Effect of charge transport in electrode-confined N,N'-dialkyl-4,4'-bipyridinium polymers on the current-potential response for mediated, outer-sphere electron-transfer reactions

Journal Article · Thu May 10 04:00:00 EDT 1984 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j150654a017· OSTI ID:6696044

Lewis, N S; Wrighton, M S

Mediated outer-sphere redox processes have been examined at rotating disk Pt/(PQ/sup 2+/+/)/sub n/)/sub surf/ electrodes. The ((PQ/sup 2+/+/)/sub n/)/sub surf/ is a redox polymer anchored to the surface and is formed from N,N'-bis((trimethoxysilyl)propyl)-4,4'-bipyridinium, I. The polymer coverages for the electrodes selected for study are sufficiently great that Fe(phen)/sub 3//sup 3+/2+,E /sup 0/' = + 1.03 V vs. SCE, shows no electrochemical response near its E/sup 0/'. The mediated reduction of Fe(phen)/sub 3//sup 3 +/ and a number of other outer-sphere oxidants is mass-transport limited when the Pt/((PQ/sup 2+/+)/sub n/)/sub surf/ electrode is held approx. 100 mV more negative than E/sup 0/'((PQ/sup 2+/+)/sub n/)/sub surf/ = -0.45 V vs. SCE in CH/sub 3/CN/0.1 M (n-Bu/sub 1/N)ClO/sub 4/. However, contrary to theoretical expectations based only on the rate constant for reaction of Fe(phen)/sub 3//sup 3 +/ with a surface PQ/sup +/, the onset of current for the mediated reduction is at the onset for ((PQ/sup 2 +/)/sub n/)/sub surf/ ..-->.. ((PQ/sup +/)/sub n/)/sub surf/ reduction; in fact, the mediated reduction current in the onset region is directly proportional to the concentration of PQ/sup +/ in the surface-confined polymer. Data for Pt/((PQ/sup 2 +/ xFe(CN)/sub 6//sup 3-/4-/)/sub n/)/sub surf/ electrodes show directly that charge transport in the polymer can be a limitation to the maximum steady-state mediation current in aqueous electrolyte solution at the coverages of ((PQ/sup 2+/+)/sub n/)/sub surf/ that have been employed. The charge-transport properties of the polymer are concluded to control the current-potential profile, as has been reported previously for other surface-modified electrodes, for the large polymer coverages employed in these studies. 26 references, 13 figures, 1 table.

• Research Organization: Massachusetts Inst. of Tech., Cambridge
• OSTI ID: 6696044
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 88:10; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301 -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
400400* -- Electrochemistry
AROMATICS
AZAARENES
AZINES
BIPYRIDINES
CATALYSTS
CATALYTIC EFFECTS
CHEMICAL COATING
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
DATA
DEPOSITION
ELECTROCATALYSTS
ELECTROCHEMISTRY
ELECTRODES
ELECTRON TRANSFER
ELEMENTS
EXPERIMENTAL DATA
HETEROCYCLIC COMPOUNDS
INFORMATION
IRON COMPLEXES
METALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC POLYMERS
PHENANTHROLINES
PLATINUM
PLATINUM METALS
POLYMERS
PYRIDINES
QUANTITY RATIO
REDUCTION
SILICON COMPOUNDS
SURFACE COATING
TRANSITION ELEMENT COMPLEXES
TRANSITION ELEMENTS
VOLTAMETRY