Materials Science and Engineering Commons^™

Studies On Methods Of Fuel Cells Electrodes Preparation, Jun Gu, Sheng Sui, Guang-Qiang Li, Zhitong Sui

Journal of Electrochemistry

In fuel cells, the structure of electrodes is an important factor which effect the cell performance. To improve the structure and the performance of electrodes, a new method of providing fuel cell electrodes is proposed in this paper. PTFE (polytetrafluoroethylene) and ethyne black was ground for about half an hour in a high-speed grinder, then the catalyst was added into the grinder and milled for an hour. This milled catalyst was transferred into a mixer followed by the addition of surface-active agent. After a suspension was formed, it was filtered under vacuum condition.Then a thin uniform filter-cake of the catalyst …

Study On Electrochemical Reduction Properties Of Nitrobenzene, Chu-Na Ma, Wen-Kui Zhang, Hui Huang, Yong-Ping Gan

Journal of Electrochemistry

The electrochemical reduction characteristics of nitrobenzene was extensively investigated by using the techniques such as quasi-steady-state polarization, cyclic voltammetry, fast linear potential sweep method and chronoamperometry in this paper. The electroanalytic properties of Cu, Cu-Hg and Cu-Ni electrodes were evaluated. Based on the study of the transient steping behaviour of nitrobenzene to PAP, the reduction mechanism was discussed. The results showed that the transition steps existed on the electrochemical reduction of nitrobenzene in acidic solution, the reactant is also absorbed on electrodes surface. The control step in the reduction of nitrobenzene was ascribed to the diffusion of nitrobenzene and its …

High Performance Proton Exchange Membrane Fuel Cells, Jing-Rong Yu, Bao-Lian Yi, Ming Han, Xiao-Liang Cheng, Zhi-Gang Shao, Jing-Xin Zhang

Journal of Electrochemistry

Proton-exchange membrane fuel cells(PEMFC) using a perfluorosulfonic acid proton exchange membrane as an electrolyte can simplify water and electrolyte management. In this paper, the effects of thickness of PEM on the performance of PEMFC were studied. The Nafion-112 PEM and low platinum loading E-TEK electrode yielded very high power density, of the order of 0.95 W/cm². The energy-conversion efficiency, the degree of platinum utilization and stability for PEMFC using Nafion 112 and E-TEK electrode were also investigated.

Photoelectrochemical Studies On The Tio2 Nanostructured Porous Film Sensitized By Cyanine Dye, Li Zhang, Mai-Zhi Yang, Xue-Bin Qiao, Yan-Zhong Hao, En-Qing Gao, Sheng-Min Cai

Journal of Electrochemistry

The photoelectrochemical behaviors of the TiO₂ nanostructured porous film sensitized by cyanine dye were investigated in this paper. The results showed that the excitaed state level matched the conduction band edge of TiO₂ nanoparticle. Therefore the sensitization of the dye can increase the photocurrent intensity of the TiO₂ nanostructured electrode obviously and results in a red-shift of optical absorption from the ultra-violet region to the visible. As a result, the light-to-electricity conversion efficiency was improved evidently, the maximum value of IPCE has reached 12.1%.

Investigation Of Sodium Hypophosphite Anodic Oxidizing Behavior In The Process Of Acid Electroless Nickel Deposition, Mei-Yuan Wang, Ya-Fei Kuang, Yan Xu

Journal of Electrochemistry

The anodic oxidizing behavior of sodium hypophosphite in the process of electroless nickle deposition (pH=5.5) was investigated with the linear potential sweep method and alternating current impedance. The results indicated that, the oxidation of NaH₂PO₂ was a complicated electrochemical process and affected by the concentration of NaH₂PO₂, the temperature of the bath, the sweep rate and the existence of nickel ion. The NaH₂PO₂ electrooxidation reaction was very likely preceded by heterogeneous interface transformation process, which might be the control step of the whole anodic process.

