The potentiostatic intermittent titration technique(PITT)is widely used to determine the diffusion coefficient of ions in electrode materials for rechargeable batteries such as lithium-ion or sodium-ion batteries,pred...The potentiostatic intermittent titration technique(PITT)is widely used to determine the diffusion coefficient of ions in electrode materials for rechargeable batteries such as lithium-ion or sodium-ion batteries,predicated on the assumption that the insertion/extraction of ions in the host materials is governed by diffusion.However,in practical scenarios,the electrochemical process might be dominated by interfacial reaction kinetics rather than diffusion.The present work derives analytical equations for electric current by considering the finite interfacial reaction kinetics and small overpotentials during PITT measurements and further studies the chemical stress field induced by the interfacial reaction-controlled ion insertion.The exchange current density(j_(0))can be ascertained using the analytical equation,which dictates the magnitude and decay rate of the electric current during a PITT process.The electric current decays more rapidly,and consequently,the lithium concentration reaches equilibrium faster for larger values of j_(0).The magnitude of the chemical stress is independent of j_(0) but depends on the overpotential.展开更多
This study aims to characterize the cavitation damage behavior of aluminum alloys in seawater and thus to enhance its cavitation resistance. Potentiostatic experiments were performed under various potential conditions...This study aims to characterize the cavitation damage behavior of aluminum alloys in seawater and thus to enhance its cavitation resistance. Potentiostatic experiments were performed under various potential conditions to determine the optimum protection potentials, at which cavitation damage was suppressed. A potential range was selected for the experiment from -2.2 to -1.4 V, which corresponded to the concentration and activation polarization regions on the cathodic polarization curve of the 5083-H116 alloy. After the experiments, the current density-time behavior was investigated, and the degree of surface damage was observed using three-dimensional microscopy and scanning electron microscopy （SEM）, The optimum protection potential was determined to be in the range of-l.9 to -1.5 V under which the cavitation damage was reduced significantly.展开更多
Designing transition metal nickel-cobalt-based battery-type electrode materials driven by anions is crucial for achieving rapid OH-ion transport under electrochemical activation conditions,thereby improving capacitanc...Designing transition metal nickel-cobalt-based battery-type electrode materials driven by anions is crucial for achieving rapid OH-ion transport under electrochemical activation conditions,thereby improving capacitance performance.Herein,borate anions are selected through theoretical calculations,and twodimensional(2D)defect-rich amorphous nickel-cobalt-based borate is synthesized via a facile chemical reduction method.Under potentiostatic modification,activated products(NCB-G-E)are obtained.In situ Raman spectra reveal that electron-deficient borate extracts electrons from metal centers,facilitating the oxidation state transition of Ni and Co.Theoretical calculations show that in situ adsorbed borate regulates the d-band centers of metal sites,enhancing OH^(-)intermediate adsorption.Meanwhile,borate anion adsorption accelerates the deprotonation and activation processes.Electrochemical tests demonstrate that NCB-G-E displays superior capacitance performance,with a high quality specific capacity of383.3 mA h g^(-1)and 65% retention rate at 30 A g^(-1),surpassing most nickel-cobalt-based electrodes.The assembled asymmetric supercapacitor presents an impressive energy density of 68.2 Wh kg^(-1)and good cycling stability.This work highlights the role of electron-deficient borate in tuning metal band structure and promoting oxidation state transition through synergistic defect advantages,offering new prospects for advanced battery-type energy storage materials.展开更多
In deaerated 0.05 M,0.1 M,0.2 M and 0.5 M K_(2)HPO_(4) solutions with pH 9.5,AZ31 magnesium(Mg)alloy was subjected to potentiostatic polarization at−0.8 VSCE to deposit a phosphate conversion coating.The morphology,st...In deaerated 0.05 M,0.1 M,0.2 M and 0.5 M K_(2)HPO_(4) solutions with pH 9.5,AZ31 magnesium(Mg)alloy was subjected to potentiostatic polarization at−0.8 VSCE to deposit a phosphate conversion coating.The morphology,structure,chemical composition,and protective performance of the conversion coating during the formation process were characterized.The results showed that amorphous Mg(OH)_(2) and MgHPO_(4) and crystallized KMgPO_(4)·6H2O(struvite-K)were successively deposited on the surface of AZ31 Mg alloy in the four solutions.MgHPO_(4) was converted from Mg(OH)_(2),while struvite-K was transformed from MgHPO_(4).The distribution of Mg(OH)_(2),MgHPO_(4) and struvite-K along the thickness of the coating difers with K_(2)HPO_(4) concentration.As the concentration of K_(2)HPO_(4) increased,the coating time was gradually shortened,and the coating was gradually thinned.Meanwhile,the ratio of the nucleation rate to the growth rate of struvite-K crystal nuclei increased,resulting in a decrease in the size of struvite-K crystal.When the concentration of K_(2)HPO_(4) increased from 0.05 to 0.1 M,the content of struvite-K increased,and the protective performance of the coating was enhanced.However,as the concentration of K_(2)HPO_(4) continued to increase to 0.5 M,the content of struvite-K and the protective performance of the coating decreased.展开更多
