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In this work, the activity coefficients of sodium nitrate in the ternary system NaNO3–Cu(NO3)2–H2O were experimentally determined at 298.15 K in the range of total ionic strength I = 0.01 – 1.00 mo...

The present study reports a simple, inexpensive, and direct method for the preparation of nanocomposite (NC) material (Ni/Co-NC) as advanced catalysts for hydrogen production (HP). The Ni/Co-NC was prepared using solvothermal method (STM) followed by thermal annealing, characterized and tested for HP in 0.6 M H2SO4. The as-synthesized Ni/Co-NC contains a high density of active edge sites, exhibits high electro-catalytic HP activity under small cathodic onset potential (VON-P) of −0.03 V, and a small Tafel slope of approximately 29 mV/decade, which exceeds the activity of previously studied Pt-free catalysis. Annealing temperature significantly affects the Ni/Co-NC activity toward HP by forming active nanoparticles with an optimum identified at 250 °C. The HP process is controlled via Volmer-Tafel charge-transfer mechanism over the electrode interface. The presented method can be used as a new strategy for manufacturing advanced electro-catalysts for the production of hydrogen from different resources.

In this paper, the liquid-free battery Na-ISE | NaBr (m1), Na2SO4 (m2) |Br-ISE was used to measure the average activity coefficient of the ternary system NaBr–Na2SO4–H2O at 308.15 K by using the ce...

The iron–chromium (FeCr) redox flow battery (RFB) was among the first flow batteries to be investigated because of the low cost of the electrolyte and the 1.2 V cell potential. We report the effect...

In this article, research on the thermodynamic mean activity coefficients for the ternary system (NaCl–SrCl2–H2O) has been carried out. A cell without a liquid junction can be expressed as sodium–I...

Potentiometry is one of method on measuring metals based on cell potential. Measurements using potentiometry are divided into comparative cells and concentration cells. Concentration cells are measurements of a cell's potential by using two solutions with different concentrations. The aim of this study was to develop a concentration cell potentiometric method equipped with applications so measurements are easier and faster. The added application able to calculate the results of experiments so that the calculation process becomes faster and easier. Validation results give the results of the R the value of 0.9990; LoD 7.6484x10-7, LoQ 6.2103x10-7, RSD 0.64%, and recovery 98.05%. This optimum measurement was carried out at 30 oC and pH 5. The results of Cu measurements in well water obtained the result of 0.9633 ppm. Measurements using the development of this method, get good validation results and can be used on measurements similar to those in the aquatic environment. Keywords: Potentiometry, cell concentration, Copper (Cu), validation, aquatic environment

Chlorophenols have a strong medicinal smell and can be detected by the human nose at parts-per-million levels. Therefore, continuous monitoring of chlorophenols in water supplies is highly important. Herein, we reported a microfluidic sensor which can be used to detect 2,4-dichlorophenol (2,4-DCP) in real time with a limit of detection of around 0.1 ppm. The microfluidic sensor is a membrane-less galvanic cell which consists of two laminar flows running in parallel inside a straight channel. The sensor measures the potential difference between a solution containing 2,4-DCP and a reference solution containing acetate buffer. In a continuous-flow mode, the cell potential is proportional to the concentration of 2,4-DCP. To render specificity for the sensor, we incorporate a pre-treatment section where the incoming solution containing 2,4-DCP is split into two streams. One of the streams is brought into contact with cross-linked laccase aggregates (which catalyzes the hydrolysis of 2,4-DCP) and the second stream is taken as a reference solution. By comparing the potential difference between the two streams, we can determine the concentration of 2,4-DCP with high specificity. The microfluidic sensor platform is potentially useful for real-time detection of micropollutants present in aquatic systems with high sensitivity and specificity.

