Journal of Electrochemistry

Studies on Polymer Light-emitting Electrochemical Cells ——Introduction of the Studies on the Electrochemistry of Conducting Polymers in CAS Key Laboratory of Organic Solids (Ⅱ)

LI Yong-fang

2005, 11(1): 1-7.

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Polymer light-emitting electrochemical cell (LEC) is composed of a conjugated polymer(CP) / polymer electrolyte blend film sandwiched between an ITO anode and an Al cathode. When a bias voltage greater than Eg/e (where Eg is the energy gap of the CP, e is the electron charge) is applied on the two electrodes, the CP in the polymer blend film at the anode side will be oxidized (to form a p-doped region), and that at the cathode side will be reduced (to form a n-doped region), then a p-i-n junction will be produced. Light-emission occurs in the intrinsic region between the p- and n- doped layers. In comparison with the single layered polymer light-emitting diode (PLED), LEC possesses the advantages of low turn-on voltage and high quantum efficiency of its electroluminescence. But there are some drawbacks in the LEC, including slow response due to the slow ionic motion and the phase separation problem between the CP and the ionic-conducting polymer (such as PEO). Our research on the LEC focused on the electrochemical studies of the LEC and on the improvement of the device performance by overcoming the drawbacks of the LEC. Our main achievements in the studies of LECs are as follows: 1 We measured the cyclic voltammograms of a series of PPV derivatives, and calculated the HOMO and LUMO energy levels and energy gaps of the conjugated polymers. And the solid state electrochemical properties of LEC were studied for the first time. Accordingly, the electrochemical doping mechanism of the electroluminescence of LEC was confirmed. 2 The p-i-n junction structurd of the LECs was studied and confirmed by ac impedance measurements which show the flattened semicircle in its impedance plots and capacitance increase with the increase of the bias voltage. 3 In order to overcome the phase separation problem in the LECs, several kinds of bi-functional conjugated polymers possessing both electroluminescent and ionic-conductive abilities were designed and synthesized, including the PPV and PPP derivatives with PEO side chains, the block copolymers with its main chain comprised of luminescent conjugated segments and ionic-conductive segments (PEO or crown ether). The low turn-on voltage and high electroluminescent (EL) efficiency of the LECs with the bifunctional copolymers were realized: the LECs emit blue-green light with the turn-on voltage of 2.6~2.8 V and the highest EL efficiency of the LEC based on the copolymer of DMSN-TEO reached 4.2 cd/A. (4) The imidazolium salts ionic liquids with the melting points from room temperature to 80℃ were synthesized and applied in the fabrication of LECs as an electrolyte. The room temperature quasi- frozen p-i-n junction LECs were realized with the blend of MEH-PPV and the imidazolium salts ionic liquids of \\ (mp: 73 ℃)and \\ (mp: 83 ℃)as the active layer. The frozen p-i-n junction LECs emit light with fast response and high luminance.

Fabrication and Studies of a Novel Ag/AgCl Reference Electrode in High Temperature Molten Chloride Salts

GAO Pei, JIN Xian-bo, WANG Di-hua, HU Xiao-hong, CHEN Zheng~*

2005, 11(1): 8-11.

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A new method for the easy fabrication of a stable and long life silver/silver chloride reference electrode in molten chloride salts is described in this paper. The method is based on the fact that simply placing the silica glass in molten NaCl or its vapour in the presence of oxygen resulted in satisfactory conductivity for sodium ion and possibly calcium ion in the material.The performance of such made electrode has been investigated in a few typical chloride systems at temperatures ranging from 400 to 900℃. Due to the wholly sealed construction, the reference electrode is stable, temperature-reversible, contamination free to the molten salt, and re-usable in the same or different electrolyte systems.

Corrosion Behavior of Mg_(2-x)La_xNi and Mg_(2-x)Ce_xNi Hydrogen Storage Alloy

ZHANG Hai-chang, YANG Hua-bin~*,WANG Jun-hong, ZHOU Zuo-xiang

2005, 11(1): 12-15.

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The corrosion behavior of Mg-base hydrogen storage alloys has been investigated by potentiodynamic polarization and EIS. The results showed that the corrosion current density (i_(corr) ) and the electrochemical polarized resistance of Mg_(2-x)Ce_xNi alloys decreased with x increase, while i_(corr) of Mg_(2-x)La_xNi alloys increased and the electrochemical polarized resistance of Mg_(2-x)La_xNi alloys increased first, then decreased with x increase. SEM results showed that the surface of Mg_(1.85)Ce_(0.15)Ni alloy was relatively even while the surface of Mg_(2-x)La_xNi alloy had remarkedly cracks. The different behavior between Ce and La may be relevant to the structure of Ce, La oxides.