The coordination polymer poly（nickel-ethylenetetrathiolate） （poly（Ni-ett））, formed by nickel（Ⅱ） and 1,1,2,2-ethenetetrathiolate （ett）, is the most promising N-type organic thermoelectric material ever repor...The coordination polymer poly（nickel-ethylenetetrathiolate） （poly（Ni-ett））, formed by nickel（Ⅱ） and 1,1,2,2-ethenetetrathiolate （ett）, is the most promising N-type organic thermoelectric material ever reported; it is synthesized via potentiostatic deposition, and the effect of different applied potentials on the optimal performance of the polymers is investigated. The optimal thermoelectric property ofpoly（Ni-ett） synthesized at 0.6 V is remarkably greater than that of the polymers synthesized at 1 and 1.6 V, exhibiting a maximum power factor of up to 131.6μW/mK2 at 360 K. Furthermore, the structure-property correlation ofpoly（Ni-ett） is also extensively investigated. X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS） analyses revealed that the larger size of crystalline domains and the higher oxidation state of poly（Ni-ett） synthesized at 0.6 V possibly results in the higher bulk mobility and carrier concentration in the polymer chains, respectively, accounting for the enhanced power factor.展开更多
The high-temperature requirement for liquid iron smelting via molten oxide electrolysis presents significant challenges.This study investigates the electrochemical reduction of Fe(Ⅲ)in a novel low-temperature electro...The high-temperature requirement for liquid iron smelting via molten oxide electrolysis presents significant challenges.This study investigates the electrochemical reduction of Fe(Ⅲ)in a novel low-temperature electrolyte,Na_(2)SiO_(3)-SiO_(2)-Fe_(2)O_(3),utilizing cyclic voltammetry and square wave voltammetry techniques.The results show that Fe(Ⅲ)reduction occurs in two steps:Fe(Ⅲ)+e^(−)→Fe(Ⅱ),Fe(Ⅱ)+2e^(−)→Fe,and that the redox process of Fe(Ⅲ)/Fe(Ⅱ)at the tungsten electrode is an irreversible reaction controlled by diffusion.The diffusion coefficients of Fe(Ⅲ)in the molten Na_(2)SiO_(3)-SiO_(2)-Fe_(2)O_(3)in the temperature range of 1248–1278 K are between 1.86×10^(−6)cm^(2)/s and 1.58×10^(−4)cm^(2)/s.The diffusion activation energy of Fe(Ⅲ)in the molten salt is 1825.41 kJ/mol.As confirmed by XRD analysis,potentiostatic electrolysis at−0.857 V(vs.O_(2)/O_(complex)^(2-))for 6 h produces metallic iron on the cathode.展开更多
We measured the anodic hydrogen evolution rates for various applied anodic current densities and estimated the corresponding cathodic hydrogen evolution rates.The estimated cathodic hydrogen evolution rates were less ...We measured the anodic hydrogen evolution rates for various applied anodic current densities and estimated the corresponding cathodic hydrogen evolution rates.The estimated cathodic hydrogen evolution rates were less than the measured anodic hydrogen evolution rates,contradicting the enhanced catalytic activity mechanism of Mg corrosion.In addition,this model was contradicted by the measured apparent Mg valence of 1.2±0.1.In contrast,the uni-positive Mg^(+)mechanism of Mg corrosion was supported by(i)the apparent Mg valence of 1.2±0.1,and(ii)the fact that the measured anodic hydrogen evolution rate increased with increasing weight loss rate.展开更多
The work concerned the electrochemical behaviors of Y（Ⅲ） on W and Ni electrodes in molten LiCl-KCl salts by a series of electrochemical techniques. The electrochemical reaction of Y（Ⅲ） to Y（0） proceeded in a o...The work concerned the electrochemical behaviors of Y（Ⅲ） on W and Ni electrodes in molten LiCl-KCl salts by a series of electrochemical techniques. The electrochemical reaction of Y（Ⅲ） to Y（0） proceeded in a one-step reduction process with the exchange of three electrons, Y（Ⅲ）＋3e^–→Y（0）. Compared with the cyclic voltammogram and square wave voltammogram obtained on W electrode, the reduction potential of Y（Ⅲ） on Ni electrode was observed at less negative potential than the one of Y（Ⅲ） to give pure Y metal on W electrode, which revealed the occurrence of underpotential deposition of Y（Ⅲ） on Ni electrode. Electromotive force（emf） measurements were performed to calculate the relative partial molar Gibbs energies and activities of Y in Y-Ni alloys. The standard Gibbs energies of formation for different Y-Ni intermetallic compounds were also estimated. The different Y-Ni alloys were formed by potentiostatic electrolysis at different potentials and characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, and energy dispersive spectrometry（EDS）. It was found that four intermetallic compounds, YNi5, Y2Ni7, YNi3 and YNi2, were selectively produced by controlling applied potential.展开更多
The electrodeposition of nickel-silicon carbide coatings on a copper electrode was done by mixing SiC particles in the nickel electrodeposition solution.The influence of surfactants and silicon carbide particle size o...The electrodeposition of nickel-silicon carbide coatings on a copper electrode was done by mixing SiC particles in the nickel electrodeposition solution.The influence of surfactants and silicon carbide particle size on uniformity and quantity of silicon carbide particles in nickel-silicon carbide composite coatings was investigated.It was found that particle size affects the nucleation overpotential,with 40 nm silicon carbide nanoparticles more effective in promoting nickel nucleation than 500 nm particles due to an increase in active nucleation sites.In terms of surfactants,anionic surfactant sodium dodecyl sulfate(SDS)produced better dispersion of 40 nm silicon carbide particles than cationic surfactant cetyltrimethyl ammonium bromide(CTAB),but little difference was found between the two when 500 nm silicon carbide particles were used.Thus,although the suspension of silicon carbide particles can be improved and their co-deposition can be promoted with a cationic surfactant CTAB,it is less effective than an anionic surfactant SDS in terms of surface finish.展开更多