Potentiometric probes used in direct potentiometry are attractive sensing tools. They give information on ion activities, which is often uniquely useful. If, instead, concentrations are desired as sensor output, the ionic strength of the sample must be precisely known, which is often not possible. Here, for the first time, direct potentiometry can be made to report concentrations, rather than activities. It is demonstrated for the detection of monovalent anionic species by using a self-referencing Ag/AgI pulstrode as the reference element instead of a traditional reference electrode. This reference pulstrode releases a discrete quantity of iodide ions from the electrode and the resulting reference potential varies with the activity coefficient of iodide. The effects of activity coefficient on the indicator and reference electrode are therefore compensated and the observed cell potential may now be described in a Nernstian manner against anion concentration, rather than activity. Theoretical simulations and experimental results support the validity of this approach. For most monovalent anions of practical relevance, the potential difference between this approach and from a traditional activity coefficient calculation is less than 0.5 mV. The concept is validated with an all-solid-state nitrate sensor as well as a commercial fluoride-selective electrode, giving Nernstian responses in different ionic strength backgrounds against concentration without the need for correcting activity coefficients or liquid junction potentials.

The solvent 1,2-butylene carbonate (1,2-BC) displays a set of properties and a price comparable with that of propylene carbonate (PC). In this work we investigate the use of 1,2-BC in combination with the salt butyl-1-methylpyrrolidinium tetrafluoroborate (Pyr14BF4). We showed that the electrolyte 1.5 M Pyr14BF4 in BC displays good conductivities and viscosities, and that is use allows the realization of EDLCs with operative cell potential as high as 3.15 V. These high potential devices display good cycling stability at room temperature. At higher temperature their stability appears comparable of that of devices containing standard electrolytes.

Predicting the hydrate formation condition is an important issue for determining high CO 2 content natural gas transport. The widely used Parrish-Prausnitz (P-P) model cannot predict the hydrate formation temperatures and pressures accurately for high CO 2 content natural gas. This paper introduced a simple correction factor into the P-P model, resulting in an improved P-P model. The analytical expression of this new parameter is developed by correlating the deviations of the predicted hydrate formation temperatures with the CO 2 molar fraction in the gas mixtures. A total of 140 sets of experimental data were applied to validate the proposed model, which covered wide pressure and CO 2 molar fraction ranges of 1.45–13.0 MPa and 0–90%, respectively. The results show that the improved P-P model balances a simple form with high accuracy. The average deviation of the improved P-P model is 0.098 °C, whereas that of the original P-P model is 2.424 °C. It is essentially comparable in its prediction ability to CSMGem software and the cell potential method when it is applied to predicting the hydrate temperatures of high CO 2 content natural gases.

The cell potential of magnesium metal anode batteries is currently limited by the lack of stable and non-corrosive electrolytes. In a recent issue of Nature Chemistry, Son et al. demonstrated an artificial interphase on Mg anode that extends the electrolyte stability range while enabling magnesium transport. This approach paves the way for practical assessment of high-voltage cathodes and the assembly of high-energy-density Mg cells. Extension of the concept to other multivalent systems is also exciting.

Following the concepts illustrated within the previous chapter, an analogy is presented here between the working mechanisms of galvanic cells and biological redox reactions. These processes are explained here to underline the working principle of power conversion within biomass generation and to provide students with clear information on the reactions of oxidation and reduction and how they are coupled. The chapter underlines the necessity of interdisciplinary research, above all when the research is focused on renewable energy technology. As a matter of fact, and as was previously written, new trends in this field are related to artificial photosynthesis among others. In this chapter, the working principles of galvanic cells are explained in simple terms with emphasis on the electrochemical potential formation and the overall calculation of the cell potential in terms of half-cell reactions.

In this communication, effective cage radii of dodecahedral (D) cages in semiclathrate hydrates are investigated based on van der Waals and Platteeuw model. According to recent findings in semiclathrate hydrate structures, D cages in semiclathrate hydrates have anisotropic shapes which provide unique gas capacity and selectivity under mild temperature and pressure conditions. Since applications of these materials for cool energy storage and gas capture and storage technologies are expected, thermodynamic modeling of the semiclathrate hydrates is an emerging issue. So far, the van der Waals and Platteeuw model which is based on Langmuir adsorption theory has been used for modeling of canonical gas hydrates and semiclathrate hydrates. The model applies spherical cell potential to predict guest gas inclusion in the cages, and each cage is characterized by its radius with sphere approximation. While sizes of D cages in semiclathrate hydrates are quite similar to those in gas hydrates, their shapes are found to be irregularly anisotropic dodecahedra that can provide unique gas capture and storage properties. Therefore, when the van der Waals and Platteeuw model is applied to semiclathrate hydrates, it is necessary to discriminate the D cages in the model from those in canonical gas hydrates. Adjusting D cage radius in spherical cell potential model is a simple and convenient way to describe differences in cage shape between semiclathrate hydrates and canonical gas hydrates. Here, we investigated effective cage radii of D cages in the semiclathrate hydrates based on the conventional cell potential model with sphere approximation. Effective radii of D cages in the semiclathrate hydrates were found to be different from those in canonical gas hydrates. With the presently suggested radii, the conventional cell potential model can predict experimental data for cage occupancy in the semiclathrate hydrates more precisely.

