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Articles 91 - 112 of 112

Full-Text Articles in Computational Chemistry

Dynamic Simulation Of Oxygen Reduction Reaction In Pt/C Electrode For Proton Exchange Membrane Fuel Cells, Shang Li, Fen Zhou, Lei Chen, Mu Pan Apr 2016

Dynamic Simulation Of Oxygen Reduction Reaction In Pt/C Electrode For Proton Exchange Membrane Fuel Cells, Shang Li, Fen Zhou, Lei Chen, Mu Pan

Journal of Electrochemistry

It is an urgent need to reduce the Pt loading in electrode for practical fuel cell applications worldwide. Herein, we theoretically investigate the oxygen distribution, generated current, and minimum Pt loading of Pt/C electrode for practical applications based on kinetic model of oxygen reduction reaction. The results indicate that with increasing electrode effective thickness to 40 mm, serious concentration polarization is expected for Pt/C electrode. To generate a power density of 1.4 W⋅cm-2 (2.1A⋅cm-2@0.67 V) for fuel cell, the cathode catalyst layer thickness in PEMFC should be as thin as 3 mm. The minimum Pt loading will …

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Electrochemical Catalysis: A Dft Study, Li Li, Zi-Dong Wei Aug 2014

Electrochemical Catalysis: A Dft Study, Li Li, Zi-Dong Wei

Journal of Electrochemistry

In this review, we focus on achievements in electro-catalysis based on the density function theory study. The relationships among the electrode potential, electronic structure of catalysts and electro-catalytic activity are summarized in three parts: the adsorption and desorption of species, electron transfer, and stability of catalysts. The electrode potential and the electronic structure (d-band center or Fermi (HOMO) energy) of catalysts significantly influence the formation, adsorption and desorption of surface species on electrode. The electro-catalytic activity can be improved by modulating the electrode potential and electronic structure of catalysts.

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Effects Of Oxygen Coverage And Hydrated Proton Model On The Dft Calculation Of Oxygen Reduction Pathways On The Pt(111) Surface, Li-Hui Ou, Sheng-Li Chen Jun 2014

Effects Of Oxygen Coverage And Hydrated Proton Model On The Dft Calculation Of Oxygen Reduction Pathways On The Pt(111) Surface, Li-Hui Ou, Sheng-Li Chen

Journal of Electrochemistry

DFT calculation is used to study various possible steps in the oxygen reduction reaction (ORR), including the adsorption and dissociation process of O2 and the serial protonation process of dissociated products to form H2O on the Pt(111) surface. By using slabs of different sizes, and different numbers of pre-adsorbed oxygen atoms, the coverage effects on the pathways are investigated. The calculated results using different hydrated proton models are also compared. It is shown that the initial step of the ORR is the formation of a protonated end-on chemisorbed state of OOH*, which can transform to an unprotonated …

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A Dft Calculation Screening Of Pt-Based Bimetallic Catalysts For Oxygen Reduction, Li-Hui Ou, Sheng-Li Chen Feb 2013

A Dft Calculation Screening Of Pt-Based Bimetallic Catalysts For Oxygen Reduction, Li-Hui Ou, Sheng-Li Chen

Journal of Electrochemistry

Developing Pt-lean catalysts for oxygen reduction reaction (ORR) is the key for large-scale application of proton exchange membrane fuel cell (PEMFC). In this paper, we have proposed a multiple-descriptor strategy for screening efficient and durable ORR alloy catalysts of low Pt content. We argue that an ideal Pt-based bimetallic alloy catalyst for ORR should possess simultaneously negative alloy formation energy, negative surface segregation energy of Pt and a lower oxygen binding ability than pure Pt. By performing detailed DFT calculations on the thermodynamics, surface chemistry and electronic properties of various Pt-M alloys (M refers to non-precious transition metals in the …

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Application Of First Principles Calculations In Anode Materials For Lithium Ion Batteries, Tian-Ran Zhang, Dai-Xin Li, Si-Qi Yang, Zhan-Liang Tao, Jun Chen Jun 2012

Application Of First Principles Calculations In Anode Materials For Lithium Ion Batteries, Tian-Ran Zhang, Dai-Xin Li, Si-Qi Yang, Zhan-Liang Tao, Jun Chen

Journal of Electrochemistry

First principles calculations play an important role in the study and development of new materials for lithium batteries. In this paper, we review the application of first principles calculations in the design of anode materials, including the modeling of the interaction of lithium in the anode materials, capacity, voltage, electrochemical reaction process, diffusion, rate capability, the relationship between the structure and properties, and the experimental phenomena interpreting. Based on the discussions, we emphasize on the importance of first principles calculations and demonstrate their requirement for further development.

