellowship for Junior Researchers fromPolitecnico di Torino and Regione Piemonte,Italy
文摘Copper patinas are generally regarded as aesthetically pleasing and are supposed to protect copper against further corrosion. The preparation of artificial sulphate patina on bronzes has been realized by immersing the bronze into CuSO4 solution. The effect of immersion time on the formation of the patina has been investigated. The sulphate patina obtained with immersion time of 500 h in CuSO4 solution consists of fiat area and crystals. The flat area in the patina is mainly made of cuprite, whereas the crystals are mainly composed of brochantite. The electrochemical measurement of sulphate patina in simulated acid rain with pH 3.1 shows that the protective effectiveness of patina decreases with time and the dissolution of patina is the key factor leading to the degradation of patina. The investigation of the formation mechanism of sulphate patina shows that the cuprite layer forms on the surface of bronze in the initial patination. Then, crystal brochantite grows on the surface of cuprite by the oxidation of cuprite and the incorporation of CuSO4 solution.
文摘The redox behaviours of a donor-acceptor model compound. p-tricyano-ethenyl-N, N-dimethyl aniline was investigated by electrochemical and spectroelectrochemical methods. The results indicate that charge transfer between the donor(amino) and the acceptor(cyanoethenyl) groups takes place in the process of oxidation of this compound.
基金financially supported by the authors would like to acknowledge the National Key Research and Development Program of China(No.2016YFB1100104)the National Natural Science Foundation of China(No.51875470)+1 种基金the State Key Laboratory of Solidification Processing(NPU,China)(No.2019-QZ-01)the financial support from the fund of SAST(No.SAST2016043)。
文摘This work focused on the role of Al_(2)O_(3) particles in the corrosion behavior of cold sprayed AA5083 aluminum alloy matrix composite(Al-MMC)coatings.The electrochemical characterization of the coatings was investigated in a 3.5 wt.%NaCl solution as a function of time.The results show that fragmentation of Al_(2)O_(3) particles is not clearly observed in the case of AA5083/20 vol.%Al_(2)O_(3) coating,while the broken Al_(2)O_(3) particles can be seen clearly in AA5083/40 vol.%Al_(2)O_(3) and AA5083/60 vol.%Al_(2)O_(3) coatings.The addition of 20 vol.%Al_(2)O_(3) particles yield the coating with the lowest porosity,and different volume fractions of Al_(2)O_(3)in the feedstock have important effects on the electrochemical behavior of composite coatings.The Al-MMC coating reinforced with 20 vol.%Al_(2)O_(3) particles exhibits the highest Ecorrand the lowest icorrcompared with the other conditions.The order of current density is as follows:AA5083/20vol.%Al_(2)O_(3)<AA5083<AA5083/40 vol.%Al_(2)O_(3)<AA5083/60 vol.%Al_(2)O_(3).
基金the financial support of the National Natural Science Foundation of China(Nos.21875206,21403187)the Natural Science Foundation of Hebei Province(No.B2019203487)the open project in Key Lab Adv.Energy Mat.Chem.(Nankai University)。
文摘The development of novel organic electrode materials is of great significance for improving the reversible capacity and cycle stability of rechargeable batteries.Before practical application,it is essential to characterize the electrode materials to study their structures,redox mechanisms and electrochemical performances.In this review,the common characterization methods that have been adopted so far are summarized from two aspects:experimental characterization and theoretical calculation.The experimental characterization is introduced in detail from structural characterization,electrochemical characterization and electrode reaction chara cterization.The experimental purposes and working principles of various experimental characterization methods are briefly illustrated.As the auxilia ry means,theoretical calculation provides the theoretical basis for characterizing the electrochemical reaction mechanism of organic electrode materials.Through these characterizations,we will have a deep understanding about the material structures,electrochemical redox mechanisms,electrochemical properties and the relationships of structure-property.It is hoped that this review would help researchers to select the suitable characterization methods to analyze the structures and performances of organic electrode materials quickly and effectively.
