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Showing papers in "Journal of Applied Electrochemistry in 1977"


Journal ArticleDOI
TL;DR: In this paper, a modified version of redox catalysis was found to be a modified "redox" catalysis, where O2 molecules and the products of their reaction remain strongly co-ordinated to the central metal ion of the chelates XMeII.
Abstract: The electro-reduction of oxygen is effectively catalysed by metal chelates of the N4-type. The mechanism of this process has been found to be a modified ‘redox catalysis’. O2 molecules and the products of their reaction, at least up to H2O2, remain strongly co-ordinated to the central metal ion of the chelates XMeII. The potential-determining step, which regenerates the reduced form, is the following: (XMeIII...O2H)++H++ 2e→XMeII+H2O2.

168 citations


Journal ArticleDOI
TL;DR: In this paper, a characteristic morphology and crystal orientation for zinc deposits electrowon from high purity synthetic and industrial acid sulphate electrolytes was obtained for a wide range of experimental conditions which included variations in the applied current density and changes in the anode materials and cathode pretreatments.
Abstract: A characteristic morphology and crystal orientation; namely (112) (114) (102), has been obtained for zinc deposits electrowon from high purity synthetic and industrial acid sulphate electrolytes. These deposit characteristics persisted over a wide range of experimental conditions which included variations in the applied current density and changes in the anode materials and cathode pretreatments. The addition of either antimony or glue to the electrolyte produced deposit morphologies and orientations which were distinctly different from those obtained for addition-free electrolytes. When both antimony and glue additions were made to the electrolyte, however, the deposit morphologies and crystal orientations were similar to those obtained from addition-free solutions. The various deposit morphologies and orientations obtained were shown to correlate with changes occurring in the zinc deposition overvoltage.

86 citations


Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate that it is possible to measure the impedances of an electrochemical generator by means of a transfer function analyser over a very wide frequency range.
Abstract: Relatively few works have been carried out on Pb/H2 SO4 batteries from an electrochemical kinetics point of view This is partly due to the complexity of the chemical and electrochemical reactions occurring on plates but mainly because the system is not a constant one The current continuously modifies the electrode structures and their properties [1-3], so that, strictly speaking, no steady-state can be defined in this system Thus, it is scarcely possible to use the classical methods of electrochemical kinetic investigations such as the analysis of polarization curves The use of transient methods seems to be more adequate to investigate the electrode processes of such systems If the system is disturbed by a very small measuring signal so that its response remains linear, its impedance can be defined This allows the analysis of the dynamic behaviour of the system [4] If the direct polarizing current (bias current) I is equal to zero and also if the autodischarge of the battery is negligible, the structure and properties of both plates may be regarded as constant In this particular case, the steady-state can be defined On the contrary, during the charge or discharge processes of a battery, if the measuring period is short enough, the evolution of the electrode structure and other properties affecting cell impedance may be kept to the same order of magnitude or smaller than the errors of measurement In this case, the system under investigation is considered to be in quasi-steady-state Of course, the lowest frequency at which the impedance can be properly explored depends on the measuring error and also on the rate at which the system changes The purpose of this note is to demonstrate that it is technically possible to measure the impedances of electrochemical generators by means of a transfer function analyser over a very wide frequency range The impedance measurements are performed between two terminals of a battery, corresponding to the overall dynamic behaviour of the cell, as well as separately on positive and negative plates Some preliminary results obtained on a commercially available Pb/H2 SO4 battery during a charge and discharge cycle are given

64 citations


Journal ArticleDOI
TL;DR: In this article, the authors examined the cathodic current blackening of Bi2O3-based oxide ion conductors at low oxygen pressure and found that more than 500 mA cm−2 d.c. could be passed at 600°C without causing changes in the electrolyte itself.
Abstract: The cathodic current blackening of Bi2O3-based oxide ion conductors was examined for the Bi2O3-Y2O3 electrolyte at low oxygen pressure. In air, more than 500 mA cm−2 d.c. could be passed at 600° C without causing changes in the electrolyte itself. However, in argon gas, a limiting current of 3 mA cm−2 was observed and the electrolyte was blackened at the cathode side. The limiting current was ascribed to control by the diffusion of oxygen gas at the cathode. The blackened oxide was found to consist of a mixture of Bi metal and Bi2O3-Y2O3 solid solution and to exhibit the equilibrium oxygen partial pressure almost corresponding to that of the Bi, Bi2O3 mixture.