A student-made galvanic cell is proposed for temperature measurements of cell potential. This cell can be easily constructed by students, the materials needed are readily available and nontoxic, and the solution applied is in an attractive color. For this cell, the potential values are excellently reproducible at each temperature, and the potential–temperature coefficient is well measurable. This experiment illustrates the determination of thermodynamic properties of a cell reaction, such as changes in entropy, enthalpy, and Gibbs energy through measurements of cell potential as a function of temperature. Students are led to understand the significance of those quantities. They also get to know the role of a supporting electrolyte in the electrochemical system.

To enhance the performance of an Ni-based cathode in a solid oxide electrolysis cell (SOEC) at medium temperature (600–800 °C), the present study adopted the method of adding Fe to Ni to fabricate Ni-Fe bimetal. Adding Fe can effectively inhibit Ni particles from becoming coarsen to enhance performance of Ni-based cathode. In the present study, the effects of different Fe contents in Ni1-xFex (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) bimetallic materials on the performance of the Ni-based cathode for SOECs were systematically studied, and the optimal Fe content for Ni-Fe bimetallic materials suitable for use as the cathode of a SOEC was ascertained. The optimal Fe molar content is 40%. Under the open circuit voltage, the SDC-Ni0.6Fe0.4 based SOEC has a lower polarization impedance than other SOECs. Besides, at the same cell potential, the SDC-Ni0.6Fe0.4 based SOEC has a higher current than other SOECs. Furthermore, the SDC-Ni0.6Fe0.4 based SOEC exhibits good stability. Accordingly, this study proved that Ni-Fe bimetal with an appropriate proportion can enhance the performance of Ni-based cathode, and it was also demonstrated that at medium temperature, this material acts as an excellent cathode for a SOEC.

Electrolyzer technologies have been gaining more attention, as they serve as a potential hydrogen production method that is capable of producing high-purity hydrogen from water and able to meet hydrogen demands at various capacities. In this contribution, water electrolysis technologies for hydrogen production are discussed in the context of different electrolysis processes, including the historical development, theoretical thermodynamic, and electrochemical principles. Electrode and electrolyte materials are reviewed for the various types of electrolyzers, and the current state-of-the-art applications and technologies are presented. Numerous illustrative examples are provided to cover critical concepts and provide deeper understanding. Alkaline, proton exchange membrane (PEM), and solid oxide electrolyzers are commercially available or at an advanced level of demonstration and in the foreseeable future are expected to be available in the market. The theoretical and technical background of each of these electrolyzers is presented and discussed. Additionally, the limitations of these electrolyzers are highlighted in the context of the research and development efforts of the scientific community to overcome these challenges. A case study is also presented to demonstrate how the thermodynamic and electrochemical models can be used to predict and evaluate the performance of a high temperature solid oxide electrolyzer where the cell potential, the different cell polarizations, and cell efficiencies are evaluated. The contribution includes a section on the environmental impact of electrolyzers under which the impact of electrolyzers on the environment is discussed and compared with other hydrogen production methods utilizing life cycle assessment as a comparative measure. Lastly, the economics of electrolyzers is discussed to compare the cost of hydrogen production using state-of-the-art electrolyzers with the cost of conventional technologies. The contribution concluds with remarks reflecting on the main concepts covered in this contribution along with future directions.

