Selective production of superoxide ions and hydrogen peroxide over nitrogen- and sulfur-doped TiO2 photocatalysts with visible light in aqueous suspension systems

Superoxide ions (O-2(center dot-)) and hydrogen peroxide (H2O2) produced by visible light irradiation were analyzed to investigate the photocatalytic reaction mechanism for commercially available nitrogen- and sulfur-doped TIO, (BAPW25 and SJC). O-2(center dot-) was detected by the chemiluminescence (CL) probe rnethod with luminol, while the amount of H2O2 was measured as the CL intensity by the reaction with the luminol oxidized upon the addition of hemoglobin. By irradiation with 442-nm light, the S-doped TiO2 surpassed the N-doped TiO2 in the ability to produce O-2(center dot-), while the N-doped TiO2, surpassed the S-doped TiO.) in accumulating H2O2. The difference in the photocatalytic processes was attributed to the multivalence property of sulfur atoms which may promote the decomposition of H2O2.