AZ31 magnesium（Mg） alloy was potentiostatic polarized in 0.1 M deaerated KF solution with pH 7.5 from-0.4 V to-1.4 V with an interval of-0.2 V. The polarization process was described by the potentiostatic current de...AZ31 magnesium（Mg） alloy was potentiostatic polarized in 0.1 M deaerated KF solution with pH 7.5 from-0.4 V to-1.4 V with an interval of-0.2 V. The polarization process was described by the potentiostatic current decay. The resultant film was analyzed by scanning electron microscopy（SEM）, X-ray diffraction（XRD）, X-ray photoelectron spectroscopy（XPS） and electrochemical impedance spectroscopy（EIS）. The results demonstrated that the deposited film included a Mg（OH）2/MgF2 containing inner layer and a Mg（OH）-2/MgF2/KMgF3 comprising outer layer. The high polarized potential produced high content of MgF2 but low content of KMgF3 and thin film. Conversely, the low polarized potential produced small content of MgF2 but high content of KMgF3 and thick film. The optimal corrosion resistance of the deposited film was obtained at-1.4 V, which was closely related with the content of MgF2 and KMgF3 and the film thickness.展开更多
Methods for evaluating the resistance to cathodic disbondment （RCD） of anti-corrosion coatings on buried pipelines were reviewed. It is obvious that these traditional cathodic disbondment tests （CDT） have some dis...Methods for evaluating the resistance to cathodic disbondment （RCD） of anti-corrosion coatings on buried pipelines were reviewed. It is obvious that these traditional cathodic disbondment tests （CDT） have some disadvantages and the evaluated results are only simple figures and always rely on the subjective experience of the operator. A new electrochemical method for evaluating the RCD of coatings, that is, the potentiostatic evaluation method （PEM）, was developed and studied. During potentiostatic anodic polarization testing, the changes of stable polarization current of specimens before and after cathodic disbonding （CD） were measured, and the degree of cathodic disbondment of the coating was quantitatively evaluated, among which the equivalent cathodic disbonded distance AD was suggested as a parameter for evaluating the RCD. A series of testing parameters of the PEM were determined in these experiments.展开更多
Pitting initiation and stable propagation behaviors of 2205 duplex stainless steel were investigated in the hot concentrated seawater under vacuum pressures by potentiostatic polarization. Both applied potentials and ...Pitting initiation and stable propagation behaviors of 2205 duplex stainless steel were investigated in the hot concentrated seawater under vacuum pressures by potentiostatic polarization. Both applied potentials and vacuum pressures greatly influence the pitting corrosion. Higher potentials lead to much faster stable pitting initiation and growth rates in both static(101.3 kPa) and dynamic(28.4 kPa) solutions. The pressure reduction can also accelerate the pitting initiation rate. However, the boiling of solution can influence the pitting propagation mechanism. The dynamic actions of boiling bubbles are unfavorable to the pit propagation and result in the formation of relatively smooth pit bottom without secondary pits.展开更多
316L SS alloy was tested under different applied potentials to study the susceptibility of this alloy to crevice corrosion. XPS measurements have been carried out to detect and define the products which formed on the ...316L SS alloy was tested under different applied potentials to study the susceptibility of this alloy to crevice corrosion. XPS measurements have been carried out to detect and define the products which formed on the surface of 316L SS in 3.5% NaCl at room temperature at applied potential = 200 mVSCE. The formation of Fe, Cr and Mo compounds were found, and these compounds play a great role in protecting the alloy which was found. The boundaries of the corroded area under washer teeth are in agreement with IR drop. The potentiodynamic technique is also studied to examine the overall corrosion behavior of 316L SS.展开更多
Under the condition of weak acidity of pH 5.2, a sensitive vitamin B2 electrochemical sensor based on molecularly imprinted nonconducting polymer of o-aminophenol by potentiostatic polymerization in the presence of te...Under the condition of weak acidity of pH 5.2, a sensitive vitamin B2 electrochemical sensor based on molecularly imprinted nonconducting polymer of o-aminophenol by potentiostatic polymerization in the presence of template(vitamin B2) on a glassy carbon electrode was prepared, and its performance was studied. The sensor exhibited good sensitivity and selectivity to VB2. The detection limit went down to 2.3851nM, and a linear relationship between the current incremental and the concentration was found in the range of 10~120nM. And the sensor could use in detection of VB2 real sample for a long time and show good reproducibility. The average recovery rate to VB2 was 98.41%.展开更多
Co deposition of Ho with Co was studied in dimethylsulfoxide (DMSO) by cyclic voltammetry and potentiostatic deposition at room temperature. The cyclic voltammogram shows that the codeposition of Ho with Co can be at...Co deposition of Ho with Co was studied in dimethylsulfoxide (DMSO) by cyclic voltammetry and potentiostatic deposition at room temperature. The cyclic voltammogram shows that the codeposition of Ho with Co can be attributed to induced codeposition mechanism, for the codeposition potential is more negative than the deposition potential of Co but positive than that of Ho. For the potentiostatic deposition used in Ho Co alloys preparation, the results indicate that in the range of selected concentration the potential is the main factor determining the content of Ho in Ho Co alloys, while the composition of Ho 3+ and Co 2+ in electrolyte solution has less influence. According to the analysis of X ray diffraction, EDAX, and scanning electron microscopy, uniform, compact and amorphous films on Cu can be obtained at -1 8 V (vs.SCE) in 0 165 mol·L -1 Ho(NO 3) -0 135 mol·L -1 CoCl 2 DMSO solution.展开更多
