Showing papers in "Journal of The Electrochemical Society in 1981"
TL;DR: In this paper, the concept of all-solid composite electrodes is presented, which contains a finely dispersed reactant,, in a solid mixed-conducting matrix, and the polarization is found to be comparable to values typical of highly porous electrode systems in molten salt electrolytes.
Abstract: The concept of a novel all‐solid composite electrode is presented. One example of such a composite contains a finely dispersed reactant, , in a solid mixed‐conducting matrix, . Repeated charging and discharging of such electrodes without appreciable loss of capacity has been demonstrated. The polarization is found to be comparable to values typical of highly porous electrode systems in molten salt electrolytes.
1,113 citations
TL;DR: In this paper, a model based on the movement of point defects in an electrostatic field is proposed to interpret the growth behavior of a passive film on a metal surface, which results in a logarithmic growth law.
Abstract: A model based on the movement of point defects in an electrostatic field is proposed to interpret the growth behavior of a passive film on a metal surface. This model results in a logarithmic growth law. The theoretical equations derived from the model readily account for experimental data for the growth of a passive film on iron. It is found that the field strength of the film is . The dependence of film/solution interface potential difference on the applied potential (α) was found to be 0.743, and is independent of the identity of the anion in solution. However, the dependence of the potential difference across the film/solution interface on the solutionpH (β) is strongly dependent on the identity of the solution anion.
705 citations
TL;DR: In this article, the point defect model was extended to account for chemical breakdown, and the dependence of the breakdown potential on halide concentration and incubation time breakdown overpotential relationships was investigated.
Abstract: The point defect model that was previously developed (1) to explain the growth kinetics of a passive film has been extended to account for chemical breakdown. This model provides quantitative explanations of the dependence of breakdown potential on halide concentration, and of the incubation time‐breakdown overpotential relationships that have been observed for iron and nickel in aqueous solutions. Limitations of the model are identified and discussed.
551 citations
TL;DR: In this article, self-diffusion coefficients for sodium ion, cesium ion, and water have been measured for Nafion® 120 perfluorosulfonate ion exchange membranes.
Abstract: Membrane self‐diffusion coefficients for sodium ion, cesium ion, and water have been measured for Nafion® 120 perfluorosulfonate ion exchange membranes. Values have been determined as a function of temperature, and as a function of membrane water content by studying samples in heteroionic forms. The diffusional properties of this polymer are found to differ from those of conventional polystyrenesulfonates in several respects, and the free volume theory which describes ionic diffusion in the latter is inappropriate to treat Nafion. Results indicate that cations may exist in two distinct regions in the polymer; the proportion of total cations in each region may depend on the ions size and charge density. A structural model of Nafion, which correlates the membrane's spectroscopic and diffusional properties, is proposed to explain the results.
511 citations
TL;DR: The defect chemistry of polycrystalline has been studied by means of the equilibrium electrical conductivity as a function of temperature, oxygen activity, Sr/Ti ratio, and impurity additions as mentioned in this paper.
Abstract: The defect chemistry of polycrystalline has been studied by means of the equilibrium electrical conductivity as a function of temperature, oxygen activity, Sr/Ti ratio, and impurity additions. Reduction, excess , and acceptor impurities all contribute to the oxygen vacancy content and their effects are therefore highly interdependent. The effect of added donor‐impurities,e.g., 500 ppm Nb, is highly dependent on the presence and amount of excess .
396 citations
TL;DR: In this paper, the steady state polarization curves and electrode impedances were measured during the dissolution of iron in solution acidified by the addition of, and the experimental results were quantitatively interpreted by computer simulation on the basis of a reaction model including three dissolution paths.
