Studies On TiO₂ Photoelectrocatalytic Degradation Of Organic Pollutants And The Action Of TiO₂ Conduction Band Electron

Most of the researchers have paid attention to the photoelectrocatalysis because it can effectively separate the activated hole-electron pairs. At present, most of them only investigated the direct oxidation caused by photo-induced hole while the role of the photo-induced electrons was usually ignored and could not be used to degrade pollutants. In order to testify the O2 reduction caused by photo-induced electrons and promote the efficiency of photocatalysis, we did the following research:O2 and H+ reduction was analyzed by CV and SCV methods. Two redox peaks clearly appeared in the CV and SCV curves. The analytic results indicated that H+ mainly took part in the reaction in acidic condition whereas O2 mainly took part in the reaction in alkaline condition in the first redox peak potential range. In the second reduction peak range, H+ was reduced to H2 in acidic condition whereas the reduction process was mainly induced by Ti4+ in alkaline condition. According to the research on the type of reduction process occurred at the TiO2/Ti electrode, we found that H+ reduction was controlled by diffusion. Furthermore, H2O2 reduction at the TiO2/Ti electrode was analyzed by steady CV method, and the analytic results indicated that H2O2 can be reduced to Free Hydroxyl Radical.A new "double electrode oxidation" photoelectrocatalytic system was composed by using TiO2/Ti electrode as photoanode and cathode respectively. Methylene blue (MB) was used as target pollutant. The MB degradation results indicated that the TiO2 conduction band electrons can reduce O2 to form active oxygen species which has strong oxidation ability. MB can be decomposed by this kind of active oxygen species. Compared to graphite electrode, TiO2/Ti electrode exhibited higher O2 reduction efficiency. Besides, the MB degradation efficiency caused by indirect oxidation at the TiO2/Ti cathode is nearly the same as that of direct oxidation at the TiO2/Ti photoanode.The experiment results showed that in the "Double electrode oxidation" photoelectrocatalytic system, TiO2/Ti electrode can be used as cathode which can take indirect oxidation in the degradation of pollutants。Furthermore, the TiO2 conduction band electrons can reduce dissolved oxygen to active substance was confirmed.