Photocatalytic activity of N-doped and N-F co-doped TiO2 and reduction of chromium(VI) in aqueous solution: An EPR study

? N-doped and N-F co-doped TiO2 catalysts were characterized by EPR spectroscopy. ? Nb and O2- radicals were formed in N- and N-F TiO2 and Ti3+ in N-F TiO2 catalysts. ? Electron capturing by O2 and generation of O2- was favored for N-doped catalyst. ? Cr(VI) reduction depends on the Nb quantity, crystal size, conduction band energy. ? TNF1 (Ti:N/F molar ratio of 1:1) showed higher photocatalytic reduction of Cr(VI).