Abstract: Steady‐state polarization curves and electrode impedances were measured during the dissolution of iron in solution acidified by the addition of . These experiments were performed within very widepH (0–5), current density (up to 0.1 A cm−2), and frequency (10−3–105 Hz) ranges. Three time constants, in addition to the high‐frequency capacitive loop attributed to the double layer capacity and the charge transfer resistance, were observed before the onset of the passivation process. The experimental results were quantitatively interpreted by computer simulation on the basis of a reaction model including three dissolution paths. At low current densities, the dissolution path, which can be related to the consecutive mechanism, controls the overall rate. At higher current densities, a self‐catalytic path, implying a ferrous intermediate, determines the overall current. Another self‐catalytic path, with monovalent iron, plays an important role in the electrode impedance and the prepassivation process although its contribution to the current is not prevalent at any pH.
393 citations
TL;DR: In this paper, a 6% doped polyacetylene film (; 3 mg) exhibited an open circuit voltage of 3.7V and an initial short-circuit current of 25 mA.
Abstract: Polyacetylene, can be controllably doped electrochemically through the semiconducting to the metallic regime using a solution of in propylene carbonate and a lithium cathode. Flexible, golden, free‐standing films of having conductivities up to ~103Ω−1 cm−1 are readily obtained. Electrochemical "undoping" of the allows this doped film to be used as the cathode‐active material in lightweight rechargeable storage batteries. The overall complete discharge reaction isA 0.5 cm2 piece of the 6% doped film (; ~3 mg) exhibited an open‐circuit voltage of 3.7V and an initial short‐circuit current of 25 mA. No change in the open‐circuit voltage characteristics of a battery could be detected even after 326 successive constant current partial charge/discharge cycles. No degradation of the polyacetylene electrode was observed. Experimental energy densities of ~176 W‐hr/Kg were obtained based on the weight of the initially employed and the weight of Li consumed (exclusive of weights of electrolyte, solvent, and packaging material) during partial discharge when was converted to.
338 citations
TL;DR: In this article, a thermodynamic study of the lithium-tin system was made using galvanic cells of the type over the temperature range from 360° to 590°C.
Abstract: A thermodynamic study of the lithium‐tin system was made using galvanic cells of the type over the temperature range from 360° to 590°C. The composition of the alloy was varied from pure tin to 86 a/o Li using the coulometric titration technique. Coulometric titration curves showed that six intermediate phases exist, with nominal stoichiometric compositions , , , , , and . At low lithium concentrations, the activity of lithium in molten lithium‐tin alloys follows Henry's law behavior. The partial and integral molar thermodynamic properties of the lithium‐tin system were evaluated as a function of composition from emf measurements at 415°C. The temperature dependence of the standard Gibbs free energies of formation for the six intermediate phases was also determined. The experimental results were used to map out parts of the phase diagram of the lithium‐tin system. The homogeneity ranges of the six solid phases are all quite narrow. The phase congruently melts at about 488°C and the phase peritectically decomposes at 500°C. These two phases form an eutectic mixture of 57 a/o Li at 470°C. The liquidus line on the tin‐rich side of the binary phase diagram was found to agree with data reported in literature.
232 citations
TL;DR: In this article, the chemical etching characteristics of various etching solutions were studied through an optical mask in the solutions of various systems: (i), (ii), (iii), (iv), (v), and (v).
Abstract: The chemical etching characteristics of are studied through an mask in the solutions of various etching systems: (i) , (ii) , (iii) , (iv) , and (v) . The etched depth is evaluated by using a calibrated optical microscope. The etching profiles are examined by cleaving the wafer in orthogonal directions along the (110) and (10) planes. Various etching profiles, such as V‐shaped, reverse mesashaped ones, and nearly vertical walls, are formed by stripes being etched on the (001) planes. The indexes of the etch‐revealed planes are identified by making a comparison with the calculated angle between the (001) surface and etch‐side plane. The utility of these etching solutions is also discussed for a variety of device applications.
216 citations
TL;DR: In this article, the corrosion rate of copper in laboratory tests is shown to be a sensitive function of relative humidity, sulfur dioxide, hydrogen sulfide, ozone, hydrogen chloride, and chlorine concentrations.
