Oxidation of hydrogen peroxide at the dropping mercury electrode

1984 ◽  
Vol 49 (10) ◽  
pp. 2320-2331 ◽  
Author(s):  
Miroslav Březina ◽  
Martin Wedell
Keyword(s):  
Hydrogen Peroxide ◽  
Superoxide Anion ◽  
Ph Value ◽  
Mercury Electrode ◽  
Electrode Process ◽  
Electrochemical Processes ◽  
Dropping Mercury Electrode ◽  
Oxidation Of Hydrogen ◽  
Decreasing Ph ◽  
Rate Controlling Step

Reduction of oxygen and oxidation of hydrogen peroxide at the dropping mercury electrode are electrochemical processes strongly influenced both by the pH value and the anions in solution. With decreasing pH, both processes become irreversible, especially in the presence of anions with a negative φ2 potential of the diffusion part of the double layer. In the case of irreversible oxygen reduction, the concept that the rate-controlling step of the electrode process is the acceptance of the first electron with the formation of the superoxide anion, O2-, was substantiated. Oxidation of hydrogen peroxide becomes irreversible at a lower pH value than the reduction of oxygen. The slowest, i.e. rate-controlling step of the electrode process in borate buffers at pH 9-10 is the transfer of the second electron, i.e. oxidation of superoxide to oxygen.

A NOTE ON THE POLAROGRAPHIC ANALYSIS OF HYDROGEN PEROXIDE

1948 ◽  
Vol 26b (12) ◽  
pp. 767-772
Author(s):  
Paul A. Giguère ◽  
J. B. Jaillet
Keyword(s):  
Hydrogen Peroxide ◽  
Mercury Electrode ◽  
Limiting Current ◽  
Diffusion Current ◽  
Polarographic Analysis ◽  
Dropping Mercury Electrode ◽  
Strychnine Sulphate

The determination of hydrogen peroxide at concentrations higher than those normally covered in polarography was studied with various electrodes. The diffusion current was found to increase linearly with the peroxide concentration up to 0.15% with the dropping mercury electrode and up to nearly 1% with a fixed platinum microelectrode. Under these conditions the limiting current was about 10 times greater than that usually observed. Although the solutions were supersaturated with oxygen, traces of strychnine sulphate were sufficient to suppress all maxima.

Electrochemical Investigations of the Nickel(II)-Penicillamine System. 3. A Study of the Catalytic Hydrogen Prewave in Connection with Structure of Nickel(II)-Penicillamine Complexes

2000 ◽  
Vol 65 (6) ◽  
pp. 995-1013 ◽  
Author(s):  
Florinel G. Banica ◽  
Ana Ion
Keyword(s):  
Redox Reactions ◽  
Mercury Electrode ◽  
Proton Donor ◽  
Electrode Process ◽  
Nickel Ion ◽  
Acid Component ◽  
Hydronium Ion ◽  
Dropping Mercury Electrode ◽  
Catalytic Hydrogen ◽  
Catalytic Hydrogen Evolution

The catalytic hydrogen evolution on the dropping mercury electrode in the presence of Ni(II) and D-penicillamine (Pen) at pH around 6 yields a catalytic hydrogen prewave (CHP) with E1/2 = -1.21 V vs SCE. This wave is similar to the CHP produced by selenocysteine and cysteine described previously. The occurrence of the CHP depends on the formation of the mono(D-penicillamine-N,S)nickel(II) complex whereas bis(D-penicillamine-N,S)nickel(II) complex is inert and has no influence on the CHP electrode process. Although the analogous bis(cysteine) complex is labile, there is strong evidence that it does not take part directly in the CHP process in the Ni(II)-cysteine system. The actual proton donor in the CHP electrode process is the hydronium ion and not the acid component of the buffer. A tentative reaction mechanism was formulated with emphasis on the state of the intermediate hydrogen species. The characteristic pH, nickel ion involvement and the structure of the ligand make the CHP process an attractive model for hydrogen redox reactions catalyzed by [NiFe] hydrogenase.

scholarly journals Reduction of Cd(II) Ions in the Presence of Tetraethylammonium Cations. Adsorption Effect on the Electrode Process

