Cadmium Electrode Research Articles

The dissolution of iron from the negative material in pocket plate nickel-cadmium batteries

A common mode of failure of nickel-cadmium flooded pocket plate cells is iron poisoning of the positive plate due to transfer of iron into the active material from active materials and materials of construction. Nickel plated steel pockets are sometimes used to minimize iron dissolution, particularly on the positive electrode. Sometimesα-Fe2O3 is used as an additive to the cadmium electrode. This paper assesses the extent of dissolution of iron fromα-Fe2O3 by using electron microscopy, X-ray crystallography, cyclic voltammetry, coulometric and atomic absorption measurements.

Nickel-Cadmium Batteries as Capacitive Filters for Pulsed Loads

This investigation consisted of several tests of specially fabricated nickel-cadmium batteries having circular disk-type electrodes. These batteries were evaluated as filter elements between a constant current power supply and a 5 Hz pulsed load demanding approximately twice the power supply current during the load on a portion of the cycle. Short tests lasting 104 cycles were conducted at up to a 21 C rate and an equivalent energy density of over 40 J/Ib. In addition, two batteries were subjected to 10h dischar cycles, one at a 6.5 C rate and the other at a 13 C rate. Assuming an electrode-to-battery weight ratio of 0.5, these tests represent an energy density of about 7 and 14 J/Ib, respectively. Energy density, efficiency, capacitance, average voltage, and available capacity were tracked during these tests. After 10y capacity degradation was negligible for one battery and about 20 percent for the other. Cadmium electrode failure may be the factor limiting lifetime at extremely low depth of discharge cycling. The output was examined and a simple equivalent circuit was proposed.

Effect of an organic additive on the impedance of cadmium in alkaline solution

The a.c. impedance of a planar cadmium electrode in KOH solution was measured over the active and passive region using a potentiostatic technique. Different concentrations of polyvinyl alcohol (PVA) were subsequently introduced into the alkaline solution and the impedance remeasured. It was found that the addition of PVA markedly increased the double layer capacity of the electrode and decreased electrolyte resistance,R sol. The impedance spectra in the presence of PVA were analysed in terms of an equivalent circuit involving the series combination of two double layer capacitances and a resistance proportional to the conductivity of the electrolyte.

Response of Copper(II) and Cadmium(II) Ion-selective Electrodes in Some Nonaqueous Solvents

Abstract The response of cadmium(II) and copper(II) ion-selective electrodes was evaluated in methanol, ethanol, acetonitrile solutions and their mixtures with water. The electrodes showed an almost Nernstian behavior in nonaqueous solutions and their mixtures with water except in acetonitrile.

Ideally rechargeable cadmium electrodes for alkaline storage batteries

Cd/Cd(OH)2 electrodes based on sintered nickel substrate have been developed which show a stabilized capacity-utilisation of 96±2% pf the theoretical value even at the end of fifty cycles of deep discharge at ambient temperatures. Simultaneously, the extent of cadmium migration into the separator on extended cycling or storage has been found to be practically negligible. These improvements have been realized by the incorporation of an alkali-stable colloidal surfactant into the electrode during its fabrication so that both the crystal growth and migration of cadmium hydroxide are suppressed by a protective-colloid action of the surfactant.

Ignition of lean methane-air mixtures by high pressure glow and ARC discharges

Glow and arc discharges have been used to study the spark-ignition of lean quiescent methane-air mixtures at room temperature and a pressure of p =2 bar. The regions of stable long-duration sparks with aluminum, cadmium, copper, platinum and tungsten electrodes as well as the fall voltages and voltage gradients of the positive column have been determined. For both discharge modes the minimum ignition energies and the corresponding quenching distance have been obtained for Cu electrodes at equivalence ratios of 0.59, 0.67 and 0.77. Minimum ignition energies for various electrode materials have been measured at the quenching distance and an equivalence ratio of =0.67. The experimental results indicate that the energy dissipated in the anode and cathode fall is completely lost to the electrodes, whereas the energy of the positive column determines the flame initiation process. These findings are substantiated by spark-flashlight schlieren photographs of the incipient spark and flame kernel.

