T. Ohno et al., Vanishing of current-doubling effect in photooxidation of 2-propanol on TiO2 in solutions containing Fe(III) ions, J PHYS CH B, 104(29), 2000, pp. 6801-6803
When organic compounds such as 2-propanol are in aqueous solutions and are
photooxidized on the surface of semiconductor electrodes, the current quant
um efficiency can reach close to 200% (current-doubling effect). However, w
e found that the current-doubling effect in the photooxidation of 2-propano
l on TiO2 electrodes disappeared in solutions containing Fe(III) ions. From
the analyses of the products, we found that acetone was produced in quanti
tative correlation to the photocurrent, and that practically no Fe(II) ions
were generated in the solution. We also found that Fe(IT) ions were not ox
idized at a TiO2 photoanode in a solution containing Fe(III) ions, while th
ey were oxidized in quantitative correlation to the photocurrent in the sol
ution without Fe(III) ions. These results refuted the possibility that Fe(I
II) ions accepted electrons from the oxidation intermediates of 2-propanol.
The plausible reason for the disappearance of the current-doubling effect
is that 2-propanol is oxidized by two holes on the Fe(III)-adsorbed TiO2 su
rface.