Electrochem ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 415-426
Author(s):  
Juan Torrent-Burgués
Keyword(s):  
Mercury Electrode ◽  
Reduction Process ◽  
Inhibitory Effect ◽  
Electrode Process ◽  
Adsorption Effect ◽  
A Value ◽  
Half Wave ◽  
Dropping Mercury Electrode ◽  
Electrode Coverage ◽  
Isotherm Equations

The effect of the adsorption of tetraethylammonium (TEA) cations, which present both ionic and organic characteristics, on the reduction of Cd(II) ions have been studied from dc and ac measurements at the dropping mercury electrode. The resistance to the charge transfer (Rct) and Warburg coefficient (σ) parameters have been determined through impedance measurements. Thus, the global velocity constant has been obtained. The reduction process of Cd(II) in perchloric media is reversible and is affected by the adsorption of TEA cations, especially at high TEA concentrations. Values of E1/2, half wave potential, and DO, diffusion coefficient, obtained from both dc and ac measurements agree. The velocity constants show a decrease as TEA concentration increases, with values ranging from 0.6 to 0.01 cm·s−1. The inhibitory effect of TEA adsorption on the electrode process and the relationship between electrode coverage, θ, and velocity constants, K, using several isotherm equations, have been discussed. The best fit was obtained with the equation K = 0K(1 − θ)a with an a value close to three, indicating a blocking effect and electrostatic repulsion due to TEA.

Electrochemical Investigations of the Nickel(II)-Penicillamine System. 2. Direct Identification of Complex Species Involved in Catalytic Nickel Reduction on the Dropping Mercury Electrode

1998 ◽  
Vol 63 (7) ◽  
pp. 995-1006 ◽  
Author(s):  
Florinel G. Banica ◽  
Ana Ion
Keyword(s):  
Mercury Electrode ◽  
Formation Constants ◽  
Active Species ◽  
Electrode Process ◽  
Ligand Complex ◽  
Direct Identification ◽  
Complex Species ◽  
Nickel Ions ◽  
Dropping Mercury Electrode ◽  
System 2

The catalytic polarographic nickel prewave was investigated by making appropriate correlations between prewave current and complex species concentrations as calculated by means of available formation constants. It was concluded that the active species is (D-penicillaminato-N,S)nickel(II) [NiL], whereas the bis-ligand complex, [NiL2]2-, is inert and does not play any role in the electrode process. The catalytic character of the electrode process originates from the regeneration of [NiL] by the reaction of adsorbed ligand molecules with free nickel ions available in the bulk of the solution. Conversely, all the complex species in the Ni2+-cysteine system are labile. Consequently, the reaction mechanism in this case may include the dissociation of the complex [NiL2]2- as an alternative path for the generation of the active species, [NiL]. The bell-shaped form of the prewave was interpreted in terms of potential-dependent catalyst adsorption.

An interface reaction of Hexavalent chromium: The polarographic behaviour of HCrO4- and CrO42-

1955 ◽  
Vol 8 (1) ◽  
pp. 51 ◽  
Author(s):  
JH Green ◽  
A Walkey
Keyword(s):  
Ph Value ◽  
Mercury Electrode ◽  
Interface Reaction ◽  
Proton Donor ◽  
Interface Reactions ◽  
Inorganic Systems ◽  
Trivalent State ◽  
Current Voltage ◽  
Dropping Mercury Electrode ◽  
Adsorption Desorption

Current-voltage relationships have been determined for the electroreduction of dilute chromate solutions in a range of bicarbonate-carbonate buffers at the dropping mercury electrode. Double waves are obtained whose relative heights are a function of the pH value. By analogy with the behaviour of pyruvic acid an interface reaction with some proton donor prior to the reduction to the trivalent state is suggested (CrO42- +HB- → HCrO4- + B-). The rate constants for the interface reaction are computed for different donors by the method of Koutecky and Brdicka (1947). Adsorption-desorption processes in the region of the electrocapillary zero may account for the shape of the current-voltage curves, and, if so, the explanation based simply on an interface reaction will require modification. The occurrence of interface reactions and of adsorption-desorption processes in other inorganic systems is discussed.

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