63 citations


Journal ArticleDOI
TL;DR: In this paper, pH titration data suggested the formation of a weak complex, Ni(H2BO3)2, (logK ∼ 3.8 to 4.9) between Ni2+ and H3BO3 in mixed chloride-sulphate electrolytes at 55° C.
Abstract: Buffer capacity studies, carried out using pH titrations, demonstrated that electrolytes containing NiSO4 + H3BO3 + Na2SO4 buffer more effectively than in the presence of H3BO3 + Na2SO4. The increased buffer capacity is dependent on the concentration of both Ni2+ and H3BO3. Thermodynamic analysis of the pH titration data suggested the formation of a weak complex, Ni(H2BO3)2, (logK ∼ 3.8 to 4.9) between Ni2+ and H3BO3 in mixed chloride-sulphate electrolytes at 55° C.

62 citations


Journal ArticleDOI
TL;DR: In this article, Teflon-bonded high surface area carbon, loaded with electrocatalysts, was used for photo-electrochemical cell (P. E. C).
Abstract: Electrodes for the sulphide/sulphur (polysulphide) redox system are described which show low polarization when operated under conditions to be expected in a practical photo-electrochemical cell (P. E. C.)-These electrodes are composed of Teflon-bonded high surface area carbon, loaded with electrocatalysts, the best results having been obtained using cobalt as electrocatalyst.

61 citations


Journal ArticleDOI
TL;DR: In this paper, the conduction behavior in sintered oxides of MoO3-doped Bi2O3, the electrical conductivity in air and the EMF of oxygen gas concentration cell were measured with respect to the phase relation determined by X-ray diffraction.
Abstract: In order to examine the conduction behaviour in the sintered oxides of MoO3-doped Bi2O3, the electrical conductivity in air and the EMF of oxygen gas concentration cell were measured with respect to the phase relation determined by X-ray diffraction

59 citations


Journal ArticleDOI
TL;DR: In this article, the partial electronic conduction in the high oxide ion conductor of the system Bi2O3-Y 2O3 under low oxygen pressure, e.g., polarization methods were employed.
Abstract: In order to investigate the partial electronic conduction in the high oxide ion conductor of the system Bi2O3-Y2O3 under low oxygen pressure, e.m.f. and polarization methods were employed. Although the electrolyte was decomposed when the $$P_{{\text{O}}_{\text{2}} }$$ was lower than the equilibrium $$P_{{\text{O}}_{\text{2}} }$$ of Bi, Bi2O3 mixture at each temperature, the ionic transport number was found to be close to unity above that $$P_{{\text{O}}_{\text{2}} }$$ . The hole conductivity (σ p) and the electron conductivity (σ p) could be expressed as follows, $$\begin{gathered} \sigma _p \Omega cm = 5 \cdot 0 \times 10^2 \left( {P_{O_2 } atm^{ - 1} } \right)^{{1 \mathord{\left/ {\vphantom {1 4}} \right. \kern- ulldelimiterspace} 4}} \exp \left[ { - 106 kJ\left( {RT mol} \right)^{ - 1} } \right] \hfill \\ \sigma _p \Omega cm = 3 \cdot 4 \times 10^5 \left( {P_{O_2 } atm^{ - 1} } \right)^{ - {1 \mathord{\left/ {\vphantom {1 4}} \right. \kern- ulldelimiterspace} 4}} \exp \left[ { - 213 kJ\left( {RT mol} \right)^{ - 1} } \right] \hfill \\ \end{gathered} $$ These values were much lower than the oxide ion conductivity under ordinary oxygen pressure.

