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Microelectrode studies of chemical reactions

Microelectrode studies of chemical reactions
Microelectrode studies of chemical reactions
Neumann's integral theorem has been used to establish exact analytical solutions for chronoamperometric experiments and for the steady state limiting current for CE and catalytic EC mechanisms. To convert these solutions into a useful form, FORTRAN programs have been written for the necessary numerical calculations. The analytical response of microdiscs, for chronoamperometry as well as the steady state for CE and EC' reactions is presented. A different theoretical approach, as well as digital simulations, are used for the interpretation of steady state limiting currents for EC' reactions, in particular, silver(II)-substrate coupled reactions. The radius dependence of the ratio between the kinetically and the diffusion controlled currents has been calculated for various kinetic schemes. The anodic oxidations of Cr(III), water and of Mn(II) in the presence of catalytic quantities of Ag(I), were investigated using Pt microdiscs with radii between 0.3 and 62.5 m. Because of the enhanced rate of diffusion to microelectrodes, kinetic currents are observed for the Ag(I) mediated oxidation of Cr(III). It is shown that there is good agreement between the experimental i_k/i_d= f(a) plots and those computed assuming a mechanism where the rate determining step is electron transfer from Cr(III) to Ag(II). The rate constant was determined as 9x10^6 mol^-1 cm^3 s^-1. The Ag(II)-Mn(II) reaction must be substantially faster since in most conditions the measured current is determined by the diffusion of Mn(II) to the surface. As expected but in complete contrast, the Ag(II) water reaction is too slow to observe kinetic currents at microelectrodes.

Denuault, Guy
5c76e69f-e04e-4be5-83c5-e729887ffd4e
Denuault, Guy
5c76e69f-e04e-4be5-83c5-e729887ffd4e

Denuault, Guy (1989) Microelectrode studies of chemical reactions. University of Southampton, Chemistry, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Neumann's integral theorem has been used to establish exact analytical solutions for chronoamperometric experiments and for the steady state limiting current for CE and catalytic EC mechanisms. To convert these solutions into a useful form, FORTRAN programs have been written for the necessary numerical calculations. The analytical response of microdiscs, for chronoamperometry as well as the steady state for CE and EC' reactions is presented. A different theoretical approach, as well as digital simulations, are used for the interpretation of steady state limiting currents for EC' reactions, in particular, silver(II)-substrate coupled reactions. The radius dependence of the ratio between the kinetically and the diffusion controlled currents has been calculated for various kinetic schemes. The anodic oxidations of Cr(III), water and of Mn(II) in the presence of catalytic quantities of Ag(I), were investigated using Pt microdiscs with radii between 0.3 and 62.5 m. Because of the enhanced rate of diffusion to microelectrodes, kinetic currents are observed for the Ag(I) mediated oxidation of Cr(III). It is shown that there is good agreement between the experimental i_k/i_d= f(a) plots and those computed assuming a mechanism where the rate determining step is electron transfer from Cr(III) to Ag(II). The rate constant was determined as 9x10^6 mol^-1 cm^3 s^-1. The Ag(II)-Mn(II) reaction must be substantially faster since in most conditions the measured current is determined by the diffusion of Mn(II) to the surface. As expected but in complete contrast, the Ag(II) water reaction is too slow to observe kinetic currents at microelectrodes.

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More information

Published date: 1989
Organisations: University of Southampton, Chemistry

Identifiers

Local EPrints ID: 179323
URI: http://eprints.soton.ac.uk/id/eprint/179323
PURE UUID: 3a20a301-4588-4ec2-a458-f8dc3ebe8542
ORCID for Guy Denuault: ORCID iD orcid.org/0000-0002-8630-9492

Catalogue record

Date deposited: 08 Jul 2013 10:09
Last modified: 30 Jan 2020 01:26

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