A novel composite electrode which has the functions of synthesizing H_2O_2 and photocatalysis is reported. This double function composite electrode was prepared by loading photocatalytic TiO_2/C on a novel substrate which can synthesize H_2O_2. In a photoreactor, the composite electrode was used as cathode, a Ru-Ti electrode as anode, a lower pressure Hg lamp as light source. Combining effect of oxidation of photochemistry and photocatalysis exists at the same interface of electrode-solution. The photocatalytic reaction took place on the surface of the TiO_2/C, meanwhile H_2O_2 was produced at the gas- liquid-solid interfaces of the substrate. Current efficiency attained a value of 82% (J = 15 mA/cm~2), and the potential of reduction of O_2 by 2e made TiO_2 gaining about +0.5 V anodic bias (vs. flatband potential) which is very important to improve the photocatalytic activity of TiO_2. The experimental results show that the composite electrode plays an important role in enhancing the oxidation rate of the azo dye molecules. It was found that the oxidation rate of the azo dye molecules is related to its adsorption amount on the surface of composite electrode. Also, the principle of action of the composite electrode and oxidation degradation process of the azo dye molecules were discussed.

Key words: ELECTRODE, TITANIUM DIOXIDE, PHOTOCATALYSIS, DEGRADATION, AZO DYES, ADSORPTION