文摘Polyelectrolyte becomes more and more popular in electrocatalysis.The understanding of electrode/polyelectrolyte interfaces at the molecular level is important for guiding further the polyelectrolyte-based electrocatalysis.Herein,we demonstrate an in-situ surface-enhanced Raman spectroscopic method by using a three-electrode spectroelectrochemical cell towards characterizing the electrode/polyelectrolyte interfaces.The Ag/AgCl and Ag/Ag_(2)O electrodes are used as the reference electrode in the acidic and the alkaline systems,respectively.The working electrode is made of a transparent carbon thin film which loads the electrocatalysts.The applications of this method are demonstrated through the in-situ characterizations of the p-methylthiophenol adsorbed on the Au and Pt and the electrochemical oxidation of Au on polyelectrolyte membranes.The potential-dependent spectral features of these two systems show that this method is a powerful tool for investigating the electrode/polyelectrolyte interfaces in electrocatalysis.
基金The authors gratefully acknowledge financial support from the Ministry of Education and Science,Government of the Republic of Serbia through the Project No.172 060:“New approach to designing materials for energy conversion and storage”.
文摘Electrochemical characteristics of covellite (CuS) are of importance from flotation and metallurgical point of view, as well as due to its potential application in solid state solar cells and in photocatalytic reactions. Also, the compound CuS appears as an intermediary product or a final product in electrochemical oxidation reactions of chalcocite (Cu2S) which exhibits supercapacitor characteristics. Natural copper mineral covellite has been investigated in inorganic sulfate acid electrolytes, as well as in strong alkaline electrolyte. Physical properties of covellite were characterized by X-ray diffraction (XRD) and the active surface was examined by optical and electron microscopy (EM) before and after oxidation in galvanostatic regime. Different electrochemical methods (galvanostatic, potentiostatic, cyclic voltammetry and electrochemical impedance spectroscopy - EIS) have been used. The capacitance of around 21 Fcm-2 (geometric area), serial resistance of about 90 Ωcm2 and leakage resistance of about 1200 Ωcm2 have been measured in 1 M H2SO4. The addition of cupric ions in sulfate electrolyte leads to the significant increasing of the capacitance, but having the increase of self-discharge as a negative side phenomenon. The capacitance of around 6.7 Fcm-2 (geometric area), serial resistance of about 80 Ωcm2 and leakage resistance of about 380 Ωcm2 have been measured in 6 M KOH.
文摘Since the 1980s,single-crystal Pt electrodes with well-defined surface structures have been deemed stable under mild electrochemical conditions(e.g.,in the potential region of electric double layers,underpotential deposition of hydrogen,or mild hydrogen evolution/OH adsorption)and have served as model electrodes for unraveling the structure-performance relation in electrocatalysis.With the advancement of in situ electrochemical microscopy/spectroscopy techniques,subtle surface restructuring under mild electrochemical conditions has been achieved in the last decade.Surface restructuring can considerably modify electrocatalytic properties by generating/destroying highly active sites,thereby interfering with the deduction of the structure-performance relation.In this review,we summarize recent progress in the restructuring of well-defined Pt(-based)electrode surfaces under mild electrochemical conditions.The importance of the meticulous structural characterization of Pt electrodes before,during,and after electrochemical measurements is demonstrated using CO adsorption/oxidation,hydrogen adsorption/evolution,and oxygen reduction as examples.The implications of present findings for correctly identifying the reaction mechanisms and kinetics of other electrocatalytic systems are also briefly discussed.
基金Funded by The National Natural Science Foundation of China(51402185)the Natural Science Foundation of Shanghai(13ZR1454700)
文摘To improve the electrochemical performances of α-MnO2 as electrode materials for supercapacitors, Sn-doped α-MnO2 in the presence of the doping amount of 1%-4% was successfully synthesized by hydrothermal method. As-prepared α-MnO2 presents nanorod shape and no other impurities exist. By ultraviolet-visible absorption spectroscopy, it is convinced that the band gaps of α-MnO2 decrease with increasing Sn-doping amount. Cyclic voltammetry investigation indicates that undoped and doped α-MnO2 all have regular capacitive response. As the scan rate enlarged, the profiles of curves gradually deviate from rectangle. Compared with undoped α-MnO2, doped α-MnO2 has larger specific capacitance. The specific capacitance of 3% doped α-MnO2 reaches 241.0 F/g while undoped α-MnO2 only has 173.0 F/g under 50 m A/g current density in galvanostatical charge-discharge measurement. Enhanced conductivity by Sn-doping is considered to account for doped sample＇s enhanced electrochemical specific capacitance.