Studies Of The Electrode Preparation Of Electrode From Lead Carbonate For Lead Acid Batteryⅰ. The Activation Of The Pme, Zhong-Xu Dai, Di-Hua Wang, Jun-Wei Jiang, Yun-Hong Zhou, Jin-Yun Zou

Journal of Electrochemistry

Lead carbonate which was an intermediate product in lead hydrometallurgy without pollution of lead vapor and sulfur dioxide was selected as electrode material of lead-acid batteries. In the present work, the performances of PbO₂/PbSO₄ or PbSO₄/Pb electrode transformed from PbCO₃ have been investigated by powder microelectrode technique combined with cyclic voltammetry. The results show that the CV characteristics of either negative or positive electrode prepared from PbCO₃ is as good as that of both electrodes made from lead oxide produced by mill machine,when a powder microelectrode with PbCO₃ transformed into PbSO 4 …

The Electrochemical Behaviors Of Superoxide Dismutase At Promoter Modified Gold Electrode, Xia-Qin Wu, Xiao-Yun Meng, Zhe-Su Wang, Zong-Rang Zhang

Journal of Electrochemistry

The electron-transfer process of superoxide dismutase was investigated by cyclic voltammetry at the 4,4'-dithiodipyridine, L-cysteine, histidine and arginine modified gold wire electrodes repectively. The quasi-reversible behavior was observed at L-cysteine modified gold electrode. An irreversible electrochemical behavior has been observed at hisdinine modified gold wire electrode.

Electro-Oxidation Of Phenol On Sno2/Ti Electrodes Prepared By Thermal Oxidation, Qing-Song Zhang, Hui-Huang Wu

Journal of Electrochemistry

A SnO₂/Ti electrode prepared by thermal oxidation was used as the anode for galvanostatic electrolysis in acidic solution containing phenol, the time-dependances of phenol concentration, chemical oxygen demand in solution(COD) and instantaneous current efficiency were determined during electrolysis. The results show that with the SnO₂/Ti anode instead of Pt, the COD significantly decreases at the same charge passage, and average current efficiency of oxidation increases by three times. The mechanism for phenol oxidation at two electrodes was discussed.

Evaluation Of The Transport Properties Of Gasb For Bipolar Applications Through Monte Carlo Simulations, Damayanthi Palaniappan

Electrical & Computer Engineering Theses & Dissertations

GaAs is currently the semiconductor material of choice for high speed, low power applications. Its electronic transport properties are superior to almost all other semiconductors. It is also used in a variety of bipolar applications such as photodetectors and photo-mixers. However, as is well known, the hole mobility and related transport parameters of GaAs are not very good. This is a serious drawback, and poses a potential problem for all applications involving bipolar conductivity. In order to increase the high :frequency limits and high-speed capability of bipolar devices, the choice of an alternative material, therefore, becomes necessary. An important first …

Structural And Electrochemical Studies On Lithium Manganese Oxide Containing Li+ Prepared By Hydrothermal Method For Lithium Ion Batteries, De-Yao Liu, Jin-Kua You, Wei Chu, Yong Yang, Zu-Geng Lin

Journal of Electrochemistry

In this paper, Todorokite manganese oxides containing Li⁺ with large tunnel structure (sample M5) have been synthesized by hydrothermal methods from natural manganese oxide nano fiber (sample M4). The structure and composition of the samples were characterized and analyzed by XRD, ICP, TGA and DTA. Its electrochemical behavior as a cathode materials for rechargeable lithium ion insertion were studied by galvanostatic charge/discharge measurements. XRD results show that the sample M4 is mainly composed of Birnessite and Vernadite structure. Although the sample M4 shows a high initial capacity of approximately 150 mAh/g, its performances decrease gradually over 30 cycles. It …

Deactivation Of Nickel Oxide/Hydroxide To Electrooxidation Of H2Po2 Anions On Nickel Electrodes In Alkaline Solutions, Tai-Xiang Jiang, Hui-Huang Wu

Journal of Electrochemistry

Electrooxidation of hypophosphite anions on polycrystalline nickel in alkaline solutions has been investigated by cyclic voltammetry and open circuit potential measurements. The results are explained based on the mechanism that the first step of hypophosphite oxidation is the adsorption of hypophosphite ions on nickel, followed by the homolysis of its hydrogen bond with the formation of radicals. The oxidation of hypophosphite on nickel in alkaline medium occurs at lower potentials between ca. -0.8 V— -1.1 V (SCE) and phosphite ion is the only oxidation product. There is no indication of hypophosphite oxidation at higher potentials. Severe deactivation of the surface …

The Techniques Of The Paired Electrosynthesis, Hong-Kun Zhang, Deng-Ping Gu

Journal of Electrochemistry

In this Paper, we introduce our work on paired electrosynthesis. In conjunction with our research practice, we introduce electrolytic conditions,such as material of electrode ,courrent density and electrolytic temperature etc,as reference for researcher. We categorize the paired electrosynthesis techniques to widen our view on the paired electroorganic synthesis and to promote the deveopments of paired electrosynthesis techniques.

