Journal of Electrochemistry

Innovation in Molten Salt Electrochemistry

WANG Di-hua, CHEN Zheng~*

2005, 11(2): 119-124.

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Recent research development in molten salt electrochemistry at the Electrochemical Research Centre of Wuhan University is briefly reviewed. Attention is first paid on the preparation of silicon and its binary alloys, as well as oxide based functional materials. In addition, the quartz sealed Ag/AgCl reference electrodes suitable for high temperature molten salts are described. Focus is also given to two types of metal based cavity electrodes that are capable of loading micrograms of oxide powders and hence allow fast and reproducible measurements for the electrochemical behaviour of the powders in molten salts. The article finishes by highlighting the concept of “three-phase interline electrochemistry” in conjunction with reporting the preliminary results from the investigation of a simple "thin layer model" for the electrochemical reduction of solid AgCl in aqueous solution and solid SiO_(2)in molten salts.

Fabrication of Nano Capacitor and its Electrical Properties

LIU Ling, ZHOU Qin, JIA Neng-qin, JIANG Zhi-yu~*

2005, 11(2): 125-128.

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A step-by-step assembling method was developed for preparing nano capacitors using anodic aluminum oxide (AAO) membrane as templates. The nano capacitor consisted of three parts: electrochemically polymerized PPy electrode/ el ectrochemically precipitated porous TiO_(2) separator / chemically polymerized PPy electrode, and demonstrated the charge/discharge behavior as a typical electrochemical supercapacitor with good cyclic ability.

Electrochemical Stability of PVA Alkaline Gel Polymer Electrolyte Membranes

WANG Jun-hong, LIU Jian-min, YANG Hua-bin~*, ZHOU Zuo-xiang

2005, 11(2): 129-132.

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Polyvinyl alcohol (PVA) alkaline polymer gel electrolyte(GPE) membranes were successfully prepared by a solution-casting technique and their electrochemical stabilities were investigated. The electrochemical impedance spectrum (EIS) results showed that the ionic conductivity of the PVA alkaline GPE membranes first increased with the increase of KOH content, then decreased with the further increase of KOH. When the weight percentage of the KOH in the PVA alkaline GPE membrane approached to 42%, it exhibitedthe highest ionic conductivity of 2.01×10~(-3 ) S/cm at room temperature (R.T.). The X-ray diffraction (XRD) results revealed that with the increase of KOH the crystalline of the PVA was disrupted and converted into an amorphous phase. While the ionic conductivity decreased due to the increase of the amorphous unionized KOH in the membranes with the further increase of KOH. The cyclic voltammograms (CV) and Raman spectra indicated that the GPE membranes had promising electrochemical stabilities. It is suggested that the PVA alkalineGPE membranes could be used for practical applications in alkaline rechargeablebatteries.

A Preliminary Study of Electrocrystallization of Bismuth on Glassy Carbon

YANG Min-li, ZHANG Zhan-jun~*

2005, 11(2): 133-139.

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The electrocrystallization of bismuth on glassy carbon electrodes (GCEs) from nitrate solutions was studied by cyclic voltammetry and chronoamperometry. Cyclic voltammograms exhibit a crossover between the cathodic and anodic branches, characteristic of the formation of bismuth nuclei on GCEs, and show that the bismuth electrocrystallization on GCEs is a diffusion-controlled reaction. The current transients were analyzed with the Scharifker and the Heerman equations. With the increaseof Bi~(3+)concentration, the non-dimensional plots leaned to the theoretical curve for 3D instantaneous nucleation and growth. The overpotential dependence of nucleation and growth mechanism was also found. With the increase of overpotential, the non-dimensional curve approaches closer the limit for 3D instantaneous nucleation and growth. A quantitative analysis further shows that the nucleation rate constant (A) and the number density of active sites (N_(0 )) exponentially grow with the increase of overpotential, and the diffusion coefficient (D)decays in an exponential mode, which was not reported before. A comparison between the kinetic parameter values obtained from the Scharifker equation and those from the Heerman equation was made, showing the very close N_0 and Dvalues and the distinct Avalues (especially at -300 and -350 mV). However, under the experimental conditions of this work, both of the equations can be used for describing the electrocrystallization of bismuth on GCEs.