Abstract: The corrosion rate of copper in laboratory tests is shown to be a sensitive function of relative humidity, sulfur dioxide, hydrogen sulfide, ozone, hydrogen chloride, and chlorine concentrations. Observed indoor corrosion rates obey log normal statistics over the field population of this study. Also, the observed indoor rates correlate reasonably well with the measured reduced sulfur concentrations (, ). The corrosion rate of silver is shown not to be humidity dependent. Hydrogen sulfide, ozone, chlorine, and hydrogen chloride concentrations substantially influence its corrosion rate. The observed indoor rates obey log normal statistics and correlate well with the reduced sulfur gas concentration. In contrast to copper, where indoor rates are 1% of outdoor values, silver often corrodes faster indoors than outdoors. Its sensitivity to sulfur gases and insensitivity to relative humidity is proposed as a plausible explanation for these findings. It is proposed that metallic silver is stable in polluted acidic atmospheric environments and therefore is the dominant surface species while is present on the surface of copper. The thermochemistry and kinetics of these two surfaces will control the stability of silver and copper, respectively, in the presence of pollutants.
211 citations
TL;DR: In this paper, the properties of iron in n-type and p-type silicon were studied by means of DLTS, carrier lifetime measurements, and infrared absorption spectroscopy, and the activation energy was determined to be.
Abstract: The properties of iron in n‐type and p‐type silicon were studied by means of DLTS, carrier lifetime measurements, and infrared absorption spectroscopy. Only one donor level was observed, situated at and correlated to iron on an interstitial site. In p‐Si:B iron‐boron pairs were formed at room temperature. Their activation energy was determined to be . The reaction proceeded in two phases. In the second phase a thermal equilibrium between iron and iron‐boron pairs was found which could be shifted by annealing and illuminating the specimen, respectively. In aluminum‐doped silicon crystals two levels were observed after iron diffusion correlated to iron‐aluminum pairs. Their activation energies were determined to be . It is assumed that iron‐boron pairs form also two levels, a donor and an acceptor. The acceptor must be situated in the upper half of the silicon bandgap. Reaction mechanisms are discussed.
TL;DR: In this paper, the impedance spectrum for a passivated electrode has been computed using the point defect model that was proposed earlier, and the model predicts that at high frequencies the film/solution interfacial reaction is predominant and thus a variety of semicircles can be observed in the complex impedance plane.
Abstract: The impedance spectrum for a passivated electrode has been computed using the point defect model that was proposed earlier (6, 7). This model predicts that at high frequencies the film/solution interfacial reaction is predominant and thus a variety of semicircles can be observed in the complex impedance plane. At low frequencies, the transport of point defects in the passive film is rate controlling, and a Warburg‐type impedance spectrum is predicted. These predictions are in good agreement with experimental data for passive Ni and Type 304 SS in aqueous buffer systems.
TL;DR: In this paper, the origins of electrode impedances are examined on the basis of experimental results given in Part I, and hypotheses describing reaction rates, such as the Tafel law, reaction reversibility, and the adsorption isotherm law, are analyzed in order to translate reasonably the reaction models into mathematical expressions.
Abstract: The electrode impedance determined experimentally shows a certain number of time constants as capacitive or inductive features. These impedances arise from various processes occurring at or near the electrode interface, such as charge transfer, adsorption‐desorption of reaction intermediate species, changes of the roughness factor, changes of the number of active sites or of volume concentration in the vicinity of the electrode, etc. The origins of impedances are examined on the basis of experimental results given in Part I . Then, hypotheses describing reaction rates, such as the Tafel law, reaction reversibility, and the adsorption isotherm law, are analyzed in order to translate reasonably the reaction models into mathematical expressions. With hypotheses retained, it is concluded that the experimental results should be interpreted by a model including three adsorbed reaction intermediate species. Forty possible reaction schemes, as the complete set of prospective models, were written and examined according to both steady‐state polarization curves and electrode impedances. The appearance of two current maxima implies at least two dissolution paths in the reaction models and allowed us to eliminate 10 of the 40 reaction schemes. On the other hand, the appearance of inductive impedance was found to constitute a very selective criterion. Only one model, given in Part I , was found to simulate suitably the whole set of experimental results.