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Cloning And Characterization Of Sas0754, A Hypothetical Protein From Community Associated Staphylococcus Aureus, Unknown Unknown May 2012

Cloning And Characterization Of Sas0754, A Hypothetical Protein From Community Associated Staphylococcus Aureus, Unknown Unknown

Symposium 2012

Community associated Staphylococcus aureus (strain MSSA476) is a gram positive cocci capable of infecting many different parts of the body and known to cause serious infections that can be fatal, such as bacterial arthritis and acute endocarditis. To find effective ways of fighting against CA-MRSA strains we must learn more about their ability to infect. The focus of this study was cloning and characterization of a protein referred to as SAS0754. The size of SAS0754 is 340 amino acids and the gene sequence is 1023 nucleotides. The hypothetical function of this protein is that it is an extracellular matrix binding …

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A Convenient Synthesis Of 2,6-Dichlorohomonicotinic Acid, Chase Buchanan, Richard W. Fitch May 2012

A Convenient Synthesis Of 2,6-Dichlorohomonicotinic Acid, Chase Buchanan, Richard W. Fitch

Symposium 2012

In our synthetic efforts toward the alkaloid phantasmidine, we required a convenient source of the title compound. Herein, we describe a short synthesis of 2,6-dichlorohomonicotinic acid by direct allylation of 2,6-dichloropyridine with LDA/allyl chloride, followed by permanganate oxidation of the side chain [figure1]. Yields for the allylation are high, while permanganate oxidation required more adjustment. Successful conditions require the modest acidification of the mixture with acetic acid and cleanup by acid base workup. No chromatography is needed.

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Convenient Parallel Synthesis Of Alkyl- And Aryl-S-Tert-Butyl Thiothers, Rebecca Norcross, Jessica Stanfield, Richard W. Fitch May 2012

Convenient Parallel Synthesis Of Alkyl- And Aryl-S-Tert-Butyl Thiothers, Rebecca Norcross, Jessica Stanfield, Richard W. Fitch

Symposium 2012

While preparing novel cysteine derivatives as oxidation catalysts, we needed S-tert-butylcysteine. We also examined acid-promoted tert-butylation of thiols using tert-butanol as reagent and solvent. While cysteine and aminoethanethiol work well using tBuOH in 4M HCl, other thiols fail in the aqueous environment and aerobic conditions. We examined a variety of aliphatic and aromatic thiols in tBuOH with H2SO4 catalysis and found that argon sparging and the use of 1 eq of acid led to good yields in a parallel format.

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Dft Study Of Co2 Reduction To Hydrocarbons On Cu Surfaces, Li-Hui Ou, Sheng-Li Chen May 2011

Dft Study Of Co2 Reduction To Hydrocarbons On Cu Surfaces, Li-Hui Ou, Sheng-Li Chen

Journal of Electrochemistry

CO2 reduction on Cu(111) single crystal surfaces was studied using DFT calculations on the reaction energies and the minimum energy paths. The results indicated that the possible reaction paths for CO2 reduction on Cu(111) surface are CO2(g) + H* → COOH* → (CO +OH)*, (CO + H)* → CHO*, CHO + H → CH2O* → (CH2+O)*, CH2* + 2H* → CH4 or 2CH2* → C2H4. On Cu(111) surface, the reaction rate is controlled by steps of CH2O* → (CH2 …

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Initial Stage Of Atmospheric Corrosion Of Ndfeb(M35) In A Simulated Marine Atmosphere, Chun-Ling Li, Yuan-Tai Ma, Ying Li, Fu-Hui Wang Nov 2010

Initial Stage Of Atmospheric Corrosion Of Ndfeb(M35) In A Simulated Marine Atmosphere, Chun-Ling Li, Yuan-Tai Ma, Ying Li, Fu-Hui Wang

