Relations between Tafel and Potential-Decay Slopes

Relations between Tafel and Potential-Decay Slopes 

The adsorption behavior of intermediates is usually related to the difference ofTafel (dV/d logi) and potential relaxation ( — dV/d log t) slopes. In the simple case of potential relaxation of a process that does not involve appreciable coverage by intermediates, namely, 9 0.02, say, as for the HER at Hg, the kinetics of potential relaxation are derived from the following differential equation  

In the more interesting case here where 6 is significant and potential dependent, Qi must be replaced, to an approximation, by Qi + where is the adsorption pseudocapacitance of the chemisorbed intermediate derived from differentiating the (Langmuir) isotherm 

The potential-relaxation kinetics must then be determined from the following equation (for Q Q,)  

Then the logarithmic slope of potential decline in time is 

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Vlll. Relations between Tafel and Potential-Decay Slopes... 

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