TL;DR: In this paper, physicochemical properties of the mixed solvents of propylene carbonate and 1,2-dimethoxyethane dissolving various salts have been measured at 30/degree/C, in order to clarify the mixing effect of the organic electrolytes for high energy density batteries.
Abstract: Some physicochemical properties of the mixed solvents of propylene carbonate and 1,2-dimethoxyethane dissolving various salts have been measured at 30/degree/C, in order to clarify the mixing effect of the organic electrolytes for high energy density batteries. The vapor pressure and laser Raman spectra of the mixed solvents provided significant information regarding the solvent-solvent interactions. Ionic conductiviies under infinite dilution condition were determined by the measured molar conductivities of the salts and transport numbers of the ions; the Stokes' radii of the ions in the mixed solvents were also estimated. A specific solvation of cations with 1,2-dimethoxyethane in the mixed solvents seems to give captured cations like a crown ether does. 16 refs.
TL;DR: In this article, Corrosion resistant ZnCo alloys were electrodeposited on the steel sheet cathode from an acid galvanizing bath containing a small amount of cobalt sulfate.
Abstract: Corrosion resistant Zn‐Co alloys were electrodeposited on the steel sheet cathode from an acid galvanizing bath containing a small amount of cobalt sulfate. Under most of the plating conditions studied, the anomalous codeposition and, hence, the preferential deposition of electrochemically less noble Zn occurred. The electrodeposition process of the alloy including the Zn hydroxide formation resulting from the rise in pH in the vicinity of the cathode was estimated by electrochemical and spectroscopic studies.
TL;DR: The phase diagram of the Bi2O3-Er 2O3 system was investigated in this paper and a monophasic f c c c structure was stabilized for samples containing 17.5-45.5 mol% Er2O 3.
Abstract: The phase diagram of the Bi2O3-Er2O3 system was investigated. A monophasic f c c structure was stabilized for samples containing 17.5–45.5 mol% Er2O3. Above and below this concentration range polyphasic regions appear. The f c c phase showed high oxygen ion conduction. The ionic transference number is equal to one for specimens containing 30 mol% Er2O3 or less, while an electronic component is introduced at low temperatures for specimens containing 40–60 mol% Er2O3. Between 673 K and 873 K a maximum in the conductivity was found at 20 mol% Er2O3. (Bi2O3)0.8.(Er2O3)0.20 is found to be the best oxygen ion conductor so far known. The conductivity at 773 K and 973 K is 2.3 Ω−1m−1 and 37 Ω−1 m−1 respectively. These values are 2–3 times higher than the best oxygen ion conductor reported for substituted Bi2O3 systems and 50–100 times higher than those of stabilized zirconia (ZrO2)0.915(Y2O3)0.085 at corresponding temperatures.
TL;DR: In this article, a defect model for the undoped crystals is proposed, according to which, the crystals are essentially intrinsic at the equilibration temperatures and the native acceptor defects are doubly ionized.
Abstract: Undoped crystals were subjected to high temperature equilibration at temperatures ranging from 400° to 655°C in various Hg atmospheres. Hall effect and mobility measurements were carried out on the crystals quenched to room temperature subsequent to the high temperature equilibration. The variation of the hole concentration in the cooled crystals at 77 K as a function of the partial pressure of Hg at the equilibration temperatures, together with a comparison of the hole mobility in the undoped samples with that in the copper‐doped samples, has yielded a defect model for the undoped crystals, according to which, the undoped crystals are essentially intrinsic at the equilibration temperatures and the native acceptor defects are doubly ionized. Native donor defects appear to be negligible in concentration, implying that the p‐to‐n conversion in these alloys is mainly due to residual foreign donor impurities. The thermodynamic constants for the intrinsic excitation process as well as for the incorporation of the doubly ionized native acceptor defects in the undoped crystals have been arrived at. Copper appears to be incorporated on metal lattice sites acting as a single acceptor with little compensation. Results on the heavily copper‐doped samples indicate that the quench from the equilibration temperatures was imperfect resulting in a large fraction of the copper precipitating during the quench. From results of experiments where the cooling rate from the equilibration temperatures was intentionally varied in the undoped samples, a qualitative correlation was established between the quenching efficiency and the presence of macroscopic defects such as voids and inclusions in the samples.