57 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed that the loss of ATA activity results from the formation of a nonconductive oxide film at the titanium-active layer interface, which is formed by a non-conductive material.
Abstract: The galvanostatic method has been employed for following the time change of the ATA potential in 0.5 N H2SO4. On the basis of the experimental data it is proposed that the loss of ATA activity results from the formation of a non-conductive oxide film at the titanium-active layer interface.

55 citations



Journal ArticleDOI
TL;DR: In this article, an instrument was developed to measure local current densities in the hydrodynamically very difficult region near the turbulence promoter and a general method for the relative evaluation of hydrodynamic conditions has been developed.
Abstract: Many electrochemical processes suffer in varying degrees from mass transfer limitations. These limitations may require operation at considerably less than economic optimum current densities. Mass transfer to a surface may be considerably enhanced by insertion of turbulence promoters in the fluid flow path near the affected surface. An instrument was developed to measure local current densities in the hydrodynamically very difficult region near the turbulence promoter. A general method for the relative evaluation of hydrodynamic conditions has been developed. Generalization of the data permits optimization of hydrodynamic cell design using the promoter shapes investigated.

Journal ArticleDOI
TL;DR: In this article, the authors deal with an experimental study of copper deposition in fluidized bed electrodes from acidified aqueous solutions containing copper and determine overpotential distributions and the amount of copper deposited at various levels within the electrodes.
Abstract: This paper deals with an experimental study of copper deposition in fluidized bed electrodes from acidified aqueous solutions containing copper. Overpotential distributions are determined and the amount of copper deposited at various levels within the electrodes is also measured. Experiments with long duration times allow the variations of current efficiency for recovery to be obtained as a function of current density and fixed bed thickness. These variations could be explained by the existence of dissolution zones within the electrodes.

Journal ArticleDOI
TL;DR: In this article, steadystate and impedance measurements were carried out in oxygenated and deoxygenated sulphuric acid solutions to investigate the effects of dissolved oxygen on stability and impedance.
Abstract: Steady-state and impedance measurements were carried out in oxygenated and deoxygenated sulphuric acid solutions to investigate the effects of dissolved oxygen. Impedance measurements in deoxygenated sulphuric acid were used to determine values ofCo.

Journal ArticleDOI
TL;DR: In this article, the effect of chloride ion on the morphology of electrodeposited copper under different current densities was reported, which indicated the importance of these results in electrowinning copper from electrolytes obtained from a solvent extraction separation process.
Abstract: The effect of chloride ion on the morphology of electrodeposited copper under different current densities is reported. Chloride ion additions to 10 ppm depolarized the cathode reaction resulting in preferred (022) oriented deposits. At higher chloride ion concentration (111) oriented deposits are preferred. The importance of these results in electrowinning copper from electrolytes obtained from a solvent extraction separation process is indicated.

Journal ArticleDOI
TL;DR: In this article, the temperature of the flowing electrolyte solution within the interelectrode gap has been measured by means of miniature bead-thermistors, and the results were consistent with measurements in a region of increased resistivity within the gap such as that provided by the hydrogen bubble-electrolyte layer adjacent to the cathode.
Abstract: The temperature of the flowing electrolyte solution within the inter-electrode gap has been measured by means of miniature bead-thermistors. For NaCl solution the temperatures recorded within the gap are higher than those outwith the gap. As the flow-rate is reduced the temperature within the gap increases to a maximum which corresponds closely to the boiling state of the electrolyte. These results are consistent with measurements in a region of increased resistivity within the gap such as that provided by the hydrogen bubble-electrolyte layer adjacent to the cathode. Similar tests with NaNO3 solution have shown that the temperatures within the gap are much lower with that electrolyte than with NaCl solution. These effects follow previous observations that substantially less hydrogen gas is evolved with NaNO3 than with the NaCl electrolyte.