Electrochemical synthesis of 2,2,6,6-tetramethylpiperidine

A preparative method for the production of 2,2,6,6-tetramethylpiperidine based on the electrochemical reduction of 4-oxo-2,2,6,6-tetramethylpiperidine in 30% sulfuric acid on cadmium or lead electrodes was developed.

Demetallization and the specific anion adsorption effects in the electrodeposition of cadmium from acidic solutions

The anion effects observed by Abd El-Halim et al. in the electrodeposition of cadmium from acidic baths were quantitatively analysed in terms of our previous theory of the effect of anions on the potentials of zero charge of demetallized surfaces. It is argued that the specifically adsorbed anions form a surface compound on the cadmium surface, thus leading to its demetallization. The parameter b characteristic of the interactions involved between the cadmium electrode and the anions was evaluated and correlated with the deposition potential observed in the baths containing the corresponding anions. It was further shown that the trends in the shifts to more negative deposition potentials tend to be associated with the corresponding expected shifts of the potential of zero charge for the various anions under examination. It is concluded that specific adsorption of anions can provide a theoretical framework for understanding the role of anions in the electrodeposition of cadmium.

Reactivity of Scratched Cadmium Electrodes in Alkaline Solutions

The kinetics of reaction of scratched cadmium electrodes in alkaline solution have been measured. The anodic reaction rate of the freshly generated metal surface follows Tafel's law with a slope and a reaction order . The equilibrium parameters are defined by (NHE) and . The parameters are interpreted in terms of simultaneous transfer of two electrons per cadmium atom oxidized from the bare metal surface.

On the anomalous behaviour of deeply discharged, sealed NiCd cells

Some sealed NiCd cells on a deep, constant-current discharge show anomalous behaviour in that their voltage remains (after polarity reversal) i the range from −6O to −260 mV. This situation can sometimes persist for an unlimited time without any increase in the overpressure in the cell or of its voltage. A necessary condition for the appearance of this discharge voltage level is a discharge capacity reserve of the cadmium electrode and the presence of cadmium in the separator as a result of its migration from the negative to the positive electrode. The cadmium particles form bridges across the separator leading eventually to a short circuit, whereby the electrode reactions in the cell cease. This concept was substantiated by using separators impregnated with Cd(OH) 2.

Application of EMF-pH Diagrams to Corrosion Prediction

Abstract EMF-pH diagrams calculated from physical property data can be practical tools to air in corrosion prediction. The EMF-pH diagrams of two practical systems relating to actual process corrosion problems are examined. These are titanium in a concentrated HCl-NaCl solution containing an organic component modeled as aspartic acid, and a cadmium electrode in the presence of dissolved EDTA. Procedures for estimating the needed thermodynamic properties are discussed in detail. Both examples show that placement on these diagrams of the pH and the measured corrosion potential provide a useful way to relate the theoretical thermodynamic diagram to the real world. By coupling the EMF-pH diagram with these properly determined properties, useful insights are gained so reasonable hypotheses can be established and appropriate further experiments can be run.

The hydrogen evolution reaction on pocketed porous cadmium electrodes

The hydrogen evolution reaction on porous cadmium (containing iron and carbon) confined in a perforated pocket of nickel-plated steel was studied under commercially relevant conditions in lithiated KOH. The results show how the relatively slow reaction on cadmium is influenced by the electrode structure and the admixed expander and powder lubricant. These additional materials promote the hydrogen reaction possibly by a synergistic mechanism.

