Computational and Experimental Study of the Cyclic Voltammetry Response of Partially Blocked Electrodes. Part 1. Nonoverlapping, Uniformly Distributed Blocking Systems

Abstract

The cyclic voltammetry response of partially blocked electrodes is modeled using finite difference simulations and a method presented for determining currents at electrode surfaces which have a well-defined geometric blocking pattern. Peak current and peak separation data are presented for six decades of scan rates, blocking coverage values between 0.1 and 0.9 and between the limits of reversible and irreversible electrochemistry. The validity of the simulation approach employed is verified by data obtained experimentally from purpose-built partially blocked gold film electrodes, with either a cubic or hexagonal geometric array of electroinactive disks uniformly distributed on the electrode surface. Comparison of theory with experiment suggests that the modeling of hexagonally distributed blocking systems is superior to that of the cubically arranged ones.

Electrochemical Characterization of Polyelectrolyte/Gold Nanoparticle Multilayers Self-Assembled on Gold Electrodes

“…The CMM 27,28 considers that the electrode coverage is not complete in the early stages of growth of the multilayer and describes it as an array of circular areas that are uncovered by both PE and NPs and, therefore, more accessible to the electroactive species. [37][38][39][40][41][42][43] These uncovered areas may persist during the sequential assembly of the multilayer, although they are progressively reduced in area and number as more layers are added. These areas play a key role in the transport properties of the multilayer, even after they are completely covered, because the film is less dense in those regions where there were opened spots previously and the flux density of the electroactive species is higher.…”

“…Mass transport in this model accounts for the possible defects present in the multilayer leading to nonlinear diffusion. [37][38][39][40][41][42][43] There is substantial experimental evidence on the existence of defects and preferential paths for diffusion at the first stages in the growth of PEMUs. 44,45 We also demonstrate here the existence of defects in the early and intermediate stages of the build-up process of PE/Au NP multilayers by means of the AFM technique, thus supporting the validity of the CMM.…”

Diffusion regimes at nanoelectrode ensembles in different ionic liquids

“…NEEs can be considered as partially blocked electrodes [18,[21][22][23], being composed by a very large number of very small ultramicroelectrodes, all statistically equivalent since their large number make border effects negligible [24,25]. From a general viewpoint, arrays of micro and nanoelectrodes can exhibit distinct voltammetric response regimes depending on the thickness of the diffusion layer and distance between the nanoelectrode elements [16,18,[22][23][24][25].…”

“…From a general viewpoint, arrays of micro and nanoelectrodes can exhibit distinct voltammetric response regimes depending on the thickness of the diffusion layer and distance between the nanoelectrode elements [16,18,[22][23][24][25]. Three distinct limit cases can be achieved: (A) total overlap (TO) regime: when radial diffusion boundary layers overlap totally (hemi-distance between nanoelectrodes smaller than radius of diffusion hemispheres); (B) pure radial (PR): when the nanoelectrodes behave independently (hemi-distance between nanoelectrodes larger than radius of diffusion hemispheres); (C) linear active (LA): when the nanoelectrodes behave as isolated planar electrodes, each under semi-infinite linear diffusion.…”

“…Under these conditions partial overlap of diffusion layers occurs. Theoretical models have been developed for ordered [22,[25][26][27] and random [28] arrays of electrodes.…”