Kinetics of anion transfer across the liquid | liquid interface of a thin organic film modified electrode, studied by means of square-wave voltammetry
Résumé
The electrochemical oxidation of lutetium bis(tetra-tert- butylphthalocyaninato) (LBPC) and decamethylferrocene (DMFC), as well as the reduction of LBPC, lutetium bis(phthalocyaninato) (LPC), and lutetium (tetra-tert-butylphthalocyaninato hexadecachlorphthalocyaninato) (LB-PCl), has been studied in a thin nitrobenzene (NB) film deposited on the surface of a graphite electrode (GE) by means of square-wave voltammetry (SWV). The organic film-modified electrode was immersed in an aqueous (W) electrolyte solution and used in a conventional three-electrode configuration. When the aqueous phase contains ClO4-, NO3-, or Cl - (ClO4-, or NO3- only, in the case of DMFC), both LBPC and DMFC are oxidized to stable monovalent cations in the organic phase. The electron transfer at the GE | NB interface is accompanied by a simultaneous anion transfer across the W | NB interface to preserve the electroneutrality of the organic phase. LBPC, LPC, and LBPCl are reduced to stable monovalent anions accompanied by expulsion of the anion of the electrolyte from the organic into the aqueous phase. In all cases, the overall electrochemical process comprises simultaneous electron and ion transfer across two separate interfaces. Under conditions of SWV, the overall electrochemical process is quasireversible, exhibiting a well-formed "quasireversible maximum" that is an intrinsic property of electrode reactions occurring in a limiting diffusion space. For all the redox compounds that have been studied, the kinetics of the overall electrochemical process is controlled by the rate of the ion transfer across the liquid | liquid interface. Based on the quasireversible maximum, a novel and simple methodology for measuring the rate of ion transfer across the liquid liquid interface is proposed. A theoretical background explaining the role of the ion-transfer kinetics on the overall electrochemical process at the thin organic film modified electrode under conditions of SWV is presented. Comparing the positions of the theoretical and experimental quasireversible maximums, the kinetics of ClO4 -, NO3-, and Cl- across the W | NB interface was estimated. The kinetics of the overall process at the thin organic film modified electrode, represented by the second-order standard rate constant, is 91 ± 8, 90 ± 4, and 133 ± 10 cm4 s-1 mol-1, for the transfer of ClO4 -, NO3-, and Cl- respectively. © 2005 American Chemical Society.
Mots clés
covalent bond
diffusion coefficient
electricity
electrochemistry
electrode
electron transport
film
immersion
ion transport
liquid
molecular interaction
oxidation kinetics
oxidation reduction reaction
phase transition
potentiometry
reduction kinetics
square wave voltammetry
standard
Anions
Electrodes
Equipment Design
Graphite
Kinetics
Lutetium
Nitrobenzenes
Oxidation-Reduction
Surface Properties
Anion transfer
Aqueous phase
Electron transfer
Liquid interface
Diffusion in liquids
Electrochemical electrodes
Electrolytes
Electron transitions
Lutetium compounds
Oxidation
Positive ions
Rate constants
Redox reactions
Thin films
anion
carbene
cation
chlorate
cyanic acid
decamethylferrocene
decane
electrolyte
ferrocene
nitrate
nitrobenzene
organic compound
unclassified drug
analytic method
aqueous solution
article
chemical modification