Electrochemistry in a Packed-Bed Electrode of Activated Carbon Particles: An Investigation of Faradaic and Capacitive Processes

Abstract

This paper deals with faradaic and capacitive processes occurring in a packed bed electrode of activated carbon particles. On the basis of the anodic oxidation of sulfite/bisulfite ion in a sulfate medium, activated carbon NC 40 was shown to allow a higher conversion rate than graphite particles of comparable external surface area. However current density has to be kept far below the limiting current density to avoid destruction of the brittle material. Besides, capacitive phenomena at the electrode could be described using an overall model. The accessible area and the specific capacitance of the material could be determined from charge/discharge experiments and voltammetric curves: both variables were shown to be increasing functions of the applied potential. The approach developed for modelling the porous electrode is discussed and compared to published models.