Experimental Studies of Flow‐Through Porous‐Graphite Chlorine Electrode

Abstract

The kinetics and mass transfer behavior of the chlorine flow‐through graphite electrode have been studied in solution at 25°C. Discharge cathodic polarizations of the chlorine electrode indicate that the limiting current density depends on the flow rate of the electrolyte, in agreement with the analytical solution for flow‐through under limiting current. Furthermore, the limiting current increases significantly after the activation process, due to the increase in the specific surface area of the graphite. Analysis of limiting current data shows that the macro area exposed to flow increases typically from 20 to 35 cm−1 and is accompanied by an increase in permeability. Attempts to measure the exchange current density for chlorine on graphite indicates that different results are obtained for different porous graphites. The apparent exchange current density is 10−3 A/cm2 and on porous graphite and dense graphite, respectively. The true exchange current density on pyrolytic graphite is measured to be . The electrochemical specific area for porous graphite is estimated from the ratio of the exchange current densities of porous and pyrolytic graphite to be 22 cm−1, in good agreement with the macro area exposed to flow.