Voltammetry at a single nano-electrode by varying electrode diameters: Review

• Published in: Journal of electroanalytical chemistry (Lausanne, Switzerland) Vol. 779; pp. 7 - 17
• Main Author: Aoki, Koichi Jeremiah
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.10.2016; Elsevier Science Ltd
• Subjects: Acetonitrile; Alternating current; Charge transfer; Coated electrodes; Deformation effects; Diffusion; Disks; Electrodes; Electrolytes; Formation of multi-valent ions without supporting electrolyte; Heterogeneous rate constants; Memory effects of diffusion; Nano-electrodes; Nanostructured materials; Platinum; Rate constants; Reaction kinetics; Species diffusion; Steady state; Voltammetry; Nano-electrodes; Memory effects of diffusion; Formation of multi-valent ions without supporting electrolyte; Heterogeneous rate constants
• ISSN: 1572-6657; 1873-2569
• DOI: 10.1016/j.jelechem.2016.03.029

Steady-state voltammetric responses at a single nanometer-sized electrode are reviewed, in the light of 1) the basic properties of Saito's (diffusion-controlled) Eq. (2)) the heterogeneous charge transfer reaction kinetics, 3) reactions of non-charged redox species without supporting electrolyte, and 4) a limitation of diffusion equations. These data are supported by more than 100 fabricated electrodes, of which diameters range from 1nm to 10μm. Inlaid disk-electrodes are fabricated by polishing a glass-coated platinum wire with a help of the time-variation of ac-current. The four subjects are specified as follows. 1) Small sizing yields the high current density, which is related with scan rates of cyclic voltammetry and the ac-frequency. Effects of deformed disks on the current are discussed. 2) Heterogeneous rate constants for six redox species are attempted to be determined from the variations of their potential shift with a decrease in the diameters. No potential shift is found although fast scan voltammetry exhibits potential shift. The disagreement is discussed from the view of the double layer capacitance. 3) Sigmoidal voltammograms for non-charged redox species are obtained without adding salt in acetonitrile solution when electrode diameters are less than 400nm. Di-anion of the redox species is not generated without salt. 4) Electrodes of which diameters are less than 4μm exhibit the steady-state diffusion-controlled currents less than those calculated from Saito's equation. Simple diffusion is not valid at nano-meter electrodes. Distributions of concentrations (c) and current density (j) at an inlaid disk electrode. [Display omitted] •Heterogeneous rate constants by steady-state currents are too large to be evaluated.•Di-anions of the redox species are not generated without salt.•Saito's equation is valid for diameters larger than 4μm, owing to the memory effects.