Journal ArticleDOI
TL;DR: In this article, the electrodeposition of aluminium on brass (63/37) from a dry AlCl3/NaCl melt (80wt.% purified AlCl 3, 20 wt.% NaCl) using static as well as rotating cathodes and a variety of conditions has been studied.
Abstract: The electrodeposition of aluminium on brass (63/37) from a dry AlCl3/NaCl melt (80wt.% purified AlCl3, 20 wt.% NaCl) using static as well as rotating cathodes and a variety of conditions has been studied. The current efficiency of the process is very high and the electrodeposits are smooth, fine grained and silver white in appearance. Although at lower temperatures, there is a tendency for flakes to be formed locally these are easily removed and do not affect the overall quality of the electroplate.

Journal ArticleDOI
TL;DR: In this paper, the performances of typical electro-oxidation catalysts were measured in both electrolytes over a range of concentrations, and it was shown that the reaction rate on the poisoned surfaces is proportional to the water activity.
Abstract: Phosphoric acid and sulphuric acid have been compared as potential electrolytes for methanol-air fuel cells. The performances of typical electro-oxidation catalysts were measured in both electrolytes over a range of concentrations. With all catalysts the activity falls with increasing acid concentration. While this is to some extent due to the decrease in water activity at higher concentrations it seems that with both acids there is significant poisoning of the catalyst. The results can be explained for both electrolytes by assuming that adsorption of undissociated acid poisons the catalyst surfaces and that the reaction rate on the poisoned surfaces is proportional to the water activity.

Journal ArticleDOI
TL;DR: In this article, a simple procedure for the oxidation of benzyl alcohols to aldehydes is described, where the oxidizing agent is hypobromite generated by the anodic oxidation of aqueous bromide and the reactions are carried out in an undivided cell in an amyl acetate/water emulsion containing 2% tetrabutylammonium bisulphate.
Abstract: A simple procedure for the oxidation of benzyl alcohols to aldehydes is described. The oxidizing agent is hypobromite generated by the anodic oxidation of aqueous bromide and the reactions are carried outin situ in an undivided cell in an amyl acetate/water emulsion containing 2% tetrabutylammonium bisulphate.

Journal ArticleDOI
P. M. Robertson1, N. Ibl1
TL;DR: The Swiss roll cell has been used for the removal of copper from dilute synthetic waste waters as mentioned in this paper, and it has shown that in acidic solutions the copper concentration may be taken down to a concentration under 1 ppm.
Abstract: The ‘Swiss-roll’ cell has been used for the removal of copper from dilute synthetic waste waters. Batch experiments have shown that in acidic solutions the copper concentration may be taken down to a concentration under 1 ppm. Without N2-sparging the current efficiency at a concentration of 22 ppm Cu was 30%. The cell was also used to separate metals from mixtures found in pickling baths. Thus 99·9% copper was removed from a Cu/Zn sulphate solution with no detectable change in the Zn concentration. The deposited metal may be leached out chemically or stripped out by anodic polarization.

Journal ArticleDOI
TL;DR: In this paper, le deblocage result of the reaction chimique Hads+1/4 O2→1/2 H2O was shown to be compatible with l'analyse en fonction du potentiel de la correlation entre A+BΩ676 1/2 en supposant the reaction suivante.
Abstract: A l'interface Fe/H2SO4, 1 N (aere ou non), et dans le domaine de potentiel (−0·95, −1·2 V/E.S.S.), nous avons trouve que le courant cathodique mesure sur une electrode a disque tournant varie avec la vitesse de rotation Ω suivant une loi de la forme:I=A+BΩ 1/2. A peut etre identifie au courant de reduction du proton solvate mais depend fortement de la teneur en oxygene de l'electrolyte. La composante diffusionnelleBΩ 1/2 peut etre identifiee a la reduction de l'oxygene dissous mais est tres inferieure a celle relative a une surface uniformement reactive. Le blocage resultant est compatible avec l'analyse en fonction du potentiel de la correlation entreA etBΩ 1/2 en supposant la reaction suivante: Fe Hads⇌Fe H ads * , ou Fe Hads est un hydrogene adsorbe faiblement lie de courte duree de vie (qq. s) et Fe H ads * est un hydrogene adsorbe fortement lie de longue duree de vie (qq.h). Le deblocage resulte de la reaction chimique Hads+1/4 O2→1/2 H2O. Dans le cadre classique du mecanisme de degagement de l'hydrogene en deux etapes, nous avons montre que notre modele d'interdependance implique que l'etape limitant la vitesse soit celle de Tafel a faible surtension et celle d'Horiuti pour des tensions cathodiques plus elevees.

