Visible light-induced degradation of carbon tetrachloride on dye-sensitized TiO2

Abstract

This study investigated an application of TiO2 photocatalyst sensitized with tris(4,4'-dicarboxy-2,2'-bipyridyl)ruthenium(II) complex to CCl4 degradation under visible light;irradiation, By injecting electrons from the photoexcited:sensitizer to the conduction band, the sensitized TiO2 degraded CCl4 under the irradiation of lambda > 420 nm. The quantum yield of CCl4 dechlorination was about 10(-3). The dechlorination rate of CCl4 was reduced in the presence of dissolved O-2 due to its competition for conduction band electrons. The photolysis rate was dependent on pH due to the strong pH dependence of the sensitizer adsorption on TiO2 surface with a maximum degradation rate achieved at pH similar to3. A two-site Langmurian model successfully described the adsorption of the sensitizer on TiO2 particles. The monolayer coverage was achieved at the added sensitizer concentration of 10 muM at [TiO2] = 0.5 g/L. However, the photolysis rate of CCl4 showed a maximum at a sensitizer surface coverage of 0.3 monolayer. Since the photoinduced electron injection gradually depleted active sensitizer molecules an TiO2, sacrificial electron donors to regenerate the sensitizer were sought. 2-Propanol as an electron donor was efficient in the present (RuL3)-L-II/TiO2/CCl4 system, which showed no sign of deceleration in the dechlorination rate up to 6 h of irradiation.