Journal of Electrochemistry

This study detailed the atmospheric corrosion behaviour of sintered NdFeB(M35) in a simulated marine atmosphere with 80% relative humidity(RH).The dissolution and subsequent reaction of NaCl particles cause the attack of NdFeB.The corrosion presented three representative types:if the electrolyte covered magnetic phase and Nd-rich phase,the Nd-rich phase was corroded firstly due to galvanic effect;if the electrolyte covered magnetic phase,magnetic phase was corroded along the grain boundary;if the electrolyte located near the position of defects,corrosion progressed along with the defect because of low concentration of oxygen inside the defect.With corrosion progressing,local corrosion areas were mutually connected,with Nd-rich phase and grain boundary being …

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The Accelerated Test Of Simulated Atmospheric Corrosion And The Rust Evolution Of Low Carbon Steel, Jun-Hua Dong, Wei Ke May 2009

The Accelerated Test Of Simulated Atmospheric Corrosion And The Rust Evolution Of Low Carbon Steel, Jun-Hua Dong, Wei Ke

Journal of Electrochemistry

It has been set up an accelerated method of simulating to atmospheric corrosion by using wet/dry alternate test.The rust evolution rule of mass change vs time(in logarithmic coordinate) of low carbon steel under this test shows two linear sections with different slopes,in which the rust evolution transition in weight change corresponds to the compactness transition and crystallization transition during the rust layer growth.It has found that the rust evolution rule of low carbon steel in Wanning exposure site correlates to the rust evolution rule obtained by simulating the coastal atmospheric corrosion test,and the rust evolution rule of low carbon steel …

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Corrosion Electrochemical Behavior Of Az31 And Az61 Magnesium Alloys In Simulated Sea Water, Ling-Jie Li, Sheng-Hai Yu, Jing-Lei Lei, Chuan-Pu Liu, Sheng-Tao Zhang, Fu-Sheng Pan Feb 2008

Corrosion Electrochemical Behavior Of Az31 And Az61 Magnesium Alloys In Simulated Sea Water, Ling-Jie Li, Sheng-Hai Yu, Jing-Lei Lei, Chuan-Pu Liu, Sheng-Tao Zhang, Fu-Sheng Pan

Journal of Electrochemistry

Tafel polarization curves and electrochemical impedance spectroscopy(EIS) techniques were employed to investigate the corrosion electrochemical behavior of AZ31 and AZ61 magnesium alloys.Scanning electron microscopy(SEM) was used to observe the alloy microstructure and corrosion morphology.The variation of the bulk corrosive medium pH with immersion time was recorded during the exposure of the alloys to simulated sea water.Results show that AZ61 magnesium alloy exhibits much better anti-corrosion ability than AZ31 magnesium alloy.The different corrosion behavior between the two magnesium alloys is correlated with their different content of Al alloying element.The higher content of Al in AZ61 alloy leads to the homogenerous microstructure …

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Study On The Electrochemical Impedance Spectroscopy (Eis) Of Al-Bronze At Different Anodic Potentials, Hui Yu, Sa-Ying Dong, Hai-Bo Xu, Ming-Xian Sun Feb 2004

Study On The Electrochemical Impedance Spectroscopy (Eis) Of Al-Bronze At Different Anodic Potentials, Hui Yu, Sa-Ying Dong, Hai-Bo Xu, Ming-Xian Sun

Journal of Electrochemistry

The corrosion dissolution mechanism of Al-bronze has been investigated by Electrochemical Impedance Spectroscopy (EIS) at different anodic potentials. In the active region, the corrosion products are complex compounds of cupreous chloride and the diffusion of CuCl2- is the control process of electrochemical reaction. In the transition region, there exhibits two capacitance loops on EIS because CuCl and cupreous oxides films deposit on the electrode surface. In the limiting current region, an inductance loop appears on the EIS because the breakdown of the oxides film leads to serious pit corrosion.