Plastic-bonded electrodes for nickel—cadmium accumulators. VIII. Study of oxygen recombination rate on plastic-bonded cadmium electrodes provided with active carbon catalyst

The oxygen recombination (reduction) rate on plastic-bonded cadmium electrodes in sealed NiCd systems can be controlled by the use of a catalytic mix consisting of active carbon and carbon black either in the pure state or mixed with PTFE. This catalytic mix is either rolled onto the gas side of the plastic-bonded cadmium electrode or added to the active material prior to the preparation of the electrode by a rolling technique. The highest oxygen recombination rate, which surpassed that obtained with commercial pocket-type electrodes, was obtained in both cases by the use of an active carbon, carbon black and PTFE catalytic mix. In this case an optimum three-phase boundary, well known from oxygen electrodes for fuel cells, was established.

Detection of cadmium electrode surfaces using cw and pulsed radiation

Simultaneous in situ photoacoustic, photoconductive, and electrochemical detection of species at the surface of the cadmium electrode has been demonstrated using both cw and pulsed light sources. The advantages of the cw and pulsed photoacoustic techniques were evaluated. Both techniques were applied to study the passivation of the cadmium electrode on high rate discharge. Cadmium oxide was identified on the electrode after passivation.

Plastic-bonded electrodes for nickel-cadmium accumulators: IX. Oxygen recombination rate on plastic-bonded cadmium electrodes with different active materials

The rate of oxygen recombination ( i.e., reduction) on plastic-bonded cadmium electrodes in sealed NiCd systems can be controlled over a wide range by doping the negative active material with Ni(OH) 2, Fe 3O 4 or carbon black. The highest recombination rate was attained by combining all these additives (treatment of CdO with Ni(OH) 2 and subsequent addition of Fe 3O 4 and carbon black), allowing the plastic-bonded electrodes obtained to be used without further modifications in sealed NiCd systems.

ChemInform Abstract: THE EFFECT OF IRON(III) ON THE CADMIUM ION‐SELECTIVE ELECTRODE

AbstractFe(III) stört den Betrieb von Cd‐, Pb‐ oder Cu‐Ionen‐selektiven Elektroden.

Electrocatalysis of the reduction of nitrate ion at cadmium electrodes by electrodeposited copper

The irreversible reduction of nitrate to nitrite at a cadmium electrode in slightly alkaline solution is electrocatalyzed by copper deposited on the electrode surface. Mass transport-limited currents were observed at a Cu—Cd disc electrode to rotational velocities of 1050 rad s -1 (10000 rev. min -1). Electron mugraphs revealed that the copper is plated as closely packed muspheres less than 1 μm in diameter.

A chromatographic determination of nitrate with amperometric detection at a copperized cadmium electrode

A copperized cadmium flow-through electrode is applied for cathodic detection of nitrate in the effluent stream of a liquid chromatograph. The nitrate is separated from dissolved oxygen in a small (10 cm) column of strong-base, anion-exchange resin (Dowex 1-X8) with 5 mM perchloric acid as the eluent. The effluent stream is buffered to pH 8 by mixing with a stream of buffer prior to detection. A large excess of chloride added to the sample dramatically improves the separation of nitrate from dissolved oxygen in the sample.

The Effect of Iron(III) on the Cadmium Ion-selective Electrode

Abstract Iron(III) interferes with the operation of a cadmium, lead and copper ion-selective electrode. The cadmium ion-selective electrode (CdS/Ag2S) showed a potential shift to the positive direction of more than 100 mV for a decade change of iron(III) concentration. However, the exact mechanism for this interference is not known, though it is expected to be the oxidation of sulfide ion by Fe(III). The mechanism of interference by iron(III) was studied by using the cadmium ion-selective electrode, flow-through cell, pH buffer solutions, potentiometric titrations, and atomic absorption spectrophotometry measurements. It was found that iron(III) promotes dissolution reaction of cadmium ions from the solid cadmium sulfide electrode and that flow conditions of samples have no effect on the iron(III) interference.

Cadmium in alkaline solution

This review is intended to up-date the literature which has appeared since the previous article by Armstronget al. [1] concerning the behaviour of the cadmium electrode in alkaline solution. In general the early literature will not be discussed since this is adequately covered elsewhere [2–7]. The wider aspects of the electrochemical behaviour of cadmium in various electrolytes can be found in the extensive review by Hampson and Latham [6].