Study On Synthesizing Of 2-Methylbutanoic Acid By Indirect Electrooxidation, Chong-Tao Zhao, Ze-Shan Zhu

Journal of Electrochemistry

The working conditions of synthesizing 2-methylbutanoic acid by oxidizing 2-methyl-1-butanol with tetrabutylammonium hydrosulfate (TBAS) or tetrabutylammonium perchlorate (TBAP) as phase transfer catalyst in sulfuric acid Cr(Ⅵ) oxidation medium was studied. The Cr(Ⅵ) oxidation medium could be electrolytic regenerated from Cr(Ⅲ), during above oxidation reaction. Under the optinum condition, the yield of 2-methylbutanoic acid is more than 95%.

The Ac-Impedance Analysis For Pluse Oxide Film Of Aluminium Alloy, Ai-Ling Du, Xi-Cheng Ma, He-Ming Zhang

Journal of Electrochemistry

Bode diagrams for aluminum PC (abbreviated from pulse current) oxide films were first obtained by AC-impedance measurements in a wide range of frequency. The experimental results show that different kinds of electrical equivalent circuits can be used for representing PC films and DC (abbreviated from direct current) oxide films separately, the main differences between them are their porous layers, the PC films are more even with little defects.Those are also verified by SEM and V-I characteristic curve measurements.

Electrochemical Synthesis Of Fes Electrode And Its Behavior Measurement, Cong-Sheng Guan

Journal of Electrochemistry

The Potential for the electrochemical synthesis of FeS electrode has been obtained by cyclic voltammetry. FeS electrodes were synthesiaed by controlling Fe electrode at -1.0 V in LiCl-KCl-Li₂S and Li(FClI)-Li₂S melts and their behavior were measured also. The FeS electrode synthesized in molten Li(FClI)-Li₂S has the best charge and discharge properties.

Investigation Of Solution Chemistry In Crevice Of Carbon Steel And Its Anodic Polarization Behavior, Zhuo Chen, Cui-Wei Du, Bei Cao, Yin-Shun Wu, Hai Yang, Zheng-Rong Zhang

Journal of Electrochemistry

A self-made wedge-shaped simulated crevice apparatus was designed to investigate the solution chemistry in crevice of carbon steel and its anodic polarization behavior. For carbon steel with 3.5%(wt) NaCl, the change and the distribution of electrode potential, concentration of Cl^- and pH value of solution in the crevice, and the current density of metal in the crevice were measured respectively under various conditions of anodic polarization. The results showed that without polarization the metal about 2 cm away from the opening of the crevice was attacked preferentially because of its lowest free corrosion potential. The anodic polarization promoted the …

The Behaviors Of Capacity Loss Of Limn2O4 Cathodeat Elevated Temperatures, Xiao-Hong Hu, Han-Xi Yang, Xin-Ping Ai, Sheng-Xian Li, Xin-Lin Hong

Journal of Electrochemistry

The capacity loss of spinel LiMn₂O₄ cathode at elevated temperatures was evaluated by constant current charge-discharge methods and it was found that serious capacity loss and cycleability decrease occured at above 50, especially for the charged cells. The mechanisms for this phenomena were examined by atomic emission and infrared spectrometry of the electrolyte, XRD measurment of the cycled elecrode and microelectrode voltammetry of LiMn₂O₄ at room and elevated temperatures. The results showed that with increasing temperature, Mn and Li ions tended to redistribute partly in the spinel framework due to the disproportion of Mn …

Electrochemical Behavior Of Riboflavin On Glassy Carbon Electrode, Hong Li, Lin-Cai Jiang, Liang-Nian Ji

Journal of Electrochemistry

The electrochemical behavior of riboflavin(RF) on glassy carbon has been investigated by using potential sweep, rotating ring-disc electrode and the measurement of differential capacitance. It is shown that a single well-behaved oxidation-reduction wave corresponding to a reversible two-electrons reaction apears in medium of pH<6, and the adsorption of RFH₂ formed by electro-reduction is weak and hence its solubility is good. In medium of pH>6, there are two separating but overlapping partly oxidation-reduction waves corresponding to two-step one-electron reaction. The adsorptions of RFH and RFH₂ produced by reduction reactions in medium of 6

Oxidation And Adsorption Of Deoxyribonucleic Acid At Highly Ordered Pyrolytic Graphite And Glass Carbon Electrode, Jian-Zhang Zhou, Ling-Ling Wu, Jin Luo, Zhong-Hua Lin