TL;DR: In this article, a 100 cm2 single cell with a microporous plastic separator has been cycled at a current density of 60 mA/cm2 at 60°C.
Abstract: The iron‐redox battery is a low power density energy storage device that may be attractive for applications such as load leveling and solar energy storage. During the charge cycle of this battery, the ferrous ion from an aqueous chloride electrolyte plates onto the negative electrode and is oxidized to ferric ion at the positive electrode. A solid graphite or titanium plate can be used for the iron electrode while a high specific area material is necessary for the redox electrode. A 100 cm2 single cell with a microporous plastic separator has been cycled at a current density of 60 mA/cm2 at 60°C. The cell was capable of storing and discharging energy at a round trip current efficiency of 90% and an energy efficiency of 50%, with a maximum discharge power density of 50 mW/cm2. The largest voltage losses occurred at the iron electrode and to a lesser extent at the redox electrode. Factors affecting voltaic and coulombic losses including electrolyte composition and temperature, cell separators, electrode materials, and electrolyte additives have been studied and the results reported.
TL;DR: In this paper, the infrared spectra, deposition rate, density, etch rate, stress, refractive index, step coverage, breakdown voltage, and annealing behavior of silicon dioxide films were measured.
Abstract: Silicon dioxide films have been deposited by reacting silane and nitrous oxide in a parallel‐plate, radial flow, plasma reactor. Deposition parameters (temperature, power, and gas composition) have been systematically varied, and the films characterized by measuring the infrared spectra, deposition rate, density, etch rate, stress, refractive index, step coverage, breakdown voltage, and annealing behavior. The films, deposited at 100°–340°C and at rates of 200–360 A/min, contain 2–9 a/o H bonded as , , and . The films have densities of about 2.3 g/cm3, refractive indexes of about 1.47, a compressive stress usually less than , and etch rates about twelve times faster than thermally grown silicon dioxide. Films deposited below 200°C or at high power etch nonuniformly with part of the film etching very fast, possibly indicating a two‐phase mixture. The step coverage is not conformal and the films are thin along vertical step walls. The films breakdown at fields of 4–10 MV/cm. During annealing in air at temperatures up to 400°C, the films lose hydrogen and become less dense, but do not crack. The properties of the plasma‐deposited silicon dioxide are strongly dependent on the specific deposition conditions. In addition, simple correlations between the properties do not exist. Thus in characterizing plasma deposited silicon dioxide, the exact deposition conditions must be specified and all the film properties of interest must be measured.
IBM1
TL;DR: In this article, the authors studied the mechanism of plasmaenhanced vapor deposition of silicon nitride by varying process parameters, such as substrate temperature, rf power, reactant gas ratio, and total pressure.
Abstract: The mechanism of plasma‐enhanced vapor deposition of silicon nitride is studied by varying process parameters, such as substrate temperature, rf power, reactant gas ratio, and total pressure. The film composition (Si, N, O, and H) is determined by electron microprobe and infrared analysis. From these analyses, it is established that the film composition is determined not only by the reactant gas ratio, but also by a combined function of the rf power and total pressure in terms of , with a system‐dependent factor. The dependence of film composition on can be related to the radical generation processes. The substrate temperature is found to affect the film composition as well. Greater substrate temperature produces films with less hydrogen and more nitrogen, and hence, higher density. The film dielectric property and plasma etching rate are both studied and found to be dependent on the film composition. Finally, a three‐step deposition mechanism, namely, radical generation, radical adsorption, and adatom rearrangement, is proposed to explain the reaction scheme, and an ion incorporation mechanism is proposed to explain the change of film physical properties.
