Determination of dissolved oxygen by catalytic reduction on Nafion-methyl viologen chemically modified electrode.
A small size Nafion-methyl viologen chemically modified electrode (Nafion-MV CME) together with a small size electrolytic cell were constructed for the purpose of dissolved oxygen (DO) determination. The catalytic reduction of DO on Nafion-MV CME results in fast and sensitive DO determination. The mechanism of such detection is also considered.
Electrocatalytic reduction of oxygen by poly(viologen)-poly (sulfonate) complex coated on graphite electrodes
Le potentiel de demi-vague de la reduction d'O 2 est independant du pH et sa valeur est de −0,40 V (vs e.c.s.). Les electrodes de graphite recouvertes de methylviologene fortement incorpore dans un film de sulfonate et avec le complexe intermoleculaire de poly(xylylviologene) et de polysulfonate ont un fort effet catalytique sur la reduction d'O 2
Oxidative electrochemistry of electropolymerized metalloprotoporphyrin films
Abstract The course of electrochemical oxidation has been monitored by cyclic voltammetry, ring-disk voltammetry, and absorption spectroscopy for metalloporphyrin electrode films prepared by electropolymerization of Zn II and Fe III protoporphyrin IX (PP) complexes. In CH 2 Cl 2 both films show stable cyclic voltammograms (CV's) over the first oxidation wave, assigned to porphyrin radical cation formation. Addition of 2% H 2 O to the electrolyte is without effect on the first oxidation of Zn II PP, but contact with aqueous buffer (pH 6.9) enhances the anodic current six-fold, decreases the cathodic current and abolishes subsequent electroactivity; the inactivated film contains modified porphyrin species, as shown by its absorption spectrum on SnO 2 . It is suggested that oxidation proceeds via nucleophilic attack of H 2 O on the Zn II PP + radical cations, leading eventually to the six-electron product dioxoporphomethene. The same product is indicated for the Fe III PP film which also shows a six-fold anodic current enhancement in contact with aqueous buffer, and subsequent inactivation. But in this case a large negative shift in the anodic peak potential suggests (Fe IV =0)PP formation, and the inactivation pathway is suggested to involve O atom transfer to the porphyrin rings. For the Fe III PP film 2% H 2 O already produces a significant negative shift and broadening of the anodic peak, and a decrease in the cathodic current. Ring-disk voltammetry demonstrates some O 2 production accompanying oxidation of the Fe III PP film, but not the Zn II PP film, in contact with aqueous buffer; the yield accounts for only 2% of the oxidation current. Addition of (ClPh) 3 P, intended to intercept the O atoms of the (Fe IV =O)PP units, results only in accelerated film inactivated, probably via a radical process.