Combination of Scanning Electron Microscopy in the Characterization of a Nanometer-Sized Electrode and Current Fluctuation Observed at a Nanometer-Sized Electrode

To what extent the effective radius of a nanometer-sized electrode matches its geometric radius is a concern because it is believed that the continuum assumptions of the Nernst-Planck equation do not work when the diameter of the electrode is less than 100 nm. In our research, high-resolution scanning electron microscopy images have been employed to characterize the electrodes whose effective radii have been obtained from electrochemical methods. Thus, electrode geometric and effective dimensions could be compared. Our results show that the geometric radius matches the effective radius very well when the effective radius is larger than 20 nm. There is a significant difference between the effective and the geometric electrode radii when the effective electrode radius is smaller than 20 nm. Current fluctuation can be observed on a 1.6 nm radius electrode at slow scan rates. Possible reasons for the current fluctuation on the electrode are discussed.