TL;DR: In this paper, the authors measured ionic and electronic conductivities and thermoelectric power for AgI and AgI containing a dispersion of submicron size Al2O3 particles.
Abstract: Ionic and electronic conductivities, and thermoelectric power have been measured for AgI and AgI containing a dispersion of submicron size Al2O3 particles. While the dispersion of Al2O3 enhances the ionic conductivity significantly, it does not affect the electronic properties of the matrix. The enhancement is a strong function of the size and concentration of the dispersoid. Various models have been tested to account for the enhanced conduction. However, the complex behavior of the present results points out the need for more sophisticated theoretical models. Ionic conduction and thermoelectric power data suggest that the dispersed Al2O3 generates an excess of cation vacancies and thereby enhances the conductivity and suppresses the thermoelectric power of the matrix. The individual heats of transport of cation interstitials and vacancies have been estimated and compared to their respective migration energies.
TL;DR: In this paper, a new type of superlattice in consisting of a periodic sequence of ultrathin p and n-doped layers has been achieved by molecular beam epitaxy (MBE).
Abstract: A new type of superlattice in consisting of a periodic sequence of ultrathin p‐ and n‐doped layers (also called "nipi" crystal) has been achieved by molecular beam epitaxy (MBE). The individual p‐ and n‐type layers of which the structure is composed were doped with beryllium as acceptor and silicon as donor impurities, respectively. Low temperature photoluminescence studies and transport measurements were performed first to attest a superior quality of the intentionally p‐ and n‐doped constituent layers and of the characteristics of the individual p‐n junctions prepared by MBE. The existence of a novel superlattice effect in the periodic p‐n doping multilayer structures in was then established by studying the optical absorption tails which extend far into the gap of the unmodulated semiconductor depending on the constituent doping levels and on the artificially introduced periodicity of the crystal.
TL;DR: In this paper, dissolution of electrochromic (EC) films in aqueous media was studied and the results strongly suggest that EC films formed by evaporation are amorphous molecular solids consisting of trimeric molecules bound weakly to each other through water−bridge, hydrogen, and van der Waal's bonding.
Abstract: Despite much investigation of the electrochromic (EC) coloration process in films, such displays have not yet become commercially viable because of limited useful device life. Device degradation occurs by film dissolution on the shelf and erosion during cycling. Water plays a crucial role in both efficient coloring/bleaching and in film degradation. To better understand the degradation process and the role of water, dissolution of EC films in aqueous media was studied. The results strongly suggest that EC films formed by evaporation are amorphous molecular solids consisting of trimeric molecules bound weakly to each other through water‐bridge, hydrogen, and van der Waal's bonding. The nature of this microstructure is responsible for the high solubility. Films subjected to ion bombardment show decreased dissolution rates as well as decreased electrochromism and, while amorphous, are believed to have a random network rather than molecular microstructure.
TL;DR: In this article, the rotating ring disk electrode has been applied to the related phenomena of dissolution, current oscillation, and passivation of zinc in concentrated aqueous, and a physical model was proposed to describe the anodic behavior of zinc.
Abstract: The rotating ring‐disk electrode has been applied in this study to the related phenomena of dissolution, current oscillation, and passivation of zinc in concentrated aqueous . The results of potentiostatic and potentiodynamic experiments are compared with those of previous workers, and a physical model is proposed to describe the anodic behavior of zinc in four successive potential regions: active dissolution, prepassivation, pseudopassivation, and true passivation.
TL;DR: In this article, the composition of the films and the deposition efficiency were determined as a function of current density, pH, the identity of the anion ( or Cl−), and the boric acid content of the solution.
