Thermodynamic and Kinetic Characteristics of Intermediates
of Electrode Reactions: Determination by Direct and Combined
Electrochemical Methods

A. G. Krivenko^z, A. S. Kotkin, and V. A. Kurmaz

Institute of Problems of Chemical Physics, Russian Academy of Sciences,
Institutskii pr. 16, Chernogolovka, Moscow oblast, 142432 Russia

Received December 29, 2003; in final form, July 1, 2004

Abstract—The potentialities of electrochemical and combined methods for the determination of thermody-
namic characteristics and kinetic parameters of intermediates are analyzed. The electrochemical methods
include polarography, versions of voltammetry, and chronopotentiometry. The combined methods combine
nonelectrochemical (or indirect) generation of intermediates with electrochemical methods of their subsequent
investigation: photomodulation voltammetry, method of polarography of pulsed-radiolysis products, method of
indirect electrolysis, electrochemiluminescence, and a group of laser photoemission methods. Theoretical foun-
dations and basic advantages and disadvantages of the laser photoemission methods (the measurement of pho-
tocurrents in potentiostatic conditions—method of time resolved voltammograms obtained under chopped illumina-
tion and the measurement of the kinetics of variations in the potential of an electrode after illuminating it by a pulsed
laser—in coulostatic conditions) are described in detail. The potentialities of the laser photoemission methods for the
determination of thermodynamic (standard potentials E⁰ of redox pairs /R, standard adsorption free energies) and
kinetic (values of rate constants W⁰ at an equilibrium potential, bulk lifetime of radicals and products of their
reduction R) characteristics of intermediates are demonstrated by studying a trifluoromethyl radical.

Key words: intermediates, laser photoemission, indirect electrolysis, polarography of products of pulsed radioly-
sis, redox potentials, redox constants, trifluoromethyl radical, photomodulation voltammetry, cyclic voltammetry,
electrochemiluminescence, electroreduction

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