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Corrosion Behavior Of Reinforcing Steel In Concrete Subjected To Chloride Contamination By Eis, Rong-Gang Hu, Rong-Gui Du, Chang-Jian Lin May 2003

Corrosion Behavior Of Reinforcing Steel In Concrete Subjected To Chloride Contamination By Eis, Rong-Gang Hu, Rong-Gui Du, Chang-Jian Lin

Journal of Electrochemistry

Electrochemical impedance spectroscopy(EIS) was employed to study the influence of chloride on the corrosion behavior of reinforcing steel in concrete. In Nyquist plot, the spectrum consists of two semicircles, indicating that the reinforced concrete system contained two time constants,one derived from electrical double layer of reinforcing steel and the other from the deposition film of concrete layer. The depressed semicircle in lower frequency featured the non-faradic behavior of the electrical double layer (EDL) deviated from idea capacitor due to diffusive effect which was attributed to the surface roughness of rebar and the inhomogenity of concrete layer. Then the EDL was …

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Steady State Simulation Of Ysz Intermediate-Temperature Fuel Cell, Zi-Jing Lin, Ye Gu, Xiao-Hua Zhang Nov 2002

Steady State Simulation Of Ysz Intermediate-Temperature Fuel Cell, Zi-Jing Lin, Ye Gu, Xiao-Hua Zhang

Journal of Electrochemistry

With a coupled 2D electrochemical and thermal modeling software, the characteristics of the steady state operation of the intermediate-temperature fuel cell with thin yttria-stabilized zirconia(YSZ) electrolyte was analyzed. The parameters of I-V equation were obtained from fitting the experiment results and the choice of grid points was determined by balancing the accuracy requirement and computational efficiency. The temperature fields at different operation circumstances such as flow designs, material choices for interconnect, were examined. The dependences of the output power and cell efficiency on the operating voltage at different temperatures were studied. Based upon the analysis of the temperature profile, it …

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An Eis Study On The Synergetic Filming Between Cathodic Protection And The Corrosion Inhibitor, Yong-Tao Zhao, Jian-Hua Wu, Jian-Hua Qian, Hui Yu Feb 2000

An Eis Study On The Synergetic Filming Between Cathodic Protection And The Corrosion Inhibitor, Yong-Tao Zhao, Jian-Hua Wu, Jian-Hua Qian, Hui Yu

Journal of Electrochemistry

The electrochemical impedance spectroscope (EIS) of 907A steel in seawater was investigated to study the film formation and destruction. The corrosion protection mechanism of the synergy interaction between cathodic protection and YKI-5 corrosion inhibitor (a mixture of polyhydric alcohol phosphate ester, phosphate and polyphosphate) is discused. Typical EIS spectral changes were clearly observed during the film formation and destruction processes. EIS results indicated that the film seemed to formed a multi-layered structure which consist of an inner layer (this may be an inhibitor-metal complex layer) and many outer layers of calcareous deposits. The film possesses of good persistency under the …

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Direct Electrolysis Of Seawater On Conducting Film For Microbial Anticorrosion 1. Simulation And Measurement Technique, Wei-Ling Hu, Ling-Ling Wu, Jing Zhou, Jing-Xin Li, Jin Luo, Zhong-Hua Lin Aug 1999

Direct Electrolysis Of Seawater On Conducting Film For Microbial Anticorrosion 1. Simulation And Measurement Technique, Wei-Ling Hu, Ling-Ling Wu, Jing Zhou, Jing-Xin Li, Jin Luo, Zhong-Hua Lin

Journal of Electrochemistry

Based on the electrochemical micro probe and the weak signal detection technique, simulated test and measurement system were set up by the use of four-electrode cell(including a micro electrode), bipotentiostat, lock-in amplifier and three-dimensional micro manipulating device. Based on the system, the micrometer scale concentration distribution of trace hypochlorite, which is produced by direct electrolysis of seawater on the conducting film for preventing microbial corrosion has been obtained for the first time. Both relationships between concentration of hypochlorite and its reduction current, which is termed an working curve, and between the reduction current of hypochlorite and measured time are reported.

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Effects Of Nickel Content And Simulated Heat Affected Zone Of 2205 Duplex Stainless Steel On Pitting Corrosion, Horng-Yih Liou, Ju-Tung Lee, Wen-Ta Tsai, Rong-Iuan Hsieh, Yeongtsuen Pan May 1999

Effects Of Nickel Content And Simulated Heat Affected Zone Of 2205 Duplex Stainless Steel On Pitting Corrosion, Horng-Yih Liou, Ju-Tung Lee, Wen-Ta Tsai, Rong-Iuan Hsieh, Yeongtsuen Pan

Journal of Electrochemistry

The effects of nickel content and Gleeble simulated heat affected zone (HAZ) of 2205 stainless steel on pitting corrosion were investigated in this paper. The results showed that nickel content, ranging from 4.5 wt% to 6.5 wt% in base metal, had only a minor effect on the electrochemical polarization curves, with all Enp's and Epp's falling in the rang of 1100~1200 mV. Comparing with the base metal, the simulated HAZ microstructure caused an increase in the anodic current density, a distinct decrease in both Enp and Epp , and a reduction in the passive …

