Depends what your electrode is made out of and what you think is the representative length scale that best answers your questions!  The diffusion limited current can only resolve to lengths > (sqrt(2*D*t).  Area estimates from capacitance are often flaky due to the potential dependence of the capacitance and the near certainty that any faradaic process will affect the double layer structure through adsorption, new phase formation, fouling etc.  In any case, reference values for the expected capacitance per unit area vary by a factor of 2 and typically only apply to single crystal faces in the specific electrolyte solution used to determine them.  That said, the spatial resolution is of the order of the Debye length (maybe 0.4 nm in typical aqueous electrolytes) and and changes (usually decreases) in the hysteresis observed in cyclic voltammetry almost invariably mean electrode fouling or adsorption.

For more reliable estimates of area, with near atomic resolution the charge associated with the hydride adsorption peaks in 0.5 M sulfuric acid is pretty good for platinum.  for gold, the method of choice the the charge passed to reduce the gold (III) oxides also in 0.5 M sulfuric acid.  since you will probably want to do an electrochemical cleaning step anyway, the gfact that you can extract useful characterisation from this step is an added bonus.

It is not unusual to get roughness factors (real: projected macroscopic area) of the order of 1.2 or even 1.4 from new students, even when the electrode looks super flat.  Anything in excess of these values, is usually symptomatic of leaky seals between the electrode and insulating mantle, This is almost impossible to spot any other way and yet is, in my lab at least, the most common mode of electrode failure and one of the reasons we mostly make out own electrodes.

There is a nice summary of electrode areas by Trasatti, published by IUPAC:

Pure & Appl. Chern., Vol. 63, No. 5, pp. 71 1-734, 1991

You can perform cyclic voltammetry for Measuring hydrogen adsorption/desorption in  solution to determine the electrochemically active surface area (ECSA) of Pt.

or you might use the Randles-Sevcik expression of a reversible electrochemical system to determine.electrochemical active surface area of electrode. 

Thanking you professor

Thanking you professor