基金supported by the Key Research and Development Plan of Shandong Province (2019JZZY020329)the National Key Research and Development Program of China (2017YFB0103904)+1 种基金the National Natural Science Foundation of China (51701211)DongGuan Innovative Research Team Program (2020607134012)。
文摘An investigation into the corrosion characteristics and mechanism of directionally solidified(DSed) Mg-3Zn-xCa(x = 0, 0.2, 0.5,0.8 wt.%) alloys in 0.9 wt.% Na Cl solution is presented. The DSed microstructure consists of columnar dendrites and eutectics distributed in the interdendritic region. The primary dendritic arm spacing(PDAS) and the volume fraction(fv) of the secondary phases are under the significant impact of the content of Ca. The corrosion rates evaluated using electrochemical measurements and immersion tests are accelerated monotonously with the increase of Ca content in DSed alloys. The corrosion resistance of the DSed alloys is significantly affected by the corrosion products film(CPF) and the secondary phases. The corrosion products of DSed Mg-3Zn alloy contain Mg(OH)_(2) and ZnO. The existence of ZnO greatly enhances the corrosion resistance of DSed Mg-3Zn alloy. As for the DSed alloys containing Ca content, a relatively protective CPF without deep pits can form on the surface of DSed Mg-3Zn-0.2Ca specimen during the corrosion. The f_(v)of the secondary phases dominates the corrosion rate of the DSed Mg-Zn-Ca alloys. The corrosion of DSed Mg-3Zn-xCa alloys initiates as a result of microgalvanic coupling between the cathodes of secondary phases and α-Mg matrix anode. Then, the corrosion gradually extends longitudinally with the breakdown of CPF.
文摘A series of electrochemical and long-term corrosion tests were carried out in a neutral saline （5%NaCl） vapor of 35 °C on thermal sprayed WC cermet coatings containing different kinds of metallic binders in order to examine the effect of composition of binder materials on the corrosion behavior. The experimental results revealed that the overall corrosion resistance of WC-Co coating was inferior to that of WC-Co-Cr coating. For the coatings without Cr, WC-Co, general corrosion occurred in binder materials in addition to galvanic corrosion between WC particles and metallic binders in the neutral environment. By contrast, the formation of passive film in the form of surface oxide in the coatings containing Cr, WC-Co-Cr, suppressed the binder and metallic binders to be eroded. It is found that the chemical composition of metallic binder materials is one of the important factors influencing the corrosion resistance of HVOF sprayed WC cermet coatings in the neutral vapor.
文摘The corrosion behavior of Mg-10Gd-xZn(x=2,6 wt.%)alloys in 0.5 wt.%NaCl solution was investigated.Microstructures of both the alloys consisted of(Mg,Zn)_(3) Gd phase and lamellar long period stacking ordered(LPSO)phase.The morphology of the second phase at the grain boundary differed in both alloys:it was a continuous network structure in Mg-10Gd-6Zn,whereas it was relatively discrete in Mg-10Gd-2Zn.The dendrites were finer in size and highly branched in Mg-10Gd-6Zn.The corrosion results indicated that the increase in Zn content increased the corrosion rate in Mg-10Gd-xZn alloys.Micro-galvanic corrosion occurred near the grain boundary in both alloys initially as the grain boundary phase was stable and acted as a cathode,however,filiform corrosion dominated in the later stage,which was facilitated by the LPSO phase in the matrix.Severe micro-galvanic corrosion occurred in Mg-10Gd-6Zn due to the higher volume of second phase.The stability of the second phase at the grain boundary was altered and dissolved after the long immersion times.Probably the NaCl solution chemically reacted with the grain boundary phase and de-stabilized it during the long immersion times,and was removed by the chromic acid used for the corrosion product removal.
文摘The use of magnesium alloys,as a biodegradable medical device,is an interesting challenge for the biomaterials field.Its rapid degradation and the release of hydrogen,when exposed to biological fluids,are the main drawbacks for clinical applications.In this work,a coating made of polydopamine(PDOPA),is used as an intermediate layer to decrease the degradation rate of AZ31 magnesium alloy/polymeric coating system,when exposed to Hank’s solution.Experimental results highlighted:(i)the formation of a thin PDOPA layer,(ii)an increased adhesion in the organic coating/metallic substrate system,(iii)a decrease of two orders of magnitude of the corrosion rate when the PDOPA film is used together with an external organic coating,(iv)the efficacy in the use of PDODA due to the synergistic effect of both,physical and chemical,interactions between the PDOPA layer and the organic coating.
