Photo-electro-oxidation of alcohols on titanium dioxide thin film electrodes

P. MANDELBAUM; A.E. REGAZZONI; M.A. BLESA; ALDABE BILMES, S

JOURNAL OF PHYSICAL CHEMISTRY B - (Print)

AMER CHEMICAL SOC

Lugar: Washington; Año: 1999 vol. 103 p. 5505 - 5511

1520-6106

The photo-electro-oxidation on titanium dioxide film electrodes of methanol, 2-propanol, and tert-butyl alcohol has been studied by measuring the transient photocurrents observed during the early stages of illumination. Transients and steady-state photocurrents, measured at different applied potentials and methanol concentrations, were compared with model predictions. The numerical solution of the differential equations corresponding to methanol photo-electro-oxidation, as well as the advanced experimental evidence, supports the hypothesis that surface hole trapping as -OH(.) mediates the charge transfer to methanol. Formation of -OH(.) accounts for the high initial photocurrents, its rapid decay being due to recombination. The rate of oxidation of methanol is then determined by the rate of reaction between -OH(.) and CH(3)OH located in the interfacial region. The oxidation of (.)CH(2)OH to CH(2)O, through the injection of an electron into the conduction band (current doubling), gives rise to an increase in photocurrent; steady state values are later attained. As a consequence, a minimum