Taguchi experimental design with the alternating and direct current (AC and DC) electrocoagulation (EC) using initial fluoride concentration of contaminant, retention time, pH, electrode type, and voltage was used on fluoride removal. DC current is significantly more efficient than AC, and Al has a higher performance than Fe electrode (p

The purpose of this work is to develop a one-dimensional mathematical model for predicting the cell performance of a direct formic acid fuel cell and compare this with experimental results. The predicted model can be applied to direct formic acid fuel cells operated with different formic acid concentrations, temperatures, and with various electrolytes. Tafel kinetics at the electrodes, thermodynamic equations for formic acid solutions, and the mass-transport parameters of the reactants are used to predict the effective diffusion coefficients of the reactants (oxygen and formic acid) in the porous gas diffusion layers and the associated limiting current densities to ensure the accuracy of the model. This model allows us to estimate fuel cell polarization curves for a wide range of operating conditions. Furthermore, the model is validated with experimental results from operating at 1–5 M of formic acid feed at 30–80 °C, and with Nafion-117 and silane-crosslinked sulfonated poly(styrene-ethylene/butylene-styrene) (sSEBS) membrane electrolytes reinforced in porous polytetrafluoroethylene (PTFE). The cell potential and power densities of experimental outcomes in direct formic acid fuel cells can be adequately predicted using the developed model.

A metal-free and all-organic redox flow battery is proposed and investigated. It employs polythiophene microparticles dispersed in electrolyte solutions as the redox couple and does not depend on limited metal resources. It shows a high cell potential and stable charge/discharge performance with a high energy efficiency of 60.9%.

The chemical diffusion coefficients of lithium ions ( D Li ) in spherical Li[Ni 0.5 Mn 0.3 Co 0.2 ]O 2 are systematically determined by galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS). The D Li obtained from GITT are greatly dependent on the lithium content and cell potential. In the charge process, the D Li values are in the range of 9.0 × 10 −11 to 3.3 × 10 −9 cm 2 s −1 . In the discharge process, the D Li values are in the range of 1.9 × 10 −11 to 3.9 × 10 −9 cm 2 s −1 . In addition, the minimum values in the D Li are observed at the stoichiometry x ≈ 0.25 for Li 1− x [Ni 0.5 Mn 0.3 Co 0.2 ]O 2 , which coincide with the voltage-plateau region at about 3.75 V. The D Li obtained from EIS are in the range of 1.7 × 10 −11 to 6.5 × 10 −9 cm 2 s −1 and the variation tendency with cell potential is consistent with the results obtained from GITT during the charge process.

Bipolar membrane electrodialysis for the production of organic bases, in contrast to organic acids, has received little attention in the scientific literature. In the present work we have investigated and compared different membrane configurations for the alkalinization of monoethanolamine salts into the organic base monoethanolamine. A current utilization of only 36% has been obtained for a two compartment configuration with bipolar and anion-exchange membranes. Proton tunneling through the anion-exchange membrane has been identified as the main reason for this relatively low current utilization. Minimizing proton tunneling by employing proton blocking anion-exchange membranes and using a three compartment configuration, the current utilization could be increased to 80%. This bipolar membrane configuration acts as a concentration step as well. A MEA concentration of 32 wt% in the base compartment could be achieved. A disadvantage of the three compartment configuration is the relatively high unit cell potential drop of 3.1 V at a current density of 1000 A m−2 using a compartment thickness of 0.75 mm.

The proton exchange membrane fuel cell (PEMFC) cannot react 100% of fuel, because the cell potential becomes zero if all of the fuel is consumed in the PEMFC. Therefore, a small amount of fuel is always released from the PEMFC. The exhausted H2 should be treated for safety. The VCell–iave characteristics were measured while varying the hydrogen concentration from 99.99% to 1%. In addition the VCell of the constant voltage control was selected with reference to the measured VCell–Iave characteristics. It was found that low-concentration hydrogen could be treated at VCell = 0.15 to 0.3 V by the hydrogen pump and at VCell = 0.4 to 0.6 V by PEMFC. The exhaust hydrogen concentration was reduced to several tens of ppm. © 2011 Wiley Periodicals, Inc. Electron Comm Jpn, 94(3): 51–59, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10292

The application of polymers bearing tetracyano-9,10-anthraquinonedimethane (TCAQ) units as electrode materials in organic batteries enables one narrow charge discharge plateau due to the one two-electron-redox-reaction of the TCAQ core. Li-organic batteries manufactured with this polymer display repeatable charge–discharge characteristics associated with a capacity of 156 mA h g−1 and a material activity of 97%.