The cathodic reduction mechanism of Hf(Ⅳ)ions in a fused Na Cl–KCl–Na F–K_(2) HfF_(6) salt system was studied in various Na F concentrations at 1073 K to obtain a purified dendritic Hf metal.The results of cyclic ...The cathodic reduction mechanism of Hf(Ⅳ)ions in a fused Na Cl–KCl–Na F–K_(2) HfF_(6) salt system was studied in various Na F concentrations at 1073 K to obtain a purified dendritic Hf metal.The results of cyclic voltammetry and square wave voltammetry indicated that the reduction process comprised two steps of Hf(Ⅳ)→Hf(Ⅱ)and Hf(Ⅱ)→Hf at low Na F concentrations(0<molar ratio of[F-/Hf 4+]≤17.39)and one step of Hf(Ⅳ)→Hf at high Na F concentrations(17.39<molar ratio of[F-/Hf 4+]<23.27).The structure and morphology of the deposits obtained in potentiostatic electrolysis in the one-step reduction process were analyzed and verified by X-ray diffraction,scanning electron microscopy,and energy dispersive X-ray spectrometry.In the one-step reduction process,the disproportionation reaction between the Hf metal and Hf complex ions was inhibited,and a large dendrite Hf metal was achieved in molten salt electrorefining.展开更多
In deaerated 0.1 M KF solution at pH 5, pH 7.5 and pH 9, fluoride films were deposited on AZ31 magnesium (Mg) alloy at − 1.4 V vs saturated calomel electrode (SCE). The morphology, phase composition, elemental and com...In deaerated 0.1 M KF solution at pH 5, pH 7.5 and pH 9, fluoride films were deposited on AZ31 magnesium (Mg) alloy at − 1.4 V vs saturated calomel electrode (SCE). The morphology, phase composition, elemental and compositional depth distribution of different fluoride films and their influences on the corrosion resistance of AZ31 Mg alloy were explored in detail. The results indicated that the films deposited at weak acidic and nearly neutral pH consisted of two layers with amorphous Mg(OH)_(2) and MgF_(2) as the inner layer, and Mg(OH)_(2), MgF_(2) and KMgF_(3) crystals the outer layer. The film deposited at alkaline pH was a monolayer structure consisting of amorphous Mg(OH)_(2) as the major constitute and MgF_(2) as the minor constitute. The protectiveness of fluoride film was intimately related to its composition and structure. The content and crystal regularity of KMgF_(3) were the two main factors influencing the protectiveness of fluoride film. The fluoride film deposited at pH 7.5 offered the best protection to AZ31 Mg alloy.展开更多
A novel electrochemical method for the rapid detection of organophosphorus pesticide residues was realized on a dual-channel screen-printed electrode （DSPE） that was integrated with a portable smartphone-controlled ...A novel electrochemical method for the rapid detection of organophosphorus pesticide residues was realized on a dual-channel screen-printed electrode （DSPE） that was integrated with a portable smartphone-controlled potentiostat. The two carbon working channels of DSPE were first modified by electrodepositing of Prussian blue. The channels were then modified with acetylcholinesterase （ACHE） via Nation. The inhibition ratio of AChE was detected by comparing the electrical current of acetylthiocholine （ATCh） that was catalyzed by the enzyme electrodes with （channel 1） and without （channel 2） organophosphorus pesticide. Inhibition ratios were related with the negative logarithm of the organophosphorus pesticide （trichlorfon, oxamyl, and isocarbophos） concentrations at optimum experimental conditions （pH 6.9 of electrolyte, 0.2V working potential, 2.5μL AChE modification amount, and 15 min inhibition time）. The linear equations were 1%=32.301gC＋ 253.3 （R=0.9750） for isocarbophos, I% = 35.991gC＋ 270.1 （R = 0.9668） for chlorpyrifos, and 1% = 33.701gC＋ 250.5 （R = 0.9606） for trichlorfon. The detection limits were calculated as 10-7 g/mL. Given that the inhibition ratios were only related with pesticide concentration and not with pesticide species, the proposed electrodes and electrometer can rapidly detect universal organophosphorus pesticides and assess pesticide pollution.展开更多
A circuit model of the Amperometric immunosensor for use in the biosensor system-on-chip simulation is proposed in this paper.The model parameters are extracted with several methods and verified by MATLAB and SPICE si...A circuit model of the Amperometric immunosensor for use in the biosensor system-on-chip simulation is proposed in this paper.The model parameters are extracted with several methods and verified by MATLAB and SPICE simulation.A CMOS potentiostat circuit required for conditioning the Amperometric immunosensor is also included in the circuit model.The mean square error norm of the simulated curve against the measured one is 8.65×10^(-17) The whole circuit has been fabricated in a 0.35μm CMOS process.展开更多
This paper studies the effect of expansion ratio on the corrosion rate of the expanded tubes exposed to sea water as well as the microstructure changes caused by the expansion of Cr-Mo steel tubes to large permanent d...This paper studies the effect of expansion ratio on the corrosion rate of the expanded tubes exposed to sea water as well as the microstructure changes caused by the expansion of Cr-Mo steel tubes to large permanent deformations. 2.25 Cr-1.0 Mo steel (schedule 40 and schedule 80) tubes were subjected to various expansion ratios of 10%, 15%, 20%, and 25% by pushing conical mandrels through them using a piston. The microstructure was also studied to determine the effect of the expansion on the grain structure of the material. Microscopic examination of the expanded tubes revealed that grains elongate along the direction of the hoop stress and this elongation increases with an increase of expansion ratio. Moreover, it was found that corrosion rate and hardness increase with an increase in expansion ratio.展开更多
基金supported by the National Natural Science Foundation of China(No.12374003)the Guangdong Basic and Applied Basic Research Foundation(No.2024A1515030256)the Shenzhen Science and Technology Program(Grant Nos.JCYJ20220531095208019 and GXWD20231129103124001).
