Current Transients at a Spherical Electrode

Following a potential step to a potential where electron transfer is transport-limited, the diffusion-controlled flux/, as a function of time, to a spherical electrode of radius re is given by 

It follows that the larger the microelectrode, the longer it takes for a steady-state current to be established. For a macroelectrode with re = 1 mm and D = 10 cm s (a typical value), r 1 month Natural convection is likely to influence electrochemical responses after around 20s, so the steady-state regime is never observed for large electrodes. 

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