A Comparison on Structural Sensitive Adsorption of Sb on Au Single Crystalline Electrodes

YANG Jia-wei~*,SHANG Wang-huo, WU Qiong, MAO Bing-wei

2005, 11(2): 140-145.

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We compare the behaviors of irreversible adsorption of Sb(III) and its reduction, underpotential deposition of Sbon Au(111) and Au(100) as well as mutual interactions of the processes. Based on in-situ scanning tunneling microscopic and cyclic voltammetric results, the substrate structure not only influence anion adsorptionbehavior and thus the Sb adsorption structure, but also the stability of its own structure. On Au(111) surface,the irreversibly adsorbed dense and disordered SbO~(+ )film structure remains after reduction of the film; while on Au(100)surface, due to the coadsorption of SO_4~(2-),an ordered(2×2)structure is formed after reduction.UPD of Sb on Au(111)is accompanied by significant surface alloying, which destroys the ordered structure of the Au (111) surface;while on Au(100)surface,the lattice type and lattice constantare in good match with that of the (100)plane of the stable AuSb2 alloy. Therefore the interaction between Au and Sb appears in the form of ordered surface compound, and surface alloying can be avoided during the process of UPD. The results further reflect the sensitivity as well as importance of the substrate structure.

The Preparation and Performance of The Aqueous Matrix for Molten Carbonate Fuel Cells

LIN Hua-xin~

2005, 11(2): 146-151.

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PVA matrix of MCFC was prepared from the α-LiAlO_(2 )powder, and polyvinylalcohol(PVA), Compared with the conventional PVB matrix, higher porosity,higher thermal weight loss and smaller maximum pore diameter were achieved for PVA matrix. Single cell was assembled with PVA matrix. At reaction gas pressure of 0.9MPa, under reaction gas utilization of 20%, at 300 and 428.57mA·cm~(-2), the cell voltage was 0.849 and (0.739) V respectively, and the output power density was 254.7 and 316.7mW·cm~(-2 )respectively, which are higher than those of the cell assembled with PVB matrix. During thermal cycles, the cell performance shows a slightly decreasing-rising-stabilizing process, which might be due to the conductivity variation of PVA matrix resulted from the losing of hydrated water in it at high temperatures.

The Synthesis, Characteristics and Performance of CNT Composites as Anodic Materials in Litium-ion Battery

DONG Quan-feng~*, ZHENG Ming-sen,HUANG Zhen-cai,JIN Ming-gang,ZHAN Ya-ding, LIN Zu-geng

2005, 11(2): 152-156.

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As an anodic material for lithium ion battery the carbon nano-tube (CNT) and some compounds based on tin have ever been investigated intensively. The fruited progress has not been made yet, however. In this paper the composites of CNT and Sn/SnO_(2)were synthesized employing two methods and characterized by SEM and XRD. And the electrochemical performance of the composites was investigated.

Study on the New Type Fe_3O_4 composite Anode

XIONGXin-yong~

2005, 11(2): 157-161.

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An ultrafine powder of magnetite has been prepared, and used to prepare the composite anode of Fe_(3)O_(4)-Fe by sintering method. The voltage of chlorine evolution、polarization curves、service life and mass loss, and the optimum sintering temperature and the weight ratio of the sintered powder have been investigated. All results showed that the method of preparing the practical Fe_(3)O_(4)-Fe composite uniform anode is feasible.

Preparation and Characterization of MCM-41/ PVdF-HFP Composite Microporous Polymer Electrolytes for Li-ion Batteries

CHEN Zuo-feng~

2005, 11(2): 162-166.

