Photocatalytic degradation Of C2H2 by nitrogen-doped TiO2 (N-TiO2), nitrogen and carbon-doped TiO2 (NC-TiO2), BA-PW25 (commercialized as oxygen deficient TiO2 (TiO2-delta) photocatalyst), and P25 (conventional TiO2) were analyzed. Only BA-PW25 photocatalyst decomposed C2H2 into CO2 under visible light (lambda > 400 nm), while the other photocatalysts did not change C2H2. From the analyses of the byproduct formation and the reaction rate Of C2H2 degradation, it is inferred that the active species effective for C2H2 degradation were formed on the mid-gap level of BA-PW25 at the potentials between the valence-band top of conventional TiO2 and the N-induced mid-gap level of N-TiO2. (C) 2008 Published by Elsevier B.V.