Journal ArticleDOI
TL;DR: In this paper, a laboratory-scale cell for continuous electrolytic reduction of chalcopyrite contained in copper concentrate is described, where dry concentrate is fed into one end of the cell and forms a particulate bed electrode, with fluidized properties, resting on the copper cathode constituting the cell base At the opposite end, the reduced product containing copper sulphide of composition Cu18S to Cu2S flows over a weir.
Abstract: A laboratory-scale cell for the continuous electrolytic reduction of chalcopyrite contained in copper concentrate is described Dry concentrate is fed into one end of the cell and forms a particulate bed electrode, with fluidized properties, resting on the copper cathode constituting the cell base At the opposite end, the reduced product containing copper sulphide of composition Cu18S to Cu2S flows over a weir The feed rate determines the coulombic efficiency and extent of reduction of the sulphide A copper extraction process incorporating slurry electrolysis is proposed and scale-up problems discussed

Journal ArticleDOI
TL;DR: On montre, en etudiant la reduction electrochimique de l'oxygene sur les manganites de nickel dopes en cuivre, Ni1-xCuxMn2O4, que lelectrocatalyse se produit par adsorption sur des sites actifs constitues par des ions Mn4+ associes, en sites octaedriques, a des ion Mn3+.
Abstract: On montre, en etudiant la reduction electrochimique de l'oxygene sur les manganites de nickel dopes en cuivre, Ni1-xCuxMn2O4, que lelectrocatalyse se produit par adsorption sur des sites actifs constitues par des ions Mn4+ associes, en sites octaedriques, a des ions Mn3+.

Journal ArticleDOI
TL;DR: In this paper, the possibility of electrodepositing copper powder by pulsating overpotential was shown, and it was shown that the grain size and the morphology of deposited powder is a function of overpotentials, and of amplitude and frequency of pulsation in constant and pulsatingoverpotential deposition respectively.
Abstract: The possibility of electrodepositing copper powder by pulsating overpotential is shown. These powders are compared to the powders obtained by constant overpotential electrodeposition. It is also shown that the grain size and the morphology of deposited powder is a function of overpotential, and of amplitude and frequency of pulsation in constant and pulsating overpotential deposition respectively.

Journal ArticleDOI
TL;DR: In this paper, a solid electrolyte cell was developed using a high copper ion conductivity solid electrolytes, 7CuBr·C6H12N4CH3Br, a copper anode, and a chalcogen cathode.
Abstract: A solid electrolyte cell has been developed using a high copper ion conductivity solid electrolyte, 7CuBr·C6H12N4CH3Br, a copper anode, and a chalcogen cathode. The open-circuit voltages of the cells with sulphur, selenium, and tellurium as cathode materials were 0·448, 0·373, and 0·258 V, respectively, at 25° C. These cells yielded a current of several tens of microamperes at room temperature and several milliamperes at 114° C without appreciable polarization. An energy density of 4.5 Wh kg−1 at room temperature was evaluated from the weights of the electrolyte and electrode materials for the cell using a selenium cathode in the discharge current density range 60–150μA cm−2.

Journal ArticleDOI
TL;DR: In this paper, high rate anodic dissolution of nickel in sodium nitrate electrolytes was studied under controlled hydrodynamic conditions in order to investigate the influence of electrolyte concentration, pH and temperature on surface brightening under conditions comparable to electrochemical machining.
Abstract: High rate anodic dissolution of nickel in sodium nitrate electrolytes was studied under controlled hydrodynamic conditions in order to investigate the influence of electrolyte concentration, pH and temperature on surface brightening under conditions comparable to electrochemical machining. Dissolution experiments were performed on a rectangular flow channel cell through which the electrolyte was pumped at a constant linear velocity of 1000 cm s−1. Results show that the onset of surface brightening depends on concentration and temperature of the electrolyte but is little affected by pH. The data are consistent with a previously described salt precipitation model for surface brightening.