Abstract: Films of alloys were deposited under galvanostatic conditions from solutions containing no stress‐relieving additives and no surfactants. The composition of the films and the deposition efficiency were determined as a function of current density, pH, the identity of the anion ( or Cl−), and the boric acid content of the solution. The Fe content is lower in deposits from chloride solution than from sulfate solution and is increased by the addition of . The efficiency increases with increasing current density and increasingpH, is higher in deposits from chloride solution, and is little affected by . The observations are interpreted in terms of suppression of Ni deposition by a surface iron hydroxide precipitated when the local surfacepH rises during deposition. The way in which the solution components and conditions of deposition influence the formation of this hydroxide determines their effect on deposit properties. Increasing current density causes greater hydroxide precipitation and thus increases the Fe content of the film up to the point where ionic diffusion in the hydroxide limits the rate of Fe deposition. Chloride ion forms a weak complex with Fe2+ and thereby limits hydroxide formation, lowering the percentage Fe in the deposits. Boric acid has its greatest effect under conditions where hydroxide formation is most extensive. It does not act as a buffer, but apparently adsorbs on the hydroxide‐covered surface.
TL;DR: In this paper, the initial electrocatalytic activity for oxygen evolution in acid electrolyte was determined using the potentiostatic method, and the surface areas of these oxides were estimated using cyclic voltammetry.
Abstract: Ruthenium oxide, prepared by the thermal decomposition method, has the highest known initial electrocatalytic activity for oxygen evolution in acid electrolyte. However, this material is not stable in the electrolyte and at the same time exhibits a significant increase of oxygen overpotential with time, probably due to a chemical transformation of the oxide from a lower to a higher valence state. Efforts were made to stabilize ruthenium by preparing mixed oxides with Ir and/or Ta using the thermal decomposition method. The electrocatalytic activities for oxygen evolution on these oxides in were determined using the potentiostatic method. The surface areas of these oxides were estimated using cyclic voltammetry. Dual Tafel slopes (approximately 30 and 40 mV) were found on most of these oxides. The ternary oxide exhibited a single Tafel slope of 30 mV, had the lowest overpotential, and showed minimum variation of overpotential with time.
TL;DR: In this paper, the authors examined the suitability of aquo iron (II)-iron (III)-complexes with o-phenanthroline and related ligands for electrochemical energy storage.
Abstract: Iron (III)-Iron (II) complexes with o-phenanthroline and related ligands have been examined by electrochemical techniques in aqueous H2SO4 media with respect to their suitability as redox couples for electrochemical energy storage. The iron (II) complexes undergo a rapid 1 electron oxidation at graphite and platinum electrodes to yield iron (III) complexes; these complexes showed varying stabilities depending on the nature of the substituents on the complexes. The iron (II) complexes examined in this study were formed with (i) monodentate, (ii) bidentate, or (iii) tridentate ligands. The redox couples have a higher E o value which has been a positive consideration in the storage. Although the aquo iron (II)- iron (III) couple has an E o less than the complexes, it certainly has shown "greater promise in terms of storage stability. The kinetics of iron (II) complexation~has been followed by cyclic voltammetry.
TL;DR: In this article, the Butler-Volmer equation is obeyed with cathodic and anodic transfer coefficients of and, respectively, and an effective exchange current which varies as the power of.
Abstract: The nature of electrode polarization, previously investigated for Pt paste electrodes, is now studied for Pt foil, Ag and Au paste, and Ag foil electrodes. The current interruption method with a reference electrode is employed in the temperature range 500°–800°C under gas mixtures. Electrode structures are also examined by optical and electron microscopy. The principal experimental feature is that the Butler‐Volmer equation is obeyed with cathodic and anodic transfer coefficients of and , respectively, and an effective exchange current which varies as the power of . Also, transient decay curves are much slower than for the pure charge transfer mechanism. These features can be interpreted in terms of a model in which charge transfer takes place in the two‐phase region between electrode and electrolyte, but where the rate is controlled by interfacial diffusion of oxygen atoms along the electrode, except when the electrode particles are extremely small. For extreme cases of diffusion limitation, the adatom concentration over most of the two‐phase region becomes so low that electrolyte reduction takes place. The resulting appreciable electronic contribution can be treated in terms of the Wagner polarization‐cell theory.