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 CH3OH located in the interfacial region. The
oxidation of •CH2OH to CH2O, 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
transient is observed. The minimum is marginally observable in tert-butyl alcohol solutions, in line with the
properties of the respective radicals.