Impact of Adsorption on Scanning Electrochemical Microscopy Voltammetry and Implications for Nanogap Measurements

Abstract

(2016) Impact of adsorption on scanning electrochemical microscopy voltammetry and implications for nanogap measurements. Analytical Chemistry, 88 (6). pp. 3272-3280. Permanent WRAP URL:

Recessed Nanoelectrodes for Nanogap Voltammetry

“…This effect may be significant, despite a relatively large tip radius, because of the very high diffusion flux density at the disk edge . Another factor not included in the theoretical treatment is the recently suggested possibility of adsorption and surface diffusion of FcTMA + on HOPG or on the negatively charged glass surface. A strange feature in experimental nanogap voltammograms is a hysteresis in the current plateau region.…”

Double layer effects in voltammetric measurements with scanning electrochemical microscopy (SECM)

“…The purpose of this paper is to consider the impact of surface charge on scanning electrochemical microscopy (SECM) measurements when configured to create a dual-working electrode thin layer electrochemical cell for kinetic measurements. SECM has found considerable use in characterising fast heterogeneous electron transfer [21][22][23][24], homogeneous (solution) kinetics [25][26][27], detecting adsorbed species [28][29][30] and measuring lateral charge transfer [31][32][33][34][35], amongst a wide range of applications. In many of these studies, the gap between the tip and substrate has usually been at the micron or larger scale and, with the excess supporting electrolyte concentrations used, EDL effects are negligible, because the EDL size is very small compared to the gap size (which defines the concentration boundary layer between the two working electrodes).…”

“…However, recent technical advances have enabled SECM gaps as small as a few 10's of nm to be realised between a parallel dual-working electrode arrangement (so-called "nanogap-SECM") [36,37], which provides ultrafast diffusion rates of redox species between the two working electrodes as seen in other nanogap devices [15,38,39]. In principle, this is highly advantageous for the study of fast kinetics, but the high surface area to solution volume ratio of such devices magnifies certain physicochemical effects, including adsorption [30,40] and, as we show herein, EDL phenomena. EDL effects have been explored very recently for dual-electrode nanogap devices [15,16], and for SECM [17] but in the latter case with the focus on the active part of the tip and substrate electrodes and for the highly charged Fe(CN)6 4-/3couple.…”

Intermittent‐contact Scanning Electrochemical Microscopy (IC‐SECM) as a Quantitative Probe of Defects in Single Crystal Boron Doped Diamond Electrodes

“…The tip was held at 0 V to convert FcTMA 2 + back to FcTMA + at a diffusion-controlled rate. The IC-SECM imaging measurements were carried out at a constant tip-substrate separation of 0.54 mm, as estimated by setting the tip and substrate potentials to promote pure diffusion-controlled feedback between the tip and surface and measuring the tip current compared to the steadystate current of the tip in bulk solution [14,15,29].…”

“…In both cases, and particularly for reaction rate imaging with SECM, knowledge of the tip-substrate separation is essential. As the tip current response depends on both the tip-substrate separation and electrode kinetics at the tip and surface [15], several non-electrochemical methods have been implemented to determine when a tip comes just into contact with a surface. For example, the pioneerAbstract: We demonstrate, for the first time, the use of electrochemical imaging to identify defect and defect free areas in single crystal boron doped diamond (BDD) electrodes.…”