文摘Magnesium alloys are candidates as biodegradable medical materials due to their biocompatibility and favorable mechanical properties.Unfortunately,the high corrosion rate in physiological media and the release of hydrogen,limit their widespread use in biomedical applications.In this work,an intermediate coating based on polydopamine(PDOPA),between Mg substrate and an organic coating,was used to decreasing the degradation rate of AZ31 magnesium alloy,during the long-term exposure in simulated body fluid.Electrochemical Impedance Spectroscopy measurements were carried out to study the corrosion resistance of samples.Results demonstrated that the PDOPA interlayer determined the reduction of the substrate degradation rate.The results were interpreted supposing a synergistic effect which occurred when PDOPA and the organic coating were used together.
基金supported by the National Natural Science Foundation of China(51072170,21321062)the National Basic Research Program of China(2012CB932900)
文摘Dye-sensitized solar cell （DSSC） is one of the most rapidly developed solar cells in the past 20 years. Many characterization methods have been employed for further understanding the operational details of the photo- electric conversion in DSSC as well as the evaluation of cell performance. Electrochemical methods have become pow- erful tools for studying the charge transfer and interfacial process. In this review, we introduce and explain the various electrochemical methods used to characterize and analyze DSSC, including current-voltage （I-V） scan measurement, cyclic voltammetry, electrochemical impedance spec- troscopy, intensity-modulated photocurrent spectroscopy, and intensity-modulated photovoltage spectroscopy. In ad- dition, some applications were provided as samples to elucidate electron transfer kinetics, energy levels and electrocatalytic activity of the materials used in DSSC.
基金Work supported by the National Natural Science Foundation of China.
文摘Electrochemical oxidation of diphenylamine(DPA)in acetonitrile solution produced an adhesive conducting polydiphenylamine(PDPA)film on the electrode,which exhibited multiple colour variation in a wide range of potential.The polymer was characterized by cyclic voltam- merry,FTIR and ESR.The results indicate that the electropolymerization of diphenylamine per- forms via the 4,4＇C—C phenyl-phenyl coupling mechanism.FTIR,ESR and conductivity mea- surements for the different states of PDPA show that polydiphenylamine can be reversibly doped and dedoped either chemically or electrochemically.It is evidenced also that there are paramagnetic species—polarons in PDPA supposed to be the current carrier.
基金Project supported by the National Natural Science Foundation of China (51164007)
文摘The layered material of Ce-doped LiNi1/3Mn1/3Co1/3O2 with α-NaFeO2 was synthesized by a co-precipitation method. X-ray diffraction （XRD） showed that Ce-doped LiNi1/3Mn1/3Co1/3O2 had the same layered structure as the undoped LiNi1/3Mn1/3Co1/3O2. The scanning electron microscopy （SEM） images exhibited that the particle size of Ce-doped LiNi1/3Mn1/3Co1/3O2 was smaller than that of the undoped LiNi1/3Mn1/3Co1/3O2. The Ce-doped LiNi1/3Mn1/3Co1/3O2 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram （CV）, and electrochemical impedance spectra （EIS）. The optimal doping content of Ce was x=0.02 in the LiNi1/3-xMn1/3Co1/3CexO2 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through Ce-doping. The improved electrochemical performances of the Ce-doped LiNi1/3Mn1/3Co1/3O2 cathode materials were attributed to the addition of Ce4＋ ion by stabilizing the layer structure.
基金support from National Natural Science Foundation of China(grant No.52006176,51876175,and 62101438)the Key Research and Development Project of Shaanxi Province(grant No.2022kw-18).
文摘This paper mainly clarified the dispersion mechanism of three typical chemical dispersants which are polyethylene glycol octylphenyl ether(Triton X-100,T-100),polyethylene pyrrolidone(PVP)and carboxymethyl cellulose(CMC)within lithium-ion battery(LIB)slurry.Initially,the optimum amounts of T-100,PVP and CMC are selected from 0%,0.5%,1.5%and 2.5%by evaluating the impedance of LIB slurry in the case of adding each typical chemical dispersant with EIS method.Moreover,the impedance spectrum of three different slurry samples which are PVDF-NMP solution,LiCoO_(2) slurry and Carbon Black(CB)slurry with the optimum amount of each dispersant are also investigated.After using SEM and C element distribution images of LIB slurry to verify the correctness of the dispersion mechanism of each dispersant,it is concluded that the dispersion CMC with its optimum amount 1.5%is the best one to promote the formation of conductive paths and CB-coated LiCoO_(2) network structure within LIB slurry,which has the considerably potential to improve the performance of LIB.