A two-dimensional, nonisothermal, transient model is developed which is capable of predicting polymer-electrolyte fuel-cell performance during cold start. Transport of water in gas, liquid, and membrane phases at temperatures both above and below 0°C is included. In the porous media, the saturation levels of ice and liquid, as well as their pressures, are predicted based on the chemical potential of each phase and the physical and chemical properties of the cell materials. Simulation results show that liquid-water transport near but below 0°C plays an important role in determining the cell potential as a function of time during startup because it can allow for rapid drainage of the cathode catalyst layer once enough fine-pore ice has melted.

In our previous paper, a new experimental technique based on the potentiometric method was developed to obtain thermodynamic activity data (in form of activity ratio) particularly for ternary electrolyte+nonelectrolyte+H 2 O solutions supersaturated with the nonelectrolyte. In this paper, a rigorous thermodynamic approach is proposed to derive activity data for binary nonelectrolyte+H 2 O solutions in the supersaturated region, via cell potentials of an electrolyte tracer and solubility data of the nonelectrolyte. An analysis of thermodynamic consistency is presented to evaluate the reliability and accuracy of the measured data. A systematic experimental investigation of three ternary electrolyte+nonelectrolyte+H 2 O and two binary nonelectrolyte+H 2 O systems is reported in both under-saturated and supersaturated regions (up to a supersaturation level of approximately 27%). Interesting thermodynamic behaviors are observed and their significance is discussed, with the role of thermodynamics in exploration of crystallization phenomena highlighted.

Proton exchange membrane fuel cell (PEMFC) can hardly react a hundred percent of fuel, because a cell potential becomes zero if all of the fuel is consumed at PEMFC. Therefore a small amount of fuel is always released from PEMFC. The exhausted H2 should be treated for safety. iave-Vcel characteristics were measured changing hydrogen concentration from 99.99% to 1%. Moreover, Vcell of the constant voltage control was selected from the measured Vcell-iave characteristics, the low concentration hydrogen could be treated under Vcell =0.15 - 0.3V by hydrogen pump and Vcell =0.4 - 0.6V by PEMFC. The exhaust hydrogen was reduced to the hydrogen concentration of several tens of ppm.

The redox properties of verdazyl radicals are presented using cyclic voltammetry techniques. These radicals can be reversibly reduced as well as oxidized. Electron-donating and -withdrawing substituents have significant effects on the oxidation and reduction potentials as well as the cell potential (E(cell) = | E(ox) degrees - E(red) degrees |) for these radicals; a correlation between the electron spin distribution and redox properties is developed.

A procedure to predict the state of charge of a lithium ion cell using experimental data (cell potential versus time), as it becomes available, is presented. The procedure is based on the physics of the system and provides a realistic estimate of the state of charge of the cell as a function of time, for a given set of properties of the electrodes. An electrochemical cell model is used to obtain an extended Kalman filter (EKF) for estimating the state of charge (SOC) of a lithium ion cell in which the negative electrode is the limiting electrode. The method could also be used for a cell in which the positive electrode is limiting. © 2006 Elsevier B.V. All rights reserved.

EMF of galvanic cell with zirconia –based solid electrolytes was measured to determine the activity of Ga in liquid Ga-Sb-Tl alloys between 946 and 1233 K along the tree pseudobinary lines of Ga-(Sb/Tl), (xSb/xTl = 1/3, 1/1 and 3/1) The cell used was: Ga,Ga2O3|(ZrO2)0.92(Y2O3) 0.08|Ga-Sb-Tl, Ga2O3. The activity of Ga (aGa ) was derived by :-3EF = RT ln aGa , where E is cell potential, F is Faraday’s constant, R is gas constant and T is cell temperature. The activity of Ga shows slight negative deviations from ideality in the section with positive deviation from ideality in the whole composition range. The activity of gallium shows slight negative deviations from Raoult’s law in the section with xSb/xTl = 3/1, moderately positive deviations in xSb/xTl =1/1 section and large positive deviations in xSb/xTl =1/3 section.