文摘The potentiostatic intermittent titration technique(PITT)is widely used to determine the diffusion coefficient of ions in electrode materials for rechargeable batteries such as lithium-ion or sodium-ion batteries,predicated on the assumption that the insertion/extraction of ions in the host materials is governed by diffusion.However,in practical scenarios,the electrochemical process might be dominated by interfacial reaction kinetics rather than diffusion.The present work derives analytical equations for electric current by considering the finite interfacial reaction kinetics and small overpotentials during PITT measurements and further studies the chemical stress field induced by the interfacial reaction-controlled ion insertion.The exchange current density(j_(0))can be ascertained using the analytical equation,which dictates the magnitude and decay rate of the electric current during a PITT process.The electric current decays more rapidly,and consequently,the lithium concentration reaches equilibrium faster for larger values of j_(0).The magnitude of the chemical stress is independent of j_(0) but depends on the overpotential.
基金sponsored by the Cooperative Promotion Center of Science&Technology of Jeonnam Technopark and Ministry of Education,Science and Technology (MEST) through"The research&development support of Jeonnam southwest science park"
文摘This study aims to characterize the cavitation damage behavior of aluminum alloys in seawater and thus to enhance its cavitation resistance. Potentiostatic experiments were performed under various potential conditions to determine the optimum protection potentials, at which cavitation damage was suppressed. A potential range was selected for the experiment from -2.2 to -1.4 V, which corresponded to the concentration and activation polarization regions on the cathodic polarization curve of the 5083-H116 alloy. After the experiments, the current density-time behavior was investigated, and the degree of surface damage was observed using three-dimensional microscopy and scanning electron microscopy （SEM）, The optimum protection potential was determined to be in the range of-l.9 to -1.5 V under which the cavitation damage was reduced significantly.
基金supported by the National Natural Science Foundation of China(22478422,22238012,and 22178384)Science Foundation of China University of Petroleum,Beijing(2462024QNXZ003)CHN Energy Investment Group(GJNY23-23)。
文摘Designing transition metal nickel-cobalt-based battery-type electrode materials driven by anions is crucial for achieving rapid OH-ion transport under electrochemical activation conditions,thereby improving capacitance performance.Herein,borate anions are selected through theoretical calculations,and twodimensional(2D)defect-rich amorphous nickel-cobalt-based borate is synthesized via a facile chemical reduction method.Under potentiostatic modification,activated products(NCB-G-E)are obtained.In situ Raman spectra reveal that electron-deficient borate extracts electrons from metal centers,facilitating the oxidation state transition of Ni and Co.Theoretical calculations show that in situ adsorbed borate regulates the d-band centers of metal sites,enhancing OH^(-)intermediate adsorption.Meanwhile,borate anion adsorption accelerates the deprotonation and activation processes.Electrochemical tests demonstrate that NCB-G-E displays superior capacitance performance,with a high quality specific capacity of383.3 mA h g^(-1)and 65% retention rate at 30 A g^(-1),surpassing most nickel-cobalt-based electrodes.The assembled asymmetric supercapacitor presents an impressive energy density of 68.2 Wh kg^(-1)and good cycling stability.This work highlights the role of electron-deficient borate in tuning metal band structure and promoting oxidation state transition through synergistic defect advantages,offering new prospects for advanced battery-type energy storage materials.
基金financially supported by the National Natural Science Foundation of China(No.52373322).
文摘In deaerated 0.05 M,0.1 M,0.2 M and 0.5 M K_(2)HPO_(4) solutions with pH 9.5,AZ31 magnesium(Mg)alloy was subjected to potentiostatic polarization at−0.8 VSCE to deposit a phosphate conversion coating.The morphology,structure,chemical composition,and protective performance of the conversion coating during the formation process were characterized.The results showed that amorphous Mg(OH)_(2) and MgHPO_(4) and crystallized KMgPO_(4)·6H2O(struvite-K)were successively deposited on the surface of AZ31 Mg alloy in the four solutions.MgHPO_(4) was converted from Mg(OH)_(2),while struvite-K was transformed from MgHPO_(4).The distribution of Mg(OH)_(2),MgHPO_(4) and struvite-K along the thickness of the coating difers with K_(2)HPO_(4) concentration.As the concentration of K_(2)HPO_(4) increased,the coating time was gradually shortened,and the coating was gradually thinned.Meanwhile,the ratio of the nucleation rate to the growth rate of struvite-K crystal nuclei increased,resulting in a decrease in the size of struvite-K crystal.When the concentration of K_(2)HPO_(4) increased from 0.05 to 0.1 M,the content of struvite-K increased,and the protective performance of the coating was enhanced.However,as the concentration of K_(2)HPO_(4) continued to increase to 0.5 M,the content of struvite-K and the protective performance of the coating decreased.
