For a rotating disk electrode operating at sufficiently great potential, the redox reaction rate is governed by the rate at which analyte diffuses through the diffusion layer to the electrode (Figure 17-15b). The thickness of the diffusion layer is
whereis the diffusion coefficient of reactant is the kinematic viscosity of the liquid
and is the rotation rate (radians/s) of the electrode. There are radians in a circle. The current densityis localid="1655441451764" is
localid="1655441445229"
where nis the number of electrons in the half-reaction, Fis the Faraday constant, and localid="1655441459070" is the concentration of the electroactive species in bulk solution localid="1655441466748" Consider the oxidation oflocalid="1655441474339" in a solution of localid="1655441479067" at +0.90V(versus S.C.E.) at a rotation speed oflocalid="1655441490849" role="math" revolutions per minute. 27The diffusion coefficient oflocalid="1655441497131" and the kinematic viscosity islocalid="1655441503345" Calculate the thickness of the diffusion layer and the current density. If you are careful, the current density should look like the value in Figure 17-16b.