The Advanced Spent Conditioning Process (ACP) developed by the KAERI is based on pyrometallurgy and the electrolytic reduction plays a central role in transforming spent oxide fuels into metals. The constituents of the spent fuels are distributed between a salt and a reduced metal phase during electrolysis. Lithium metal is produced in a molten LiCl-Li2O cell and then it reacts with the metal oxides of the spent fuel producing Li2O and reduced metals. By focusing on the activity of Li2O and the electric potential, the electrolytic reduction process of the ACP is discussed. Thermodynamic considerations are defined and operation conditions are proposed including Li2O activity and cell potential.

M{sub 2}Mn{sub 3}O{sub 8} (M=Ca{sup 2+}, Cu{sup 2+}) compounds were synthesized and characterized in lithium cells. The M{sup 2+} cations, which reside in the van der Waal's gaps between adjacent sheets of Mn{sub 3}O{sub 8}{sup 4-}, may be replaced chemically (by ion-exchange) or electrochemically with Li. More than 7 Li{sup +}/Cu{sub 2}Mn{sub 3}O{sub 8} may be inserted electrochemically, with concomitant reduction of Cu{sup 2+} to Cu metal, but less Li can be inserted into Ca{sub 2}Mn{sub 3}O{sub 8}. In the case of Cu{sup 2+}, this process is partially reversible when the cell is charged above 3.5 V vs. Li, but intercalation of Cu{sup +} rather than Cu{sup 2+} and Li{sup +}/Cu{sup +} exchange occurs during the subsequent discharge. If the cell potential is kept below 3.4 V, the Li in excess of 4Li{sup +}/Cu{sub 2}Mn{sub 3}O{sub 8} can be cycled reversibly. The unusual mobility of +2 cations in a layered structure has important implications both for the design of cathodes for Li batteries and for new systems that could be based on M{sup 2+} intercalation compounds.

This paper presents a mathematical model based on a porous-electrode theory to describe the discharge of a lithium ion cell. The expression for the electrostatic cell potential has been obtained by subtracting the overpotential at the front of the anode from the overpotential at the back of the cathode plus the integral of the solution phase electrostatic potential in the cathode and the separator. The resulting expression is used to plot the cell potential against time and is compared with experimental results using parameter values from the literature.

Fluorotubes (C2F) were prepared by fluorinating SWNTs with F2/HF at 250 °C for 12 h and were consequently used as cathode material in a lithium electrochemical cell. The Raman and FTIR spectra of the fluorotubes were investigated before and after the cell was discharged. The discharging performance of the fluorotube/lithium electrochemical cell was studied and compared with that of a carbon monofluoride (CFx)/ lithium cell. Thermodynamic calculations using the ¢Hf° of fluorotubes and carbon monofluoride indicated that the potential of a fluorotube/ lithium electrochemical cell, where the fluorotubes were made by the fluorination of armchair (10,10) SWNTs, should be 0.4 V higher than that of a carbon monofluoride/lithium cell. The experimental results support the theoretical calculations. The relation between SWNT diameter and cell potential was also investigated.

This paper describes an effort in developing reference systems to be used in high temperature subcritical and supercritical aqueous solutions for assessing the viability and accuracy of high-temperature pH sensors. Each of these reference systems consists of a couple of three-component aqueous solutions in which the concentration of NaCl is greater than the concentration of another solute, such as HCl and NaOH. The viability of the reference systems was tested using the recently published experimental data employing a flow-through electrochemical cell at temperatures from 25°C to 400°C and densities from 0.17 to 1 g cm −3 [S.N. Lvov, X.Y. Zhou, and A.V. Bandura, 1999a, Estimation of Isothermal Potential for HCl/NaCl and NaOH/NaCl Systems in High Temperatures Supercritical Aqueous Solutions, J. Supercrit. Fluids, in preparation; S.N. Lvov, X.Y. Zhou, and D.D. Macdonald, 1999, Flow-Through Electrochemical Cell for Accurate pH Measurements at Temperature up to 400°C, J. Electroanal. Chem., 463, 146–156]. The applicability of the method was tested for dilute (0.01 and 0.001 mol kg −1 ) HCl aqueous solutions having background NaCl electrolyte in the amount of 0.1 mol kg −1 . The most significant property of the reference systems is that the pH difference, and hence, the cell potential, can easily be estimated with sufficient accuracy using only the analytical concentrations of the electrolytes without considering the speciation calculations, given the fact that the association and dissociation constants at supercritical temperatures have not been accurately determined yet.