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Study On Steel Corrosion In Simulated Biofilm Environment In Seawater, Qing-Fei Wang, Jing Sui, Run-Xi Su, De-Ying Kong, Shi-Zhe Song Feb 1999

Study On Steel Corrosion In Simulated Biofilm Environment In Seawater, Qing-Fei Wang, Jing Sui, Run-Xi Su, De-Ying Kong, Shi-Zhe Song

Journal of Electrochemistry

Biofilm is one of the main factors that influence metal corrosion in seawater environment. According to the structure and property of biofilm, a natural biopolymeric gel, calcium alginate(an extracellular biopolymer containing carboxylate functional groups) can deposite on metal surfaces to form films. Corrosion behavior of alloyed steel E2, 10CrMoAl and 18-8 stainless steel were studied in simulated biofilm environment by various electrochemical methods ,including measurements of the corrosion potential, polarization curves,galvanic current and electrochemical impedance. The results show that such an approach is informative to reveal “how” and “to what extent” biofilm can influence the metal corrosion process.

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Corrosion Behaviour Of Copper Covered With Ion Selective Phenolic Coatings By Eis, Zhoucheng Wang, Yingzhou Zhang, Shaomin Zhou Aug 1997

Corrosion Behaviour Of Copper Covered With Ion Selective Phenolic Coatings By Eis, Zhoucheng Wang, Yingzhou Zhang, Shaomin Zhou

Journal of Electrochemistry

Electrochemical impedance spectroscopy(EIS) technique was employed to study the corrosion behaviour of copper painted with the anion selective, cation selective and bipolar phenolic coatings in 3% NaCl solution. From the impedance spectrum characteristics, the models of equivalent circuit for these different coating systems were established, and the methods for the analysis of experimental impedance diagrams in terms of coating and interface properties were discussed. The research results show that the composition and structure of ion selective coatings have significant influence on corrosion behaviour of copper. The bipolar coating consisting of an anion selective inner layer and a cation selective outer …

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Growth Kinetics And Breakdown Of Passive Films On Rebar Electrodes In Simulated Cement Pore Solution, Wei Chu, Yuanxiang Shi, Baoming Wei, Yong Yang, Xuguang Chen, Zugeng Lin Nov 1995

Growth Kinetics And Breakdown Of Passive Films On Rebar Electrodes In Simulated Cement Pore Solution, Wei Chu, Yuanxiang Shi, Baoming Wei, Yong Yang, Xuguang Chen, Zugeng Lin

Journal of Electrochemistry

The growth kinetics and breakdown of passive films on REBAR electrodes insimulated cement solution (pH=12.5 and 13.8) have been investigated using in situ photoelectrochemical methods and potential step method. The results show that there are two mainstages in the growth of the film, with two rate functions characterized by linear relation between thefilm thickness and the direct logarithm of time. There is a sign in laser-scanning photoelectrochemical microscopic image just before the passive film breaks down. The addition of inhibitor NaNO2 changes the growth kinetics and thickness of the film, and therefore improves the resistance of pitting corrosion induced …

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The Photoelectrochemical Studies Of Passive Films On Rebar Electrodes In Simulated Cement Pore Solution, Wei Chu, Yuanxiang Shi, Baoming Wei, Yong Yang, Xuguang Chen, Zugeng Lin Aug 1995

The Photoelectrochemical Studies Of Passive Films On Rebar Electrodes In Simulated Cement Pore Solution, Wei Chu, Yuanxiang Shi, Baoming Wei, Yong Yang, Xuguang Chen, Zugeng Lin

Journal of Electrochemistry

The electronic properties of the passive film on REBAR electrodes in simulatedcement pore solution (pH=9.0～13.8) have been investigated using in-situ photoelectrochemical methods. The results show that the passive film is composed of mixed oxides of ferrum, and it is an amorphous, n-type semiconductive film. Variations of pH values, ions in the solution and film-formation potentials can affect the composition of the films. There are two main stages in the growthof the film, with two rate functions characterized by linear relation between the film thickness and thelogarithm of time. The addition of inhibitor NaNO2 changes the composition, structure and growth …

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