Non-blocking metal electrodes - one mobile charge in the

2 Non-blocking metal electrodes - one mobile charge in the electrolyte 

The interface structure for non-blocking interfaces is similar to that for related blocking interfaces. Thus the distribution of charge at the C/ Ag4Rbl5 interface will be similar to that at the Ag/Ag4Rbl5 interface. The major difference is that there is one particular interfacial potential difference f at which the silver electrode is in equilibrium with Ag ions in the bulk electrolyte phase. At this value of A, there is a particular charge on the electrolyte balanced by an equal and opposite charge — on the metal. At any potential different from value of q different 

One of the major concerns which we have in relation to non-blocking electrodes is to understand the way in which the current crossing the interface varies with the overpotential tj defined as  

In order to determine the net current flowing, i, as a function of q (and in some cases time) it is generally necessary to work with three or four electrode cells where the electrode of interest (the working electrode) carries current into the cell and a second electrode (the auxiliary or subsidiary electrode) carries the current out of the cell. The third electrode is the reference electrode although in cases where one of the phases is not a metal a second reference electrode is required (four electrode cell). 

The reference electrode(s) carries no net current and has a charged species in equilibrium between it and the electrolyte. The schematic form of such an arrangement is shown in Fig. 10.9 where the reference electrode is a silver wire inserted into Ag4Rbl5 which is, in turn, between two silver sheets which constitute the working and subsidiary electrodes. 

---