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MCM-41/vinylidine fluoride-hexafluropropene copolymer (PVdF-HFP) composite microporous polymer electrolytes were prepared with mixed solvent of N, N-Dimethylformamide (DMF) and acetone. The influence of MCM-41 and nano-SiO_(2) on the porous structure of the microporous polymer electrolytes were studied with SEM. The results show that MCM-41 could take the place of the plasticizer in the process of making pores, and bring the preparation of microporous membranes easily. The preliminary electrochemical tests showed that the ion conductivity of composite microporous polymer electrolyte with 10% MCM-41 was about 10~(-3) S cm~(-1), and the performance of batteries was improved. The mesoporous MCM-41selected in the paper possesses the framework unit of SiO_(2), that is widely used as inorganic filler in polymer electrolyte. In addition, it possesses the particular channels arranged in hexagonal array and a large surface interstice as stacking, that could lead to the formation and connectivity of micropores, finally a higher ion conductivity. These properties make MCM-41 the favorable and promising inorganic filler in polymer electrolyte.

Potential Fluctuations of 7075 Aluminum Alloy under Thin Electrolyte Layers

CHEN Su-jing~

2005, 11(2): 167-171.

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Lens tissues adsorbing 3.5% sodium chloride solution were used to simulate thin electrolyte layers. The 7075 aluminum alloy was immersed under the thin electrolyte layers for 0, 4, 6, 8 and 12 h respectively. Then the fluctuations of natural-corrosion potentials of the alloy were monitored. The fluctuations of natural-corrosion potential were observed rather small in the initial corrosion stages after 6h immersion, and the positive peaks of potential appeared. However the amplitudes reached 20mV after 4h and 12h immersion. The RMS of natural-corrosion potentials decreased with corrosion time at first and then increased. It reached a minimum at 4 h. The k value (slope of linear part) was rather high at 6h. Thus it can conclude from above that the initiation of pitting happened after 6h corrosion.

Application of Nickel foam Electrode for Electroreduction Intermediate of Purine

YANG Hui-wen~*, HU Xi-en,WANG Xue-jun

2005, 11(2): 172-175.

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Nickel foam with weight uniformity, good porosity ,pore size and low resistivity as a three-dimensional cathode was used in a filter-press electrochemical reactor. The H_(2)SO_(4) as supporting electrolyte, separator of cation ion exchange membrane, and the lead plate as an anode were used. The cyclic system consisted of electroreduction reactor, pump, store tank and ampere meter. NAU was electroreduced in the cathode chamber of the reactor. Purine intermediate was synthesized with DAU, and the results were compared with those of iron powder reduction process. A peak current in the electroreduction process was detected. The current density of nickel foam increased by 77.3%~86.7% than that of using plate nickel. The average current efficiency was 90.3% and average conversion of NAU was 98.4% , and average energy consumed was 2.92 kWh/kg, respectively. The Purine yield of electroreduction was similar to that of using iron powder.

Investigation on Ru-Ti-Ir-Sn Oxide Anode Coatings for Electrolyzing Seawater

WANG Ke~

2005, 11(2): 176-181.

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The anode coatings of Ru-Ti-Ir-Sn oxide with various compositions were prepared by thermal decomposition. The physical and electrochemical properties of the coatings were characterized by scanning electron microscope (SEM), energy dispersive X-ray detector (EDX), accelerated life, current efficiency, anti-Mn~(2+)contamination, polarization curveandcyclic voltammetry tests. The results showed thatthe anode coating with optimized formula possessed excellent overall properties for electrolyzing seawater.

Ni-Mo-P Alloy by Electroless Deposition and its Properties

WANG Sen-lin~

2005, 11(2): 182-187.

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The electroless Ni-Mo-P alloy has been deposited from the alkaline bath containing boric acid as a buffer agent and sodium citrate as a complexing agent. The effect of deposition parameters, such as pH and concentration of (NH_(4))_(6)Mo_(7)O_(24)4H_(2)Oon the plating rate, the composition, the structure and the microhardness of the coating was examined. It was found that the presence of molybdenum has an inhibitory effect on the alloys deposition. As a consequence, the percentage of molybdenumin the Ni-Mo-P coatings never reaches high values, which was lower than 20 at%. It was also shown that the deposition condition affects the microhardness of the deposit and almost does not affect the structure of the deposit. Therefore, the microhardness of the deposit depends on the content of molybdenumin the deposit. The corrosion resistance of the deposit in 3.5 Wt% NaCl solution (pH 7.0) was studied by the weight loss test and the electrochemical anodic polarization measurement. The results show that the corrosion resistance of the deposit is better and depends on the deposition parameters, and the weight loss test agree with those of the anodic polarization measurement.