基金supported by the National Basic Research Program of China (2013CB632506)the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB12000000)+1 种基金Key Project of National Natural Science Foundation of China (51336009)National Natural Science Foundation of China (21290191, 21333011)
文摘The coordination polymer poly（nickel-ethylenetetrathiolate） （poly（Ni-ett））, formed by nickel（Ⅱ） and 1,1,2,2-ethenetetrathiolate （ett）, is the most promising N-type organic thermoelectric material ever reported; it is synthesized via potentiostatic deposition, and the effect of different applied potentials on the optimal performance of the polymers is investigated. The optimal thermoelectric property ofpoly（Ni-ett） synthesized at 0.6 V is remarkably greater than that of the polymers synthesized at 1 and 1.6 V, exhibiting a maximum power factor of up to 131.6μW/mK2 at 360 K. Furthermore, the structure-property correlation ofpoly（Ni-ett） is also extensively investigated. X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS） analyses revealed that the larger size of crystalline domains and the higher oxidation state of poly（Ni-ett） synthesized at 0.6 V possibly results in the higher bulk mobility and carrier concentration in the polymer chains, respectively, accounting for the enhanced power factor.
基金Project(52074084)supported by the National Natural Science Foundation of China。
文摘The high-temperature requirement for liquid iron smelting via molten oxide electrolysis presents significant challenges.This study investigates the electrochemical reduction of Fe(Ⅲ)in a novel low-temperature electrolyte,Na_(2)SiO_(3)-SiO_(2)-Fe_(2)O_(3),utilizing cyclic voltammetry and square wave voltammetry techniques.The results show that Fe(Ⅲ)reduction occurs in two steps:Fe(Ⅲ)+e^(−)→Fe(Ⅱ),Fe(Ⅱ)+2e^(−)→Fe,and that the redox process of Fe(Ⅲ)/Fe(Ⅱ)at the tungsten electrode is an irreversible reaction controlled by diffusion.The diffusion coefficients of Fe(Ⅲ)in the molten Na_(2)SiO_(3)-SiO_(2)-Fe_(2)O_(3)in the temperature range of 1248–1278 K are between 1.86×10^(−6)cm^(2)/s and 1.58×10^(−4)cm^(2)/s.The diffusion activation energy of Fe(Ⅲ)in the molten salt is 1825.41 kJ/mol.As confirmed by XRD analysis,potentiostatic electrolysis at−0.857 V(vs.O_(2)/O_(complex)^(2-))for 6 h produces metallic iron on the cathode.
基金the financial support for this research by the Australian Research Council(ARC)through the discovery grant DP170102557
文摘We measured the anodic hydrogen evolution rates for various applied anodic current densities and estimated the corresponding cathodic hydrogen evolution rates.The estimated cathodic hydrogen evolution rates were less than the measured anodic hydrogen evolution rates,contradicting the enhanced catalytic activity mechanism of Mg corrosion.In addition,this model was contradicted by the measured apparent Mg valence of 1.2±0.1.In contrast,the uni-positive Mg^(+)mechanism of Mg corrosion was supported by(i)the apparent Mg valence of 1.2±0.1,and(ii)the fact that the measured anodic hydrogen evolution rate increased with increasing weight loss rate.
基金Project supported by the National Natural Science Foundation of China(21271054,11575047,21173060,11675044),the Major Research Plan of the National Natural Science Foundation of China(91326113,91226201)the Fundamental Research Funds for the Central Universities(HEUCF2016012)
文摘The work concerned the electrochemical behaviors of Y（Ⅲ） on W and Ni electrodes in molten LiCl-KCl salts by a series of electrochemical techniques. The electrochemical reaction of Y（Ⅲ） to Y（0） proceeded in a one-step reduction process with the exchange of three electrons, Y（Ⅲ）＋3e^–→Y（0）. Compared with the cyclic voltammogram and square wave voltammogram obtained on W electrode, the reduction potential of Y（Ⅲ） on Ni electrode was observed at less negative potential than the one of Y（Ⅲ） to give pure Y metal on W electrode, which revealed the occurrence of underpotential deposition of Y（Ⅲ） on Ni electrode. Electromotive force（emf） measurements were performed to calculate the relative partial molar Gibbs energies and activities of Y in Y-Ni alloys. The standard Gibbs energies of formation for different Y-Ni intermetallic compounds were also estimated. The different Y-Ni alloys were formed by potentiostatic electrolysis at different potentials and characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, and energy dispersive spectrometry（EDS）. It was found that four intermetallic compounds, YNi5, Y2Ni7, YNi3 and YNi2, were selectively produced by controlling applied potential.