基金financially supported by the National Natural Science Foundation of China(No.51471175)
文摘The effect of residual dissolved oxygen （DO） on the corrosion behavior of carbon steel in 0.1 M NaHCO3 solution was investigated by electrochemical measurements, corrosion mass loss test, scanning electron microscopy （SEM） and X-ray diffraction （XRD）. In the initial immersion stage, the increase of the dissolved oxygen concentration led to the change of from a reductive state of active dissolution to an oxidizing state of pseudo passivation in low carbon steel. While in the final stage, all the steels transformed into the steady state of pseudo passivation. In the anaerobic solution, the formation of c^-FeOOH was attributed to the chemical oxidization of the ferrous corrosion products and the final cathodic process only included the reduction of c^-FeOOH, while in the aerobic solution, it included the reduction of oxygen and （x-FeOOH simultaneously. As the main corrosion products, the content of （x-FeOOH was increased while that of Fe6（OH）12CO3 was decreased with increasing concentration of dissolved oxygen. The total corrosion mass loss of the steel was promoted with the increase of dissolved oxygen concentration.
基金financially supported by the National Natural Science Foundation of China(Nos.51071054 and51271061)the Natural Science Foundation of Guangxi(Nos.2010GXNSFD013004 and 2012GXNSFBA053149)
文摘Low-Co Lal.8Ti0.2MgNi8.9Co0.1 alloys were prepared by magnetic levitation melting followed by annealing treatment. The effect of annealing on the hydrogen storage properties of the alloys was investigated systematically by X-ray diffraction （XRD）, pressure-com- position isotherm （PCI）, and electrochemical measure- ments. The results show that all samples contain LaNi5 and LaMg2Ni9 phases. LaCo5 phase appears at 1,000 ℃. The enthalpy change of all hydrides is close to -30.6 kJ.mo1-1 H2 of LaNi5 compound. Annealing not only increases hydrogen capacity and improves cycling stability but also decreases plateau pressure at 800 and 900 ℃. After annealing, the contraction of cell volume and the increase of hydride stability cause the high rate dischargeability to reduce slightly. The optimum alloy is found to be one annealed at 900 ℃, with its hydrogen capacity reaching up to 1.53 wt%, and discharge capacity remaining 225.1 mAh·g-1 after 140 charge-discharge cycles.
基金Project supported by National Natural Science Foundation of China(51001079,21201129,51374151,51208333)the Top Young Academic Leaders of Higher Learning Institutions of Shanxi,the Doctoral Fund of Ministry of Education of China(20091402110010)+2 种基金the China Postdoctoral Science Foundation(20100471586)the National Natural Science Foundation of Shanxi Province(2011011020-2,2010021023-1)the Postgraduate Innovation Program of Shanxi Province(20113028)
文摘The effect of the rare earth element Er on the microstructures and properties of Mg-Al intermetallic were studied in this experiment. Metallographic and X-ray diffraction（XRD） results showed that the microstructures of Mg-Al-Er alloys varied with Er content. The Mg-44Al-0.5Er and Mg-43.8Al-1.0Er alloys were both composed of Mg17Al12 matrix and Al3 Er phase, whereas Mg-43Al-3.0Er and Mg-42Al-5.0Er were composed of Mg17Al12 matrix, Al3 Er phase, and Mg-Mg17Al12 eutectic. The Mg-42Al-5.0Er alloy showed the highest microhardness, and the values remained nearly stable as Er content increased from 1.0 wt.% to 5.0 wt.%. The dispersed second phase Al3 Er caused the grain refinement of the Mg-Al-Er alloy, which was the main reason for the improvement in microhardness. The corrosion resistance of the Er-containing alloys initially increased and then decreased with increasing Er content. All the Er-containing alloys had the ability to suppress hydrogen evolution, which was the main reason for the higher corrosion resistance of the modified alloys than that of the Mg-44.3Al alloy. Considering the higher hardness and dispersity of the Al3 Er phase, Mg-43.8Al-1.0Er exhibited higher wear resistance than the as-cast Mg-44.3Al alloy.
