Silver Electrocrystallization onto Carbon Electrodes with Different Surface Morphology:  Active Sites vs Surface Features

Abstract

The influence of the electrode surface quality and surface morphology on the silver electrocrystallization process onto a carbon substrate from 10 -2 M Ag(NH 3 ) 2 + /1.6 M NH 3 , 1 M KNO 3 (pH ) 11) electrolyte solution was studied. Three substrates with different types of surface morphology and surface roughness were used: highly oriented pyrolitic graphite (HOPG), mechanically polished vitreous carbon (MPVC), and fractured vitreous carbon (FVC). Before the silver deposition process, the electrode surface was examined and characterized by means of Atomic Force Microscopy (AFM) analysis. Evaluation of the kinetic parameters of the silver nucleation and the growth behavior, as well as other characteristics of the silver electrocrystallization process onto carbon substrates, were based on cyclic voltammetry and chronoamperometric measurements. Cyclic voltammetry data also show that silver deposition efficiency is proportional to the increase of electrode surface roughness (from HOPG, via MPVC to FVC). The silver bulk deposition process on all three carbon substrates was characterized as 3D nucleation and diffusion-controlled growth. However, this process proceeds with different overpotentials on different substrates: the lowest for HOPG and the highest for MPVC electrode surface. The major electrocrystallization parameters, such as nucleation rate, number of active sites, and number of formed silver nuclei, strictly related to the electrode surface conditions, seem to not follow the same trends as the cyclic voltammetry data. It is clearly indicated in the nonlinear relationship between number of active sites and the surface features (recognized in AFM images). As pointed out in the discussion, it opens new questions regarding the nature of the active sites for deposition on the electrode surface and their identification by microscopic techniques.

Electrodeposition of bismuth onto glassy carbon electrodes from nitrate solutions

“…With the increase of deposition potential, the current transient curve approaches closer the limit for 3D instantaneous nucleation and growth. Such a potential dependence also occurred in the electrodeposition of copper on Au(1 1 1) [57], silver on different carbon substrates [58], and bismuth on fluorine-doped tin oxidecoated conducting glass substrates [44]. Fig.…”

An electrodeposition study of the nucleation and growth of silver on boron-doped diamond electrodes

“…The deposition of silver on to carbon electrodes has been extensively studied on glassy carbon macroelectrodes [6,7] as well as highly ordered pyrolytic graphite (HOPG) surfaces [8,9] and carbon fibre microelectrodes [10][11][12]. Particularly, silver is a popular system when investigating fundamental aspects of nucleation theory as its deposition has been shown to be under diffusion control (at concentrations and potentials similar to those studied in this paper) [13][14][15].…”

Cavity microelectrodes for the voltammetric investigation of electrocatalysts: the electroreduction of volatile organic halides on micro-sized silver powders

“…the halide leaving group, the structure of the organic moiety, the solvent and the supporting electrolyte). In particular, the electrocatalytic activity of silver was reported to increase with increasing surface roughness [15,16], thus prompting the research toward the development of micro-and nano-sized electrode materials, whose properties usually encompass the simple geometric effect on the real surface area. New investigation methodologies have to be developed, which allow easy separation between the different contributions of the disperse electrocatalytic material and its immobilizing system.…”