A Study of Metal Borides as High Capacity Anode Materials for Aqueous Primary Batteries

WANG Ya-dong, AI Xin-ping, YANG Han-xi~

2005, 11(1): 16-19.

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The transition metal borides VB_2 and TiB_2 were tested as high capacity anode materials and their electrochemical behaviors were studied by cyclic voltammetry and discharge measurements. The experimental results indicated that transition metal borides VB_2 and TiB_2 electrodes can deliver exceptionally high discharge capacity of over 3100 mAH/g and 1 600 mAH/g respectively, corresponding to 11- and 6-electron oxidation reaction, although their parent elements V, Ti and boron, are almost completely electrochemically inert. The different electrochemical activitis were probably due to the electrochemical activation of boron, which clamp the potential to passivation for Ti and activity for V.

Corrosion Resistance for TiO_2 Thin Films Coated 316L Stainless Steel in the NaCl Solution

SHEN Guang-xia, CHEN Yi-cong, LIN Chang-jian~*

2005, 11(1): 20-26.

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The nano-TiO_2 thin films have been deposited on the 316L stainless steel by sol-gel and the dip- coating methods. Hydrothermal post-treatment leads to crack-free coatings. Meanwhile, the surface structure and properties are optimized. Surface morphology, structure and properties are characterized by XRD, and SEM technologies. The results have shown that the surface of coatings is porous, uniform and orderly, the particle diameters are in the range of 15~18nm and the pores are about 4~8nm and TiO_2 is anatase. The results of electrochemical measurements show that in the NaCl solution with pH ≥ 2 and concentration below 1mol/L, the nano-TiO_2 coatings with thinkness 375~464nm have most excellent anticorrosion properties. Compareing with bare 316L stainless steel, the corrosion current for coating electrodes in 0.5 mol/L NaCl solution has cut down 2 magnitude and the corrosion resistance R_(p) has also decreased nearly 2 magnitude.

Anodic Polarization Behaviors of Carbon Steel in Bicarbonate Solution

ZHAO Jing-mao~*, ZUO Yu

2005, 11(1): 27-31.

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The anodic polarization curves of mild steel were measured in sodium bicarbonate solution of various concentrations, and the surface products were analyzed by XPS. Two anodic current peaks and two passive zones are observed in all the curves. When HCO_3~- ions concentration is below 0.1mol/L, the two peaks are so close that the first passive zone is difficult to be observed. When HCO_3~- ions concentration is above 0.1 mol/L, the first peak appears clear, while the second becomes smaller. The XPS results indicate that the out layer of film formed at a higher potential is mainly composed of Fe_2O_(3,) and the inner film is a mixture of ferrous and ferric oxide.

In-situ Measurements of Single-stranded DNA Hybridization and Cleavage by Quartz Crystal Microbalance

ZHU Long-zhang, GAO Yu-xiang, SHEN He-bai~*, YANG Yong-tao, YUAN Lian-qun

2005, 11(1): 32-36.

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The use of quartz crystal microbalance (QCM) for in-situ monitoring the immobilization of single-stranded DNA(oligo-1), marked with mercaptol group at 5′ end, on the surface of gold-filled 7.995 MHz AT-cut quartz crystal by Au-S bond with self-assemble technique is reported. And then the hybridization of ssDNA with the complementary 10-mer ODN(oligo-2) and 8-mer ODN(oligo-3) is described. Moreover, the QCM has been employed to analyze the DNA cleavage by cerium(IV) ions under moderate conditions. The results showed that the QCM, which is capable of sensitive measurement, was able to in-situ investigate immobilization, hybridization and cleavage of ssDNA. And the cerium(IV) ions had no cleavage for the double-stranded DNA, but it could hydrolyze single-stranded DNA. So the hydrolytic cleavage of ssDNA at the specific site could be realized by the protection of the hybridization.

Fabricationand Propertiesof Hydrophilic Thin MEA Used in PEMFC

MA Jian-xin,YI Bao-lian~*,ZHANG Hua-min

2005, 11(1): 37-41.

