Electrocatalytic Oxidation of Dithionite at a Cobalt(II)tetrasulfonated Phthalocyanine and 5,10,15,20‐Tetrakis‐(4‐sulfonatophenyl)porphyrin Cobalt(II) Modified Gold Electrode in Alkaline Solution

Abstract

In this paper it is shown that the charge transfer kinetics of the oxidation of sodium dithionite at a gold electrode in alkaline solution can be increased by modifying this electrode with cobalt(II)tetrasulfonated phthalocyanine, sodium salt (CoTSPc) or 5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrin cobalt(II), tetrasodium salt (CoTSPor). Electrodeposition of these catalysts is discussed as well as the oxidation of sodium dithionite at these immobilized catalysts. Despite an observed acceleration in the charge transfer kinetics, sodium dithionite is still oxidized irreversibly. However, the improvement in kinetics has beneficial consequences in the field of electroanalysis of sodium dithionite. Comparison of the oxidation at bare gold and modified gold electrodes showed that with improved charge transfer kinetics at the modified electrodes a higher sensitivity and selectivity and a much lower detection limit is obtained.

Comparison between the electrocatalytic properties of different metal ion phthalocyanines and porphyrins towards the oxidation of hydroxide

“…The central metal ion of these macrocycles binds one or two axial ligands and undergoes either metal centered, macrocycle centered and/or axial ligand centered redox reactions. The immobilization of these compounds on an electrode surface can lead to modified electrodes with electrocatalytic properties [16]. Transition metal complexes of macrocyclic ligands, including phthalocyanines and porphyrins, have been widely described as catalysts for oxygen reduction [2].…”

Electrochemical and spectroscopic characterization of a gold electrode modified with 3,4′,4″,4‴ copper(II) tetrasulphonated phthalocyanine

“…The electrochemistry of 3,4 0 ,4 00 ,4 000 CuTSPc is different as compared to the behaviour of CoTSPc at a gold electrode especially in the potential range from À1.2 V to 0.6 V [5,6]. Characteristic for the voltammetric behaviour of CoTSPc at gold is the occurrence of a breaking point at which a maximum coverage is reached.…”

“…Soluble sulphonated phthalocyanines have namely shown to be able to form layers on different types of supporting material, including electrodes [5][6][7][8]. Their aromatic ring structure is completely flat which enables the phthalocyanines in the deposited layer to form columnar aggregates, in which p-stacking interactions between the molecules dominate.…”

Non-destructive characterization of CoTSPc electrochemically deposited on gold electrodes by means of synchrotron X-ray microfluorescence

“…They are commonly used in high-tech applications, such as photosensitizers, in optical data storage and chemical gas sensors [1][2][3][4][5]. The use of phthalocyanines has been expanding into other applied fields, e.g., they are frequently used molecules in electrocatalysis [6][7][8]. Their major characteristics are their high thermal and chemical stability, coupled with their extensive redox chemistry.…”