INVESTIGADORES
ALDABE Sara Alfonsina
artículos
Título:
THE INFLUENCE OF APPLIED BIAS POTENTIAL ON THE PHOTOOXIDATION OF METHANOL AND SALICYLATE ON TITANIUM DIOXIDE FILMS
Autor/es:
P. MANDELBAUM; ALDABE BILMES, S; A.E. REGAZZONI; M.A. BLESA
Revista:
SOLAR ENERGY
Editorial:
PERGAMON-ELSEVIER SCIENCE LTD
Referencias:
Lugar: Amsterdam; Año: 1999 vol. 65 p. 75 - 80
ISSN:
0038-092X
Resumen:
The mechanism of the photoelectrochemical oxidation of methanol and
salicylic acid on anatase film electrodes was studied as a function of
the applied potential and pollutant concentration at pH 3. The
dependencies of the steady state photocurrents on substrate
concentration reflect the type of surface interaction: weak in the case
of methanol, that leads to a simple saturation curve, and strong in the
case of salicylate, that shows a steady state photocurrent peaking at
intermediate concentrations. At 0.6 V vs. SCE the oxidation rate is
largely enhanced as compared to open circuit conditions (Eoc=−0.3
V). Even under nitrogen, the reaction proceeds at an appreciable rate,
and the ratio of circulated charge to the number of oxidized salicylate
ions approaches 28 electrons per mol at low salicylate concentration:
oxidized salicylate mineralizes almost totally, and the intermediates
are rapidly destroyed. At higher substrate concentrations, the ratio
decreases, and uv spectral evidence suggests the formation of some
undefined oxidation products. Under oxygen at 0.6 V, the radicals
generated in the initial photoelectrochemical step are mostly oxidized
by O2, increasing the amount of salicylate destroyed for a
given total circulated charge; at sufficiently high substrate
concentration, the above ratio decreases to values below 4. No evidence
of the presence of traces of partially oxidized molecules is found.
Adequate control of the experimental conditions permits therefore to
achieve substantially increased efficiencies of salicylate destruction
per absorbed photon, and the build up of uncontrolled intermediates can
be prevented. The results are discussed in terms of the oxidation length
Y, defined as the number of oxidation steps that are triggered by a single hole transfer event, and of the oxidation efficiency ϵ,
defined as the ratio of the oxidation length to the maximum possible
oxidation length (the length achieved when one hole transfer suffices to
trigger total mineralization).