Journal of Electrochemistry

It is shown that calf thymus DNA (CT DNA) can be adsorbed at highly ordered pyrolytic graphite (HOPG) electrode and detected by differential pulse voltammetry (DPV) and electrochemical atomic force microscopy (ECAFM). It is found that controlled potential pre-polarization influences largely the adsorption of dsDNA while it has little influence on ssDNA. It is demonstrated that ECAFM is useful to exploit adsorption of DNA at HOPGE. The pattern of adsorption of DNA at HOPG electrode that fits best with the experimental data is proposed. The results aslo shows that UV/Vis reflection spectroscopy, which has not been used in studying electrochemical …

In Situ Ftir Spectroelectrochemical Study Of Palladium Hexacyanoferrate Thin Film Deposited On Glassy Carbon Electrode, Ai-Li Bo, Xiang-Qin Lin

Journal of Electrochemistry

The electrochemically deposited Palladium hexacyanoferrate thin film on Glassy Carbon electrode (PdHCF|GC) has been studied in HCl, KCl and NaCl solutions by in-situ external reflection FTIR spectroelectrochemical technique. It is found that the behavior of the electroactive PdHCF film can be understood in terms of two states: Pd₂Fe(II)(CN)₆ formed in the inner layer and (M⁺)2Fe(II)(CN)₆ (M⁺: electrolyte cation) formed in the outer layer. The inner layer is oxidized at E_m=0.87 V in 1 mol/L KCl, while for the outer layer Em=0.77 V(vs. Ag/AgCl). In 1 mol/L NaCl or HCl solutions, …

Influence Of Ptfe And Nafion On The Utilization Efficiency Of Pt/C Catalyst In Pemfc, Xiao-Liang Cheng, Bao-Lian Yi, Jing-Xin Zhang, Ming Han, Ya-Guang Qiao

Journal of Electrochemistry

With cycling voltammetry curve(C-V), TEM and SEM photographs, the influence of PTFE and Nafion on the platinum utilization in catalyst layer of PEMFC was investigated. The results show that in gas diffusion electrode, the blocking effect of PTFE in the platinum utilization is not pronunced. In the thin-film catalyst layer, the electron conduct of the catalyst was blocked by the nafion solid and this caused the decrease of platinum utilization. With the increase of the nafion content in the catalyst layer, both platinum utilization and the electron conductivity decreased in the catalyst layer. Because the molecule size of nafion is …

Preparation And Application Of Gold-Film On The Surface Of Bacterial-Modified Carbon Paste Electrode, Rong-Zong Hu, Yan-Ping Ruan, Hao Xu, Jin-Kun Fu, Wei-De Zhang, Wen-Yun Hu

Journal of Electrochemistry

A novel method for preparation of gold-film composed of ultra-fine gold particles was reported in this paper. The gold-film was prepared by electrochemical method on the surface of the paste electrode modified with the strain Bacillus sp. D01 which has strong ability to absorb and reduce Au³⁺. In addition, this paper reported an experimental method of determining trace amount of Cu²⁺ in water solution using cathodic stripping analysis to estimate the performances of the obtained gold-film. The experimental results indicated that this new method for preparation of gold-film is simple. The obtained gold-film electrode is stable and …

Low-Temperature Molecular Beam Epitaxy Of Gaas: A Theoretical Investigation Of Antisite Incorporation And Reflection High-Energy Diffraction Oscillations, K. Natarajan, Rama Venkat, Donald L. Dorsey

Electrical & Computer Engineering Faculty Research

Surface dynamics dominate the incorporation of charged, As+Ga, and neutral, As0Ga, antisite arsenic, and the temporal variation of reflection high-energy electron diffraction(RHEED) intensity in the low-temperature molecular beam epitaxy of (100) gallium arsenide(GaAs). A rate equation model is proposed which includes the presence and dynamics of a physisorbed arsenic (PA) layer riding the growth surface. The PA layer dictates the incorporation and concentration of As+Ga and As0Ga. Additionally, it influences the RHEED oscillations (ROs) behavior and the RO’s dependence on its coverage through its contribution to the reflected intensity. The model results for the dependence of As+Ga and As0Ga concentrations …

Output Control Of Vertical Microcavity Light Emitting Device, James A. Lott

AFIT Patents

An improved intracavity sensor based output power control for microcavity light emitting devices. An improved phototransistor transducer is both configured and physically disposed so that it passively transmits the spurious optical energy output of the microcavity light emitting device while simultaneously generating a light determined electrical signal of easily used large magnitude that is nearly free of error. The base-collector region of the transistor is disposed with a quantum well absorbing layer and produces a signal responsive to a selected emission wavelength. The configuration of the optical energy communicating transducer is arranged so that it is improved in sensitivity and …