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In this paper, a hydrophilic thin MEA with 0.4 mg/cm~2of Pt loading in a cathode was fabricated by a novel method, and its morphology and electrode performance were compared with those of a conventiona hydrophobicl MEA with 0.7mg/cm~2of Pt loading. Unlike the morphology of the conventional MEA, there were lots of stalactiticmicro-particles on the surface of the thin MEA, which increases the specificsurface of the catalyst layer in the electrode markedly. The electrochemical results showed that in the range of small current density (<1A/cm~2), the performance of the thin MEA was inferior to that of conventional MEA, while in the range of large current density (>2A/cm~2), the performance of the former was superior to that of the latter. The maximum specific power of the thin MEA was 1.23W/cm~2, which is higher than that of conventional MEA (1.19A/cm~2). Furthermore, the specific activity of Pt in thin MEA was higher than that of conventional MEA in the range of large current density.

Study on the New Technique of Cu Micro-plating Based on Ceramics

GU Zhi-jun~

2005, 11(1): 42-45.

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By combing the computer processing system (including the design of the line and the pattern, the choice of the scanning area and the treatment of the activation) with the electroless-plating technology, this article provides a new approach for the micro-plating based on the ceramics. The copper film based on ceramics with good properties can be obtained under the mild operating conditions. The line resolution is 35 μm and the wiring speed is 50 mm/s. The results had also showed that the quality of the copper plating is closely related to the roughness of the ceramic substrates.

The Mechanism of the Improvement on Cycling Performance and Thermal Stability of LiNi_(0.8)Co_(0.2)O_2 by Ti-doping

LIU Han-san, LI Jie, GONG Zheng-liang, ZHANG Zhong-ru, YANG Yong~

2005, 11(1): 46-52.

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Improved cycling performance and enhanced thermal stability were observed for Ti-doped LiNi_(0.8)Co_(0.2)O_2 cathode materials. The mechanism of these positive effects was investigated in this work. The improved cycling performance of Ti-doped cathodes is ascribed to the suppression of phase transitions and lattice changes during cycling, and the decrease of interfacial reaction activity between the cathode and electrolyte. The enhanced thermal stability of Ti-doped cathodes is attributed to the suppression of thermal decomposition reaction of delithiated cathode material, which will produce heat and oxygen gas as the cause of electrolyte decomposition and combustion reaction.

Preparation and Characterization of LiNi_(0.85)Co_(0.10)(TiMg)_(0.025)O_2 as Cathode Materials for Lithium-ion Batteries

ZHU Xian-jun, CHEN Hong-hao, ZHAN Hui, YANG Dai-ling, ZHOU Yun-hong~*

2005, 11(1): 53-57.

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Cathode material of LiNi_(0.85)Co_(0.10)(TiMg)_(0.025)O_2 were prepared by solid state reaction at 725℃ for 24 h from LiOH·H_2O, Ni_2O_3, Co_2O_3, TiO_2 and Mg(OH)_2 under flowing oxygen, and were characterized by TG-DTA, XRD, SEM and electrochemical tests. Effort to simultaneously doped LiNiO_2 with Co-Ti-Mg has been tried to improve the cathode performance. The results show that co-doping definitely has a large beneficial effect in increasing the capacity (182.7mAh/g of the first discharge capacity for LiNi_(0.85)Co_(0.10)(TiMg)_(0.025)O_2) and cycling behavior (175.5 mAh/g after 10 cycles). This cathode materials can be applied for lithium-ion batteries.

Influence of Rare Earth Oxide on the Performance of Secondary Zinc Electrodes

MENG Xian-ling, YANG Hua-bin~*, WANG Jun-hong, ZHOU Zuo-xiang

2005, 11(1): 58-61.

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Influence of La(OH)_(3 )or Ce(OH)_3in secondary zinc electrode was investigated by the cyclic voltammetry, potentiodynamic polarizationand potentiostatic polarization tests and influence of La_2O_3or CeO_2in the charge/discharge performance of Zn/Ni battery was studied by galvanostatic charge/discharge experiment. The results showed that the film of rare earth hydroxide prevented the zincate species from transferring toward solution, enhanced hydrogen overpotential and decreased thecorrosion current density (i_(corr)), and therefore inhibited zinc corrosion. The potentiostatic polarization results at100mV overpotential showed thatLa(OH)_3or Ce(OH)_3coated on the zinc electrode effectively suppressed the zinc dendrite growth. The La_2O_(3 )or CeO_2addition to the calcium zincate electrode improved the cycle performance of Zn/Ni battery.

