Selective Production of Superoxide Ions and Hydrogen Peroxide over Nitrogen- and Sulfur-Doped TiO₂Photocatalysts with Visible Light in Aqueous Suspension Systems

Superoxide ions (O 2 •− ) and hydrogen peroxide (H 2 O 2 ) produced by visible light irradiation were analyzed to investigate the photocatalytic reaction mechanism for commercially available nitrogen- and sulfur-doped TiO 2 (BAPW25 and SJC). O 2 •− was detected by the chemiluminescence (CL) probe method with luminol, while the amount of H 2 O 2 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 TiO 2 surpassed the N-doped TiO 2 in the ability to produce O 2 •−, while the N-doped TiO 2 surpassed the S-doped TiO 2 in accumulating H 2 O 2 . The difference in the photocatalytic processes was attributed to the multivalence property of sulfur atoms which may promote the decomposition of H 2 O 2 .