Cracking In Cycloaliphatic Epoxy/Aluminum Composite Electrical Bushings, Keith Alan Parker

Doctoral Dissertations

The problem of cracking in electrical apparatus bushings as a result of thermal stresses was investigated. The bushings were composed of cycloaliphatic epoxy insulators with embedded aluminum conductors. The problem is due to the difference in coefficients of thermal expansion of the two materials. A solution to the problem had been to coat the conductors before they were formed together with the epoxy insulators. The coating was assumed to prevent cracking by allowing movement between the two materials as their dimensions changed during thermal expansion and contraction. The contribution of the coating was to be established.

The hypothesis was that …

Preparation And Surface Studies Of Negative Electron Affinity Semiconductors Photocathodes, Khaled A. Elamrawi

Electrical & Computer Engineering Theses & Dissertations

Fabrication of high quantum efficiency, long lifetime negative electron affinity photocathodes is important for applications such as photomultipliers, image intensifiers, electron beam lithography, electron microscopy, and polarized electron sources. The surface cleanliness of the III-V semiconductor photocathode is crucial in obtaining high photosensitivity.

GaAs(100) and InP(100) photocathodes are prepared by atomic hydrogen cleaning. The cleaning effect on the photocathode performance is discussed. The surface degradation mechanisms which reduce the photocathode lifetime are presented. The photocathode surface cleanliness, structure, and morphology are studied using reflection high-energy electron diffraction (RHEED).

Quantum efficiencies of ∼14% and 8% are obtained for GaAs and InP, …

A New Cell Structure For Proton Exchange Membrane Fuel Cell, Ming Han, Hong-Feng Xu, Bao-Lian Yi

Journal of Electrochemistry

Separating the functions of current collection and gas flow distribution and then to design two separate elements to achieve the desired performance characteristics, a nonconventional cell structure for proton exchange membrane fuel cells bave been developed. The current collector is achieved using a thin stain steel sheet, the gas flow distribution is achieved using a carbon paper that has the desired chemical durabiliy when in contact with the proton exchange membrane. Combining these two separate elements into a single divice yields a bifunctional device that performs as a bipolar separator plate. The advantages of this alternative appproach to making biplar …

Kinetic Study Of Electrooxidation Of Benzene, Xin-Sheng Zhang, Ping Ding, Ying-Chun Dai, Wei-Kang Yuan

Journal of Electrochemistry

A reaction kinetic study for electrochemical oxidation of benzene was performed on a PbO₂ rotating disk electrode in 1 mol/L H₂SO₄ aqueous solution. The reaction orders, the activation energies and transfer coefficient were measured, and the kinetic expression was obtained.

Oxidation Mechanism Of Hypophosphite, Dong-Bai Sun, Ying Jin, Hong-Ying Yu, De-Jun Yang

Journal of Electrochemistry

There exist two oxidation current peaks on the anodic polarization curve between -0.7 V and 0 V (SCE) in Na-hypophosphite solution. Peak Ⅰ (-0.55 V, SCE) , which represents the oxidation process from H₂PO₂^- to H₂PO₃^-, has been studied previously. Peak Ⅱ, which is located at the potential about -0.4 V (SCE), is investigated emphatically in this paper. The results show that, peak Ⅰ and Ⅱ are corresponding to two successive steps in oxidation process of H₂PO₂^-, i.e. peak Ⅱ corresponds to the oxidation process of …

Synthesis And Application Of Polymeric Corrosion Inhibitor For Reinforced Concrete, Wei-Wei Lin, Sheng-Xian Wang, Jian-Qing Zhang, Jun Yuan, Zhen-Guo Ji

Journal of Electrochemistry

A new polymer E-T was synthesized and used as a corrosion inhibitor for reinforced concrete. The inhibitive behavior and mechanism were studied with linear polarization, Tafel polarization, EIS and XPS method in simulated pore solution system with concrete samples. The result showed that the polymer was a mixing type inhibitor. A 1% dosage was sufficient to imhibit the corrosion of steel in simulated pore solution system. The salt endurance was enhanced from 0.02 mol/L to 0.10 mol/L. The result also showed the good synergetic effect of NaNO₂, especially in low NaNO₂ concentration. The EIS showed that E-T …