Structure and Corrosion Electrochemical Properties of Self-assembled (3-Mercaptopropyl) Trimethoxysilane Films on Copper Electrode

HUANGLing~*,LINKe-fa,YANG Fang-zu, XU Shu-kai, ZHOU Shao-min

2005, 11(2): 188-192.

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A self-assembled monolayer of (3-mercaptopropyl) trimethoxysilane(MPTS) was formed on a electrochemical polished copper surface electrode. The corrosion protection abilities of the monolayer were evaluated in 5% NaCl solution using electrochemical linear polarization. The effects of deposition time and silane concentration on corrosion of copper were also discussed. The surface structure of MPTS films was measured by FT-IR and SEM. It was found that the corrosion resistance of copper was reduced markedly owing to the MPTS monolayers formation on copper. The MPTS monolayer retarded the reduction of dissolved oxygen and inhibited the growth of copper oxide in the NaCl solution. FT-IR results indicated the linkages of siloxane on copper suraface. The presenceof (CH_(3)O)_(3)Si (CH_(2)) _(3)SHincreased the inhibition efficiency at every concentration.

Selective Electroless Copper Plating Micro-pattern on Ceramics Without Sensitisation and Activation

XU Zhen-lin~

2005, 11(2): 193-198.

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The purpose of this article is to provide a new technology of electroless copper plating without palladium activation steps. By combining the technology of laser micro-etching with the new copper-plating bath, copper plating on ceramics was obtained. The experimental results showed that the solution used for copper electroless plating was stable and the copper coating obtained was bright,dense with good electrical conductivity.The line definition was about 40 μm. The electroless Cu films deposited from this system were gentle and required simple operating conditions.

Study on Synthesis of m-phenoxy Benzoic Acid by Electrolysis Oxidation Method

XU Wei~*,ZHAO Chong-tao

2005, 11(2): 199-203.

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The m-phenoxy benzoic acid was synthesized by oxidation m-phenoxy toluene using Cr(Ⅵ)as oxidation media, which was prepared by electrolysis oxidation of Cr(Ⅲ)in the electrochemical bath using Nafion 417 as a diaphragm, Pb-PbO_(2) as an anode and Pb as cathode. The effect factors on the electrochemical oxidation of Cr(Ⅲ)to Cr(Ⅵ)in this electrolysis were studied. Furthermore, the optimal conditions for electronic synthesis of m-phenoxy benzoic acid were also discussed.

Using Electrodeposition to Fabricate Mould for Polymer Microfluidic Chip

LUO Yi~

2005, 11(2): 204-207.

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Many researches have been focused on polymer microfluidic chip in recent years and the mould plays an important role in its fabrication process. Using electrodepositingmethod to fabricate a metal mould for polymer microfluidic chip has been presented in this paper. An ultra-thick photoresist SU-8 was coated on a pretreated metal plate, after photolithography, nickel was electrodeposited in the patterned SU-8, then was removed the SU-8 to obtain a final metal mould. This methodreduces workload of electrodeposit largely. Applying counter current before deposit, adding additive to solution and vacuum anneal after demould have been used to improve the binding force between Ni substrate and electrodeposit structure.

The Effect of Oxidant on Structure and Properties of PAn/PTFE Conducting Composite Membrane

TAO Chang-yuan~

2005, 11(2): 208-214.

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The PAn/PTFE conducting composite membrane was prepared by means of in-situ permeating chemical polymerization, with (NH_(4))_(2)S_(2)O_(8) and Na_(3)VO_(4) being used as an oxidant respectively.The polymerization-growth behavior of the aniline by using different oxidant was compared. In addition, the oxidant effect on the structure and properties of conducting composite membrane was discussed. The results of SEM micrographs, pore size distribution and electrochemical methods suggested that using either oxidants could also induce the product with small pore size and dense pore structure. Compared with (NH_(4))_(2)S_(2)O_(8), using Na_(3)VO_(4 ) as an oxidant would induce the polyaniline with denser polymers in the membrane pores, the surface conductivity was 2.62 S·cm~(-1), while the cross-sectional conduction was enhanced about 1~2 orders, and the electrochemical activity of such conducting composite membrane were enhanced also.