Electrochemical Performance of Gel Polymer Electrolyte Prepared by Thermal Initiating Polymerization of Acrylates

PIAO Jin-dan,YUAN Li-xia,AI Xin-ping~*,YANG Han-xi,CAO Yu-liang

2005, 11(1): 62-66.

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A gel polymer electrolyte was prepared by thermal initiating polymerization of the acrylates in the EC/EMC/DMC electrolyte solution at 100℃. The LiCoO_2/MCMB polymer cells were assembled and their electrochemical properties were evaluated at various charge-discharge rate and temperatures. The ionic conductivity of the polymer electrolyte containing 85wt.% liquid electrolyte is around 3.2×10~(-3)S·cm~(-1) at 20℃ and 5.6×10~(-4)S·cm~(-1)at -30℃ respectively. The gel polymer electrolyte has good electrochemical stability up to 4.5V versus Li/Li~(+).The first charge-discharge efficiency of the polymer cell at 0.2C rate is almost 92.1%. The discharge capacity of the cell at 1.0C rate is 95% of the capacity at the 0.2C rate and the discharge capacity of the cell at -20℃ is 72% of the capacity at the 20℃. The charge-discharge capacity of the polymer cell is stable with charge-discharge cycling.

The Electrophoretic Deposition of Nano Hydroxyapatite Coating on Titanium Surface

CHEN Fei~1,LIN Chang-jian~

2005, 11(1): 67-71.

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A hydroxyapatite coating with nano-structure on the roughened titanium surface was prepared by electrophoretic deposition process. To decrease sintering temperature the HAp nanoparticles synthesizedby a wet chemical method was used. It is observed that the coating is uniform without cracks. After sintering the nano-strueture of HAp coating remains unchanged. The surface treatment of Ti is applied to form a distribution of small pits and TiO_2thin layer that improve the adhesion of coatingto Ti substrate. It is shown that the bonding strength of coating is as high as 18±2.5MPa. The hardness and Young's modulus are 40.6 and 0.42 GPa, respectively.

Calcium Zincate Prepared by Ball Mill Method

LI Sheng-xian~*,TIAN Shuan-bao,ZHU Shao-shan

2005, 11(1): 72-76.

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Calcium zincate was prepared by ball milling method and the factors that influence its synthesis were investigated. The composition of the compound was Ca(OH)_2·2Zn(OH)_22H_2O, which was verified by XRD and TG-DTA methods. The results of powder microelectrode and in simulated batteries showed that the material had excellent cyclic performance.

Application of Carbon Paste Electrode on the Electrogenerative-leaching Process of Sulfide Minerals

WANG Shao-fen~

2005, 11(1): 77-82.

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The cyclic voltammetry curves of sulfide mineral electrodes or corresponding carbon paste electrodes in NaCl electrolytes have been obtained in this study. The experimental results indicate that acetylene black (revealed) the electro-catalytic propertyin the electrogenerative-leaching process of sulfide minerals. The output currentand potential of carbon paste electrodes were increased to some degrees while the activation energies were lower.

Preparation and Electrochemical Property of AAO Nano-channels Filled with NiO

GU Chi, Yan Jun-mei, Yang Yong~

2005, 11(1): 83-86.

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The AAO template with nano-channels was synthesized and filled with transient metal-oxide NiO by sol-gel method, and their electrochemical properties were primarily studied. The results showed that the porous nano-channels were well defined with the diameter about 50nm. The nano-structured NiO was filled into the template's nano-channels successfully., Cyclic voltammetry studies show that the NiO in AAO template has good cycle stability.It was suggested that the AAO-metal-oxides composites could be used as novel anode materials for Lithium ion battery.

The Fabrication and Electrochemical Studies on Carbon Nanotube Array Electrodes

GAO Quan-yong, ZHANG Jing, YANGYong~*

2005, 11(1): 87-91.