Journal ArticleDOI
TL;DR: In this paper, a new type of monopolar electrolyser with power leads located on its sides, used for chlorate production, is described and the value of the total cell voltage as well as of local current densities for given current load and given electrode dimensions, interelectrode gap etc.
Abstract: Chemical engineering calculations are performed for a new type of monopolar electrolyser with power leads located on its sides, used for chlorate production. The calculation gives the value of the total cell voltage as well as of local current densities for given current load and given electrode dimensions, interelectrode gap etc. On this basis the optimization of the system is possible.

Journal ArticleDOI
TL;DR: In this article, it was shown that the additive effect of lead acetate on the irregular growth of zinc electrodeposits is connected with a change in the kinetics of the reaction.
Abstract: It is shown that the inhibiting effect of an additive (lead acetate) on the irregular growth of zinc electrodeposits is connected with a change in the kinetics of the reaction. In both alkaline and acid electrolytes, the range of current densities leading to compact deposits is widened by the additive. Simultaneously a shift of the current-potential curves towards more cathodic voltages is observed, and this inhibition rises with an increase of the additive concentration. In addition, the disappearance of the multiple steady states and the change observed at low frequencies in the impedance diagrams prove that the additive modifies the rates of some of the elementary reactions taking place at the interface and seems to decrease the importance of the autocatalytic step in the reaction mechanism.

Journal ArticleDOI
TL;DR: The vitesse de la reduction electrochimique de l'oxygene depend de la concentration des sites actifs superficiels qui varie en fonction des proportions de cuivre ajoutees.
Abstract: L'oxygene peut etre reduit electrochimiquement, en milieu legerement acide (pH=6.6) sur les manganites de cuivre, Cu x Mn3−x O4, de type spinelle. La reduction se fait probablement sur les sites actifs crees par les ions manganese tetravalents, Mn4+, jouant le role d'accepteur des electrons vis a vis du solide et celui de donneur vis a vis des molecules ou atomes d'oxyene adsorbes. La vitesse de la reduction electrochimique de l'oxygene depend de la concentration des sites actifs superficiels qui varie en fonction des proportions de cuivre ajoutees. La nature et la concentration des anions de l'electrolyte support influence la vitesse de reduction.

Journal ArticleDOI
TL;DR: In this article, the effect of gas bubbles generated at an anode on the ionic mass transport rate at the associated cathode was analyzed by means of an experimental laboratory-scale copper electrowinning cell in which the bubbles were (a) permitted to rise freely in the entire cell and (b) restricted in their motion by a copper baffle-plate placed between the two electrodes.
Abstract: The enhancing effect of gas bubbles generated at an anode, on the ionic mass transport rate at the associated cathode is analysed by means of an experimental laboratory-scale copper electrowinning cell in which the bubbles were (a) permitted to rise freely in the entire cell and (b) restricted in their motion by a copper baffle-plate placed between the two electrodes. The improvement in mass transfer observed in the unrestricted case has been correlated via statistical regression analysis to the intensity of bubble motion and pertinent cell parameters.

Journal ArticleDOI
TL;DR: In this article, an electrochemical pump cell has been used to produce Hypobromite and propylene oxide in an electrostatic pump cell and the production rates have been related to the space-time histories of the species within the cell.
Abstract: Hypobromite and propylene oxide have been generated in an electrochemical pump cell and the production rates have been related to the space-time histories of the species within the cell. Production rates are typically 0.15 and 0.11 mol h−1 dm−2 (depending on current density) and energy yields 1.4 and 2.7 kW h kg−1 respectively. Other figures of merit are given.