Individual electrode overvoltages

Individual electrode overvoltages may be determined experimentally by measuring the potential of the individual electrodes at a given current den- 

Determination of individual electrode overvoltages and elimination of iR contribution. 

Selected hydrogen overvoltages for various electrode materials in dilute sulphuric acid 

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The overvoltage of an individual electrode may be expressed as the sum of contributions from activation, concentration and resistive film overvoltages... 

Decomposition curve, decomp the minimum potential difference which must be applied between a pair of electrodes before decomposition occurs and a current flows, decomp tittle theoretical signiflcance since it is made up of two individual electrode potentials and their associated overvoltages. 

The power characteristics of a photocell can be constructed from the individual current voltage curves of the photoelectrode and the counter electrode. This is shown in Fig. IV.4, again for an n-type semiconductor. In this figure the influence of the counter electrode is indicated. If the redox reaction there is slow, i.e. if it needs large overvoltages, the power characteristics are very much worsened. A similar effect has the photoelectrode if the photocurrent does not increase very steeply below the open circuit photovoltage and does not reach the saturation current very soon. 

On oxide electrodes or in oxide formation on metal electrodes O atoms or O" radicals certainly play an important role, particularly at high temperatures where the overvoltages become much lower. The kinetics, however, depend in all cases on the individual system, and no general conclusion can be given for the oxygen electrode reaction mechanism except for the role of the chemisorption energy of the intermediates, as outhned in the preceding discussion. 

Step was relatively simple. In addition to the above conditions, a change of the concentration of the ionic species in the film was taken into account by IczKOWSKi [58] and Bennion and Tobias [34]. Finally Iczkowski [63] computed the total current density of the H2 oxidation on porous nickel electrodes as the sum of the currents which would be produced at the given overvoltage by each of the individual pores in 1 cm of electrode material... 

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