In order to evaluate the photoelectrochemical activity of
Ti/TiO2 electrode and to confirm its ability for photoelectrocatalysis
oxidation of formaldehyde, we performed cyclic voltammetry
experiments in the dark and under UV light irradiation in theabsence and presence of formaldehyde (Fig. 4). The tests were
conducted in phosphate buffer solution (pH 7.0). As can be seen in
Fig. 4, electrochemical oxidation current value of Ti/TiO2 electrode
in dark and in the absence of formaldehyde is very small (curve a).
However, value of this current under irradiation increases very
much (curve c). This indicates that photogenerated electrons on
Ti/TiO2 electrode could be effectively driven to the counter
electrode by applied positive potential, which would be beneficial
to electron–hole separation. Using the same conditions, we
studied the photoelectrochemical behavior of Ti/TiO2 electrode
in the presence of formaldehyde (curves b and d). In dark, almost
no difference between currents were observed in the absence and
presence of formaldehyde which means that no electrochemical
oxidation of formaldehyde at the surface of Ti/TiO2 electrode
occurred. But under UV illumination, a significant increase was
showed in the presence of formaldehyde with respect to the
absence of this material. The cause of these observations is that in
buffer solution, the photogenerated holes in Ti/TiO2 electrode
oxidize either adsorbed water molecules or hydroxyl groups,
while the presence of formaldehyde provides a much more facile
pathway for the transfer of holes across the film/electrolyte
interface, which results in the higher photocurrent.
Hydrodynamic amperometry was used to study the photoelectrochemical
response of Ti/TiO2 electrode, in buffer solution
in the absence and presence formaldehyde with two various
concentrations under UV irradiation