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An improved technique for fabrication of carbon nanotube array electrodes has been proposed in this work. Firstly, carbon nanotubes (CNs) array electrodes were prepared by combsination of Chemical Vapor Decomposition (CVD) method and sputtering techniques in anodized aluminum oxide (AAO) membrane. The CNs/AAO was immersed into HF solution to remove the barrier layer. Controlling the immersing time, the CNs array electrodes with different length contacted with electrolyte can be prepared. The morphology of CNs array electrodes was observed by SEM. The electrochemical properties of CNs array electrodes were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Cyclic voltammetric curves of CNs array electrodes showed that the peak at about 1.0 V is increasing by the prolonging of the immersing time. But it changes slightly when the immersing time is more than 15min. It was anticipated that the main intercalation behavior of Li-ions in carbon nanotubes happens through the holes of ends of carbon nanotubes. The results of dynamic capacitances-potential curves showed that there is an anodic peak at about 1.0 V is which is corresponding to the Li~(+) intercalation process. It indicates a possible application of CNs array electrodes can be explored as electrochemical super-capacitors in Li-ion battery electrolytes.

Preparation of Poly ( Bromophenol Blue ) Modified Glassy Carbon Electrode and its Electrocatalytic Activity

CHEN Wei,LUO Hong-bin,LIN Xin-hua~*

2005, 11(1): 92-95.

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A film of poly ( bromophenol blue ) was formed on a glassy carbon electrode by using cyclic voltammetry. A stable film could be obtained with a potential range from -1.0V to +1.8V(vs.Ag/AgCl). The experimental results showed that the poly ( bromophenol blue ) modified glassy carbon electrode could catalyse the oxidation of ascorbic acid. It decreased the oxidation potential by about 270mV but increased the peak current. Meanwhile, this electrode showed a good linear current response for the ascorbic acid range from 2.5 to 250 (g/mL.)

Electrochemical Properties of Polymeric Gel Electrolyte with GBL/EC as Plasticizers

LIU Yu-wen,ZHANG Yong,LI Xiao-long,GU Qi-ping,ZHANG Cui-fen,HUANG Yu-dong

2005, 11(1): 96-100.

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Polymeric gel electrolytes (GPE) based on PMMA and PVDF-HFP were prepared using the binary mixtures of γ-butyrolactone (GBL) and ethylene carbonate (EC) as plasticizers. The ionic transport properties and electrochemical stability were studied. The room temperature conductivity reached 1.2 mS·cm~(-1), electrochemical stability window exceeded 4.5V. The interfacial stability between GPE and lithium electrode was also investigated. The lithium metal polymer battery (LMPB) prepared with the GPE showed better charge and discharge life cycle when the the lithium metal electrode was treated with 1,4-dioxane.

Research on Phenol Wastewater Treatment by Electrochemical Oxidation

LI Tian-cheng, ZHU Shen-lin

2005, 11(1): 101-104.

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Electrochemical oxidation is an effective technology for the phenol wastewater treatment, and the anode properties are important to the electrochemical oxidationefficiency. The over-potentials of oxygen evolution have been measured for thestainless steel, feasible graphite and SnO_2/Ti anode respectively. Moreover, the synthetic phenol wastewater was treated by the electrochemical oxidation with the stainless steel or feasible graphite anodes. The experimental results showed that the order of the over-potential is SnO_2/Ti > graphite > stainless steel; meanwhile, the COD values of purified water were approaching to or less than 100 mg·L~(-1), and the phenol concentrations in the purified water were below 0.5 mg·L~(-1).

Polarographic Method of Acid Cyanine 5R and the Supramolecular System of Acid Cyanine 5R with Cyclodextrins by Polarography

LU Fei,PAN Jing-hao~*,WANG Ying-te,GUO Yu-jing

2005, 11(1): 105-109.

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The polarographic method was employed to investigate the supermolecular system of acid cyanine 5R and with cyclodextrins. It was shown that the reducing peak formed by AC 5R in Na_2HPO_4-KH_2PO_4 solution at pH=7.0 was well-defined, stable and sensitive with a peak potential near -0.60 V (vs. SCE). Variations of AC 5R concentrations with the peak currents and the peak height of second derivative polarographs fell in the linear regions of 3×10~(-8)～6×10~(-5) mol/L (r=0.9926～0.9991). The determining limit was 6×10~(-9) mol/L, RSD was 1.16%(n=10) and the standard recovery was 95.9%～103.3%. The polarographic method established is capable of application in the quantitative analyses of AC 5R. In addition, the effects of various cyclodextrins on the electrochemical behavior of AC 5R were also studied. The inclusion constants were calculated by electric current method, and possible factors which influence the inclusion of AC 5R and various of cyclodentrins are discussed.

The 9~(th)National Meeting of Organic Electrochemistry and Industry Has Been Held Triumphantly

2005, 11(1): 112-112.

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