基金Project(20180550242)supported by the Liaoning Science and Technology Plan,China。
文摘The electrodeposition of nickel-silicon carbide coatings on a copper electrode was done by mixing SiC particles in the nickel electrodeposition solution.The influence of surfactants and silicon carbide particle size on uniformity and quantity of silicon carbide particles in nickel-silicon carbide composite coatings was investigated.It was found that particle size affects the nucleation overpotential,with 40 nm silicon carbide nanoparticles more effective in promoting nickel nucleation than 500 nm particles due to an increase in active nucleation sites.In terms of surfactants,anionic surfactant sodium dodecyl sulfate(SDS)produced better dispersion of 40 nm silicon carbide particles than cationic surfactant cetyltrimethyl ammonium bromide(CTAB),but little difference was found between the two when 500 nm silicon carbide particles were used.Thus,although the suspension of silicon carbide particles can be improved and their co-deposition can be promoted with a cationic surfactant CTAB,it is less effective than an anionic surfactant SDS in terms of surface finish.
基金supported financially by the National Natural Science Foundation of China (No. 51701221)
文摘AZ31 magnesium（Mg） alloy was potentiostatic polarized in 0.1 M deaerated KF solution with pH 7.5 from-0.4 V to-1.4 V with an interval of-0.2 V. The polarization process was described by the potentiostatic current decay. The resultant film was analyzed by scanning electron microscopy（SEM）, X-ray diffraction（XRD）, X-ray photoelectron spectroscopy（XPS） and electrochemical impedance spectroscopy（EIS）. The results demonstrated that the deposited film included a Mg（OH）2/MgF2 containing inner layer and a Mg（OH）-2/MgF2/KMgF3 comprising outer layer. The high polarized potential produced high content of MgF2 but low content of KMgF3 and thin film. Conversely, the low polarized potential produced small content of MgF2 but high content of KMgF3 and thick film. The optimal corrosion resistance of the deposited film was obtained at-1.4 V, which was closely related with the content of MgF2 and KMgF3 and the film thickness.
基金This work is financially supported by the National Natural Science Foundation of China (No.2992021).
文摘Methods for evaluating the resistance to cathodic disbondment （RCD） of anti-corrosion coatings on buried pipelines were reviewed. It is obvious that these traditional cathodic disbondment tests （CDT） have some disadvantages and the evaluated results are only simple figures and always rely on the subjective experience of the operator. A new electrochemical method for evaluating the RCD of coatings, that is, the potentiostatic evaluation method （PEM）, was developed and studied. During potentiostatic anodic polarization testing, the changes of stable polarization current of specimens before and after cathodic disbonding （CD） were measured, and the degree of cathodic disbondment of the coating was quantitatively evaluated, among which the equivalent cathodic disbonded distance AD was suggested as a parameter for evaluating the RCD. A series of testing parameters of the PEM were determined in these experiments.
基金supported by the National Natural Science Foundation of China(Grant Nos.U1960103 and 51571139)。
文摘Pitting initiation and stable propagation behaviors of 2205 duplex stainless steel were investigated in the hot concentrated seawater under vacuum pressures by potentiostatic polarization. Both applied potentials and vacuum pressures greatly influence the pitting corrosion. Higher potentials lead to much faster stable pitting initiation and growth rates in both static(101.3 kPa) and dynamic(28.4 kPa) solutions. The pressure reduction can also accelerate the pitting initiation rate. However, the boiling of solution can influence the pitting propagation mechanism. The dynamic actions of boiling bubbles are unfavorable to the pit propagation and result in the formation of relatively smooth pit bottom without secondary pits.
文摘316L SS alloy was tested under different applied potentials to study the susceptibility of this alloy to crevice corrosion. XPS measurements have been carried out to detect and define the products which formed on the surface of 316L SS in 3.5% NaCl at room temperature at applied potential = 200 mVSCE. The formation of Fe, Cr and Mo compounds were found, and these compounds play a great role in protecting the alloy which was found. The boundaries of the corroded area under washer teeth are in agreement with IR drop. The potentiodynamic technique is also studied to examine the overall corrosion behavior of 316L SS.
文摘Under the condition of weak acidity of pH 5.2, a sensitive vitamin B2 electrochemical sensor based on molecularly imprinted nonconducting polymer of o-aminophenol by potentiostatic polymerization in the presence of template(vitamin B2) on a glassy carbon electrode was prepared, and its performance was studied. The sensor exhibited good sensitivity and selectivity to VB2. The detection limit went down to 2.3851nM, and a linear relationship between the current incremental and the concentration was found in the range of 10~120nM. And the sensor could use in detection of VB2 real sample for a long time and show good reproducibility. The average recovery rate to VB2 was 98.41%.
基金Project supported by Natural Science Foundation of Guangdong Province (011215)
文摘Co deposition of Ho with Co was studied in dimethylsulfoxide (DMSO) by cyclic voltammetry and potentiostatic deposition at room temperature. The cyclic voltammogram shows that the codeposition of Ho with Co can be attributed to induced codeposition mechanism, for the codeposition potential is more negative than the deposition potential of Co but positive than that of Ho. For the potentiostatic deposition used in Ho Co alloys preparation, the results indicate that in the range of selected concentration the potential is the main factor determining the content of Ho in Ho Co alloys, while the composition of Ho 3+ and Co 2+ in electrolyte solution has less influence. According to the analysis of X ray diffraction, EDAX, and scanning electron microscopy, uniform, compact and amorphous films on Cu can be obtained at -1 8 V (vs.SCE) in 0 165 mol·L -1 Ho(NO 3) -0 135 mol·L -1 CoCl 2 DMSO solution.
