Current-Time Dependence at Constant Potential Potentiostatic Regime

3 CURRENT-TIME DEPENDENCE AT CONSTANT POTENTIAL (POTENTIOSTATIC REGIME) 

Using a three-electrode systan and a potentiostat, described in Chapter 6, a constant potential can be set up and the current density vs. time can be measured. This organization of measuronents is called the potentiostatic regime. 

If there is no convection. Equation 7.8 can be used with only the first term on the right-hand side. Under these conditions and when the potential is held constant, the current measurements can be used to define (1) the Nemst diffusion layer thickness, 5n, as a function of time and (2) the diffusion coefficient of the electrochemically active species. In the potentiostatic regime, the concentration of the electrochemi-caUy active species is a function of both distance from electrode, x, and time, t. Let us see how the equation for Pick s second law 

Equation 7.10 can be solved with the following initial and boundary conditions  

D is the effective diffusion coefficient of a binary electrolyte as defined earlier 

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