ELECTROCHEMICALLY ASSISTED PHOTOCATALYSIS .2. THE ROLE OF OXYGEN AND REACTION INTERMEDIATES IN THE DEGRADATION OF 4-CHLOROPHENOL ON IMMOBILIZED TIO2 PARTICULATE FILMS

The electrochemically-assisted photocatalytic degradation of 4-chlorop henol (4-CP) using immobilized TiO2 particulate films has been investi gated by analyzing reaction intermediates under a variety of experimen tal conditions. The degradations were carried out in both nitrogen- an d oxygen-saturated solutions to explore the role of reduced oxygen spe cies and molecular oxygen in the formation of reaction intermediates a nd in the mineralization of 4-CP. The degradation rate can be greatly improved even in a nitrogen-saturated atmosphere by applying an anodic bias to the TiO2 film electrodes. 4-Chlorocatechol (4-CC) is the pred ominant intermediate observed in oxygen-saturated solutions, whereas h ydroquinone (HQ) is the primary intermediate in nitrogen-saturated sol utions. Molecular oxygen plays an important role in the enhancement of the electrochemically assisted photocatalytic decay rate of 4-CP and the subsequent degradation of reaction intermediates, viz., 4-CC and H Q.