Low Anodic Potentials Research Articles

The anodic dissolution of Pb in H 2SO 4

Summary The anodic dissolution of Pb in H2SO4 has been investigated. The Pb dissolves as Pb2+ and PbSO4 ions at low anodic potentials. At higher potentials solid PbSO4 is formed by a solid state reaction. PbSO4 can also be formed by a solution-precipitation mechanism.

The anodic dissolution of Pb in H2SO4

The anodic dissolution of Pb in H2SO4 has been investigated. The Pb dissolves as Pb2+ and PbSO4 ions at low anodic potentials. At higher potentials solid PbSO4 is formed by a solid state reaction. PbSO4 can also be formed by a solution-precipitation mechanism.

Anodic Dissolution of Beryllium in Anhydrous Media

When the residual water content of currently used electropolishing solution is reduced to less than 0.1 g/1, the anodic dissolution of beryllium follows Faraday's law with a valence of one over an extended range of anodic potentials. This result is interpreted in terms of a dissolution mechanism occurring in a succession of two individual steps, each involving a simple electron, thus Support for the transitory existence of the monovalent ions is derived from thermodynamic considerations allied with the structure of the anodic layer. Microscopic examination of the state of the anode surface during and after the dissolution shows clearly that a mechanical disintegration of the metal lattice by the action of the current cannot be the origin of the anomalous valence observed. On the contrary, it is shown that disintegration of this type contributes only at low anodic potentials. This phenomenon, known as the “chunk effect,” is clearly observable by scanning electron microscopy and accounts for faradaic “efficiencies” of greater than 200% in certain electrolytic conditions.

Mechanism of the electrooxidation of methanol on a smooth platinum electrode in alkaline solution

1. The proposed mechanism of the electrooxidation of methanol on a platinum electrode explains the formation of various chemisorbed particles and various products of electrooxidation in alkaline and acid solutions under stationary conditions. 2. In alkaline solution, in contrast to acid solution, a process of catalytic decomposition of methanol, parallel to the electrooxidation of chemisorbed particles, takes place on a platinum electrode at high concentrations of methanol and at low anodic potentials. 3. The apparent activation energy of the electrooxidation of methanol in alkaline solutions is lower than in acid solutions at the same p'otentials.

Theoretical Efficiency of a Thermionic Diode

A theoretical analysis of the efficiency of a thermionic diode is made in the highly efficient region of very low anode potential (Va<1 volt). Maximum efficiency is calculated as a function of the cathode temperature for optimum values of anode potential. The calculations are performed for different values of usuable power density, anode temperature and emissivity of electrodes.

Electrochemical Behavior of Nickel Compounds: II . Anodic Dissolution and Oxygen Reduction in Perchlorate Solutions

The anodic dissolution of Ni, Si, and Sb and of the compounds , , , and was studied in molar perchlorate solutions at pH 0.04 and 10.8. In all cases, except with Si in acid solution, active dissolution at low anodic potentials is followed by a transition to a passive state where the anodic current density is nearly independent of potential. In acid solution, the critical potentials of , , and are less positive than that of Ni and the critical currents are less by two to three orders of magnitude. The critical potential of is about the same as for Sb, but the critical current is substantially less. The anodic current in the passive region for the compounds is greater than for passive Ni. , , and show a transpassive region in which Sb, As, and S are probably oxidized to ions of a high valence state. In alkaline solution, , , and show an active‐passive transition at the same potential as pure Ni. However, the rate of oxidation of these compounds in the passive state is again considerably greater than for passive Ni. It is suggested that in acid solution the passive film on nickel compounds is either a mixed oxide or an oxide having the basic structure of the second element; in alkaline solution, nickel oxide is formed first, but it probably has a different structure than the oxide formed on passive Ni. The difference between acid and alkaline solutions arises from the difference in the stability of nickel oxide in the two electrolytes. A stable, passive oxide on Ni is formed in acid solution only when the dissolution rate is sufficiently large to cause nickel hydroxide to precipitate at the electrode surface, a condition not fulfilled during the dissolution of any of the compounds. In general, the oxide of the companion element or a mixed oxide is more stable than nickel oxide in acid solution at low potentials. This situation is reversed in alkaline solution, and in this case the initial passive film is nickel oxide.The electrocatalytic reduction of oxygen on nickel and nickel compounds occurs in the potential region where a passive film is stable. The order of catalytic activity for oxygen reduction is in acid solution, and in alkaline solution.

銅陽極電位に及ぼす不純物の影響 (第2報)

Effect of Impurities such as arsenic, antimony, bismuth and tin on the copper anode potential has been studied.By the presence of β-Cu3As in anode copper the anode potential is extremely raised, but a large portion of arsenic dissolves in electrolyte to form arsenic or arsenious acid. The raise in potential of antimony containing anode is caused by formation of Sb2O3 (ortho) slime. Bismuth does not dissolve in copper but presents at grain boundaries. Effect of bismuth on anode potential is quite different depending on Cl-ion. The absence of Cl-ion leads to raise in potential according to copper slime formed by the reducing reaction of bismuth. On the contrary, the presence of it brings about the fall in anode potential by means of a formation of bismuth oxychloride slime. Tin forms SnO2 slime, but has no effect on anode potential. When the temperature of electrolyte is low, arsenic, antimony and tin lower anode potentials during the first stage of electrolysis. These phenomena can be explaind as the results of the decrease of activation polarization.

銅陽極電位に及ぼす不純物の影響 (第1報)

Influence of impurities included in copper anode upon the anode potential-time curve has been studied. The anode polarization potential during electrolysis at constant temperature and constant current density was measured against a copper reference electrode. Results for sulfur, lead and oxygen are reported.Sulfur included in copoer anode formsβ-Cu2S anode slime during electrolysis. Anode potential is raised and the time to become the passive state is shortened with increase of sulfure content. Lead forms PbSO4slime and its effect on anode potential is similar to sulfur. Behavior of oxygen is complicated. At low bath temperature anode potential depends on oxygen content, but at high bath temperature influenced other factors such as current density etc.Müller's Bedeckungstheorie may be applied at the present investigation.