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The Nature of the Anodic Films Formed on Platinum Electrodes in the Presence of 1‐Naphthol
Author(s) -
Babai M.,
Gottesfeld S.,
Gileadi E.
Publication year - 1979
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.197900013
Subject(s) - chemistry , electrochemistry , platinum , microporous material , adsorption , inorganic chemistry , electron transfer , monolayer , diffusion , anode , sulfuric acid , molecule , electrode , photochemistry , organic chemistry , catalysis , biochemistry , physics , thermodynamics
The adsorption and electrochemical surface reactions of 1‐naphthol on platinum in 0.5 M sulfuric acid were investigated by optical and electrochemical methods. At low anodic potentials (up to 0.65 V vs. dhe) monolayer adsorption of the organic molecule was observed with a significant extent of charge transfer. At more anodic potentials electrochemical polymerization occurs with films reaching several hundred Angstroms in thickness. Film growth is halted if the potential is decreased below 0.65 V. A parabolic rate of growth is observed and is attributed to slow, rate determining migration of electrons from the film/solution interface to the metal via the π electron systems of the polymeric film. At higher anodic potentials (above ca. 1.00 V) the parabolic growth law is no longer followed due to the occurrence of side reactions. The polymeric film is microporous, allowing passage of water molecules and ions at a low rate (low diffusion coefficient in the film). As a result the rate of electrochemical reactions on the film‐covered surface is diffusion controlled and depends mainly on bulk concentration, resulting with an apparent selectivity with respect to oxidation or reduction of the solvent.