Behavior of Hydrophilic Porous Oxygen Electrodes with Silver Electrocatalyst

Abstract

An experimental study of the behavior of porous hydrophilic oxygen electrodes shows the important influence of the electrochemical reaction on the shape of the i-E curves at low current densities. A correlation between mass transport properties of the electrolyte, x/SD• and the slope of the polarization curve is found at medium current densities. Convection appears to be important at high current densities. The depth of the effective reaction zone has been calculated under varying conditions.

The Effect of Liquid Configuration in Porous Gas Electrodes

“…No matter which way the pressure is being changed, the drop in activity after passing the maximum is steeper than the rise in activity on approach to the maximum. This type of behavior has been previously reported for porous hydrogen electrodes (2), and, more recently, for porous oxygen electrodes (5,6,16). The nature of the response of electrode activity to changes in differential pressure clearly indicates that it is associated with the penetration of liquid into pores and its expulsion from them.…”

“…In addition ionic current transport must proceed along electrolyte paths on these walls. For conditions where little or no electrolyte is present in the gas electrode except in the form of thin films it has been found that the performance is scarcely affected by changes in differential pressure and that predictions of overpotential behavior based on a simple film mechanism are quite adequate (6,14). However, when considerable additional electrolyte is present in the pores, performance deviates considerably from such predictions, and the influence of liquid configuration assumes great importance.…”

“…The performance of a porous gas electrode is dependent not only on its pore structure but also on the configuration of the gas-liquid interfaces within the pores. Thus the differential pressure established across an electrode has been found by many investigations to be an important influence (1)(2)(3)(4)(5)(6)(7). Explanations presented for differential pressure effects have been based almost entirely on the distribution between gas and liquid filled pores that is found in electrodes with wide ranges of pore size distribution (2,8,9).…”

A Method for Characterizing the Structure of Hydrophilic Porous Gas Diffusion Electrodes

“…The film resistance measurements were carried out by means of a special probe, see Fig. [14]. The main probe body was made of PMMA.…”

“…and compared it with data from nickel electrodes operating on oxygen in 80% KOH. LindstrSm (13) and Lindholm et al (14) correlated the electrochemical activity with the electrolyte film resistance. LindstrSm (13) and Lindholm et al (14) correlated the electrochemical activity with the electrolyte film resistance.…”