基金the National Natural Science Foundation of China(No.51204021)。
文摘The cathodic reduction mechanism of Hf(Ⅳ)ions in a fused Na Cl–KCl–Na F–K_(2) HfF_(6) salt system was studied in various Na F concentrations at 1073 K to obtain a purified dendritic Hf metal.The results of cyclic voltammetry and square wave voltammetry indicated that the reduction process comprised two steps of Hf(Ⅳ)→Hf(Ⅱ)and Hf(Ⅱ)→Hf at low Na F concentrations(0<molar ratio of[F-/Hf 4+]≤17.39)and one step of Hf(Ⅳ)→Hf at high Na F concentrations(17.39<molar ratio of[F-/Hf 4+]<23.27).The structure and morphology of the deposits obtained in potentiostatic electrolysis in the one-step reduction process were analyzed and verified by X-ray diffraction,scanning electron microscopy,and energy dispersive X-ray spectrometry.In the one-step reduction process,the disproportionation reaction between the Hf metal and Hf complex ions was inhibited,and a large dendrite Hf metal was achieved in molten salt electrorefining.
基金This work was finically supported by the National Natural Science Foundation of China(No.51701221)the Major R&D Project of Liaoning province(2020JH1/10100001)+1 种基金the State Key laboratory of Metal Material for Marine Equipment and Application(No.SKLMEA-K201907)Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2019193,KGFZD-135-19-02).
文摘In deaerated 0.1 M KF solution at pH 5, pH 7.5 and pH 9, fluoride films were deposited on AZ31 magnesium (Mg) alloy at − 1.4 V vs saturated calomel electrode (SCE). The morphology, phase composition, elemental and compositional depth distribution of different fluoride films and their influences on the corrosion resistance of AZ31 Mg alloy were explored in detail. The results indicated that the films deposited at weak acidic and nearly neutral pH consisted of two layers with amorphous Mg(OH)_(2) and MgF_(2) as the inner layer, and Mg(OH)_(2), MgF_(2) and KMgF_(3) crystals the outer layer. The film deposited at alkaline pH was a monolayer structure consisting of amorphous Mg(OH)_(2) as the major constitute and MgF_(2) as the minor constitute. The protectiveness of fluoride film was intimately related to its composition and structure. The content and crystal regularity of KMgF_(3) were the two main factors influencing the protectiveness of fluoride film. The fluoride film deposited at pH 7.5 offered the best protection to AZ31 Mg alloy.
基金financially supported by the Natural Science Foundation of Zhejiang Province(No.LQ17B050002)Analysis and Measurement Foundation of Zhejiang Province(No.2015C37068)
文摘A novel electrochemical method for the rapid detection of organophosphorus pesticide residues was realized on a dual-channel screen-printed electrode （DSPE） that was integrated with a portable smartphone-controlled potentiostat. The two carbon working channels of DSPE were first modified by electrodepositing of Prussian blue. The channels were then modified with acetylcholinesterase （ACHE） via Nation. The inhibition ratio of AChE was detected by comparing the electrical current of acetylthiocholine （ATCh） that was catalyzed by the enzyme electrodes with （channel 1） and without （channel 2） organophosphorus pesticide. Inhibition ratios were related with the negative logarithm of the organophosphorus pesticide （trichlorfon, oxamyl, and isocarbophos） concentrations at optimum experimental conditions （pH 6.9 of electrolyte, 0.2V working potential, 2.5μL AChE modification amount, and 15 min inhibition time）. The linear equations were 1%=32.301gC＋ 253.3 （R=0.9750） for isocarbophos, I% = 35.991gC＋ 270.1 （R = 0.9668） for chlorpyrifos, and 1% = 33.701gC＋ 250.5 （R = 0.9606） for trichlorfon. The detection limits were calculated as 10-7 g/mL. Given that the inhibition ratios were only related with pesticide concentration and not with pesticide species, the proposed electrodes and electrometer can rapidly detect universal organophosphorus pesticides and assess pesticide pollution.
基金supported by National Natural Science Foundation of China,No.90307014
文摘A circuit model of the Amperometric immunosensor for use in the biosensor system-on-chip simulation is proposed in this paper.The model parameters are extracted with several methods and verified by MATLAB and SPICE simulation.A CMOS potentiostat circuit required for conditioning the Amperometric immunosensor is also included in the circuit model.The mean square error norm of the simulated curve against the measured one is 8.65×10^(-17) The whole circuit has been fabricated in a 0.35μm CMOS process.
文摘This paper studies the effect of expansion ratio on the corrosion rate of the expanded tubes exposed to sea water as well as the microstructure changes caused by the expansion of Cr-Mo steel tubes to large permanent deformations. 2.25 Cr-1.0 Mo steel (schedule 40 and schedule 80) tubes were subjected to various expansion ratios of 10%, 15%, 20%, and 25% by pushing conical mandrels through them using a piston. The microstructure was also studied to determine the effect of the expansion on the grain structure of the material. Microscopic examination of the expanded tubes revealed that grains elongate along the direction of the hoop stress and this elongation increases with an increase of expansion ratio. Moreover, it was found that corrosion rate and hardness increase with an increase in expansion ratio.
