Species involved in transport

Throughout this chapter, we shall specifically exclude electrode reactions that consume or generate insoluble species. Thus, the most general electrode reaction is 

Cases in which one of the reactants or products is the material of the electrode itself, as in 

There is, of course, always an ample supply of the electrolytic solvent (often water) and of the electrode material (often a metal) at the 

Usually, there is no significant impediment to the transport of electrons, through this may not be true of some semiconductor electrodes [2—7], When there is more than one reactant, it is usually possible to adjust bulk concentrations (or adopt other experimental strategies such as buffering) so that all reactants except one are in such excess that their transport poses no difficulty. This is an analog of the isolation technique familiar to kineticists. The same is true of product species it is generally possible to arrange experimental conditions so that, at most, only one product species is subject to a transport restriction. 

we shall customarily ignore all but one reactant species and all but one product species. Moreover, we shall assume that the stoichiometric coefficients of these species are both unity. This is not an essential 

---