Gas-Generating Porous Electrodes: Large Ohmic Resistances

Abstract

It is shown how it becomes possible, in gas-generating porous electrodes (GGPE), to construct polarization curves (PC) that encompass also the region of high ohmic resistances up to an ultimate possible overvoltage that is reached at practically complete expulsion of the electrolyte out of the electrode pores near the front surface of the electrode, without restricting oneself, while taking into account ohmic limitations, by not-too-high values of overvoltages. As the true appearance of the dependence of the magnitude of an effective specific ionic electroconductivity of GGPE on the specific features of the structure of its porous space and the degree of occupation of its porous space by the electrolyte and gas is unknown, an attempt is undertaken to evaluate possible values of limiting ohmic limitations, specifically, to take into account the presence of both maximum and minimum ohmic losses. Calculations of PC and some other characteristics of GGPE are conducted using the constants that are close to the constants that take place for the process of formation of chlorine in dimensionally stable anodes. It is discovered that, if one selects a nonoptimum structure of the porous space of the electrode (this means that, with the emergence of gas pores in the electrode, ohmic losses would rapidly increase), then one fails to realize the values of the electrochemical activity of the electrode in excess of a few A cm–2.