Influence of DC Electric Field on the Oil-water Relative Permeability in Water-drive Reservoir

ZHANGJi-hong~

2005, 11(2): 215-218.

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The effectsof DC electric field strength and direction on oil-water relative permeability and the influence mechanism in reservoir were studied and analysed.The results of experiments indicated that, with the application of external electric field, the core samplesbecomes more hydrohilic, irreducible water saturation increasesand residual oil saturation decreases. Meanwhile, oil relative permeability increases and water relative permeability decreases with increasingof the strength of external electric field. It is demonstrated as well that the different seepage flow behaviors, the structure change of double-electric-layer surface and the electric-viscous effect of polar and non-polar phaseare the main factors influencingoil-water relative permeability.

Preparation, Characterization and Electrochemical Properties of Nano TiO_(2)-CNT-Pt on Ti Substrate Complex Electrode

CHU Dao-bao~

2005, 11(2): 219-223.

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The nanoTiO_(2)-CNT-Pt on Ti substrate complex electrodes were prepared from precursor of (Ti(OEt)_(4)) directly hydrolyzed and by cyclic voltammograms electroplating method . The XRD and SEM results showed that the nano TiO_(2) (anatase) particle sizes ranged 5~10 nm and the Pt nanoparticle (average size 9nm) dispersed uniformly on nanoTiO_(2)-CNT film surface. The electrocatalytic activity of Ti/nanoTiO_(2)-CNT-Pt electrode was investigated by cyclic voltammetry and chronopotentiogram. The results indicated that the Ti/nanoTiO_(2)-CNT-Pt electrode exhibited very high electrocatalytic activity and stability for the electro-oxidation of methanol at room temperature. When Pt loading was 0.32 mg/cm~(2), the oxidation peak current of methanol was 480 mA/cm~(2).

Oscillographic Determination of Ethamsylate

NI Hong-gang, ZHANG Hong-fang, ZHENG Jian-bin~*

2005, 11(2): 224-227.

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In 0.2 mol L~(-1) NaOH solution, ethamsylate can yield a sensitive incision on cathodic branch of dE/dt-E osillogram at 0.3V (vs. SCE). Based on the oscillographic characteristic, a second order differential simple oscillographic voltammetry for determination of ethamsylate in tablet and injection is presented in this paper. The peak height on second order differential simple oscillographic voltammogram is linearly proportional to concentration of the ethamsylate in the range of 1.5×10~(-5)～3.4×10~(-4) mol·L~(-1 )with a 0.9921 correlation coefficient and a detection limit of 6.0×10~(-6 )mol·L~(-1 ) for ethamsylate. The relative standard deviation is 2.1% for the determination of 3.0 10~(-5) mol L~(-1) ethamsylate (n=5). Compared with HPLC and other methods, the second order differential simple oscillographic voltammetry is a convenient method due to its cheap equipment and rapid measurement.

Initial Process of Pyrophosphate Copper Electroplating

FENG Shao-bin~*, SHANG Shi-bo, FENG Li-ting

2005, 11(2): 228-231.

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The relationship between the type of on changes of copper electroplating potential~time and the adhesion of coating layer was examined by chronopotentiometry. The conception of critical initial current density (D_(KC)) was put forward. When the initial working current (D_(KI)) was higher than the critical initial current, the iron electrodewas polarized to activation potential of iron surface firstly, then to the activation of the substratesurface, and finally to depositionpotentialof copper ion. The coating deposited on the active surface and had goodadhesion.On the contrary,when D_(KI) was lower than D_(KC), the coating deposits on the surface of "passivated" iron substrate, and bad coating was only gained. The combinationof Ar ion sputtering and X radial photoelectron spectra may measure the existence ofoxygen layerbetween copper coating and iron substrate. Through adjusting technical condition, the optimal process of pyrophosphatedirection copper plating was given.

Index of Recent Literatures in ElectrochemicalTechnique and its Applications

2005, 11(2): 233-236.

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