A mathematical model for phosphoric acid fuel cell (PAFC) cathodes has been developed. The model, based on equations that take activation and diffusional problems into account, provides a description of the electrochemical behaviour of the electrode. These studies allow optimization of the morphological characteristics of this cell component and improvement in the performance of the whole fuel cell. In particular, the sensitivity analysis carried out on the model provides information on the influence of single parameters. Accordingly, the as optimized cathode allowed a performance of 700 mV at 200 mAcm−2 in air; the corresponding cell potential also increased from 500 mV at 150 mAcm−2 to 510mV at 200 mAcm−2.

The presence of two disulfide groups in the tetrathiophenalenyl radical TTPLY leads to a highly delocalized spin distribution and the lowest cell potential ever observed for a monofunctional phenalenyl derivative. While the heteroatom substituents successfully block C-C bond formation, TTPLY nonetheless associates in the solid state to afford the hypervalent S-S-bonded dimer (TTPLY)2.

The standard hydrogen electrode (SHE) acts as a primary reference in electrochemistry. The standard potentials of all other reference electrodes are linked to that of the SHE at the same temperature. The SHE contribution to the cell potential is by convention zero at all temperatures (see Chap. 1).

We present a reformulation of the Korringa - Kohn - Rostoker (KKR) coherent-potential approximation (CPA) which affords a number of conceptual and practical advantages over conventional formulations of the theory. In particular, as presented here the method can facilitate application to systems that cannot be described properly by a muffin-tin approximation to the cell potential and require a full potential treatment. Also, the formalism allows the derivation of the KKR CPA self-consistency condition within both a scattering matrix and a Green function approach, leading to uniquely defined species-resolved charge densities and densities of states. As shown in a companion paper, this formulation also allows the treatment of the so-called charge-transfer effects associated with Wigner - Seitz cells in an alloy which contain net amounts of charge.

A modified cell model is used for the solid-liquid phase transition in the low-pressure region for Lennard-Jones systems. Effects due to randomness of neighboring atomic positions are included in the cell potential. The free energy is then calculated after imposing self-consistent conditions on cell irregularity. Two minima are observed on the free energy versus cell dimension curves, leading to bifurcations into solid and liquid phases by double-tangent construction. The theoretical results in the low-pressure region are in good agreement with molecular dynamics results and also with the experimental data or argon.

We use simplified models based on porous-electrode theory to describe the discharge of rechargeable lithium batteries and derive analytic expressions for the cell potential, specific energy, and average power in terms of the relevant system parameters. The resulting theoretical expressions are useful for design and optimization purposes and also can be used as a tool for the identification of system limitations from experimental data. The system treated is an ohmically-limited cell with no concentration gradients having an insertion reaction whose open-circuit potential depends linearly on state-of-charge. Although the slope of the open-circuit potential controls the reaction distribution in the porous electrode, we find that the cell potential is independent of this slope. The results are applied to a cell of the form Li|polymer|LiyMn2O4 in order to illustrate their utility.

Two experimental techniques - equilibrium or reversible cell discharge and measurement of open circuit potential as a function of temperature - are used to determine the thermodynamic data needed to estimate the heat generation characteristics of Li/BCX and Li/SOCl2 cells. The results obtained showed that the reversible cell potential, the temperature dependence of the reversible cell potential, and the thermoneutral potential of the BCX cell were 3.74 V, -0.857 +/- 0.198 mV/K, and 3.994 +/- 0.0603 V, respectively. The respective values obtained for the Li/SOCl2 cell were 3.67 V, -0.776 +/- 0.255 mV/K, and 3.893 +/- 0.0776 V. The difference between the thermoneutral potential of Li/BCX and Li/SCl2 cells is attributable to the difference in their electroactive components.

