Effect of adsorbed uracil and its derivatives on the rate of oxygen reduction on platinum in acid electrolytes

Citation
Hm. Saffarian et al., Effect of adsorbed uracil and its derivatives on the rate of oxygen reduction on platinum in acid electrolytes, J ELEC CHEM, 504(2), 2001, pp. 217-224
Citations number
28
Categorie Soggetti
Spectroscopy /Instrumentation/Analytical Sciences
Journal title
JOURNAL OF ELECTROANALYTICAL CHEMISTRY
ISSN journal
15726657 → ACNP
Volume
504
Issue
2
Year of publication
2001
Pages
217 - 224
Database
ISI
SICI code
Abstract
The rate of oxygen reduction in 0.5 M H2SO4 has been controlled by adsorbin g uracil and its alkyl derivatives on a Pt electrode. Addition of an ethyl group to C(5), or methyl groups to the C(5) and C(6) positions of uracil, e nhances the reaction rate. 5-Ethyluracil and 5,6-dimetfiyluracil have such an effect, however, only when their concentrations in the electrolyte are l ess than or equal to 0.1 mM. Substitution of the hydrogen on N(3) with -CH3 , or exocyclic oxygens with -OCH3 groups results in the inhibition of the r eaction; 1,3-dimethyluracil and 2,4-dimethoxypyrimidine (0.1 mM) are two sy stems that cause inhibition. Interaction between the surface Pt atoms and t he N(3) and O sites on the organic molecule, especially in the presence of -CH3 or -C2H5 groups on the C(5) and/or C(6) centers, are essential for the enhancement. Results of rotating disk electrode experiments suggest that a t low overpotentials, 5-ethyluracil and 5,6-dimethyluracil increase the exc hange current to produce higher reaction rates. (C) 2001 Elsevier Science B .V. All rights reserved.