Diffusion open-circuit-decay transients

Fig. 7K Charge injection followed by open-circuit decay (the coulostatic method). Diffusion limitation (low values of /x ) slows down the decay transient, as expected from the equivalent circuit shown in Fig. 2K.

As described, the alternative method for the deduction of radical kinetics is the use of ESR transient signals [65, 66]. Transient signals are obtained by open-circuiting an electrode which was previously at a potential corresponding to the diffusion-limited current. The electrode is open circuited by opening a switch, rather than stepping the potential between two defined values since the latter method may produce contributions to the radical decay from, e.g. re-oxidation of a radical anion, if the latter is generated by... 

We shall treat here the simplest case, in which the pulse duration is very short compared to the time constant for charging the double-layer capacitance, (tp/Xc < l) and diffusion limitation can be ignored. Under such conditions, no Faradaic reaction takes place during the charging pulse. Once on open circuit, the capacitor will be discharged through the Faradaic resistor, It is easy to derive the form of the decay transient. On the one hand, the current is given by ... 

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