The primary feedback control apparatus in the outer retina is the sign-inverting feedback synapse between horizontal cells and cones. In many lower vertebrates horizontal cells release GABA in darkness, which opens Cl- channels in cones. Input-output relations of the feedback synapse reveal that the synaptic gain is light-dependent with the highest negative gain near the dark horizontal cell potential. The horizontal cell-cone feedback synapse improves the reliability of the photoreceptor output synapses. It also modulates the dynamic range and mediates color opponency and surround responses in second-order retinal neurons.

Passive and active ion fluxes across membranes of mammalian cells are known to be sensitive to changes in ambient temperature, thus, in general, cell potentials are also expected to be temperature sen

Six voltaic cells have been evaluated for their suitability in the determination of thermodynamic parameters. The cells were prepared with all species present at conditions that approximate standard-state conditions and cell potentials were measured as a function of temperature. From these measurements graphs of voltage versus temperature were prepared. From these graphs it was possible to determine the standard heats of reaction (ΔIIrxn), standard change in entropy or disorder (ΔS°rxn), and the Gibbs free energy (ΔG°rxn) for the spontaneous oxidation-reduction reactions. The standard cell potential (E°cell values were also calculated. Two cells with opposite temperature dependence of the cell potential were found to produce good agreement with the literature values of ΔG°rxn, ΔH°rxn, ΔS°rxn and E°cell. Criteria for identifying additional cells that may be suitable for potentiometric studies of thermodynamic parameters are also included.

Recent studies have shown potential ways for improving stem cell cryopreservation. The major need for autologous stem cell use is a long-term storage: this arises from the humans' hope of future use of their own cells. Therefore, it is important to evaluate the cell potential of vitality and differentiation before and after cryopreservation. Although several studies have shown a long-term preservation of adipose tissue, a few of them focused their attention to stem cells. The aim of this study was to evaluate the fate of cryopreserved stem cells collected from adipose tissue and stored at low a temperature in liquid nitrogen through an optimal cryopreservation solution (using slowly cooling in 6% threalose, 4% dimethyl sulfoxide, and 10% fetal bovine serum) and to develop a novel approach to efficiently preserve adipose-derived stem cells (ASCs) for future clinical applications. Results showed that stem cells, after being thawed, are still capable of differentiation and express all surface antigens detected before storage, confirming the integrity of their biology. In particular, ASCs differentiated into adipocytes, showed diffuse positivity for PPARγ and adiponectin, and were also able to differentiate into endothelial cells without addition of angiogenic factors. Therefore, ASCs can be long-term cryopreserved, and this, due to their great numbers, is an attractive tool for clinical applications as well as of impact for the derived market. © 2009 Mary Ann Liebert, Inc. Recent studies have shown potential ways for improving stem cell cryopreservation. The major need for autologous stem cell use is a long-term storage: this arises from the humans' hope of future use of their own cells. Therefore, it is important to evaluate the cell potential of vitality and differentiation before and after cryopreservation. Although several studies have shown a long-term preservation of adipose tissue, a few of them focused their attention to stem cells. The aim of this study was to evaluate the fate of cryopreserved stem cells collected from adipose tissue and stored at low a temperature in liquid nitrogen through an optimal cryopreservation solution (using slowly cooling in 6% threalose, 4% dimethyl sulfoxide, and 10% fetal bovine serum) and to develop a novel approach to efficiently preserve adipose-derived stem cells (ASCs) for future clinical applications. Results showed that stem cells, after being thawed, are still capable of differentiation and express all surface antigens detected before storage, confirming the integrity of their biology. In particular, ASCs differentiated into adipocytes, showed diffuse positivity for PPARγ and adiponectin, and were also able to differentiate into endothelial cells without addition of angiogenic factors. Therefore, ASCs can be long-term cryopreserved, and this, due to their great numbers, is an attractive tool for clinical applications as well as of impact for the derived market. © 2009 Mary Ann Liebert, Inc.

The capacity of Li/V2O5 batteries is improved by the extension of the usual cycling domain from 0 ⩽ x ⩽ 1 to 0 ⩽ x ⩽ 1.8. Such behavior is attributed to the formation of a γ-LiV2O5 bronze for x ⩾ 1. Reversible deintercalation of lithium from the γ-phase leads to a new form of V2O5 that explains the enhancement of cell potential.