Marked enhancement of photocatalytic activity and photochemical stability of N-doped TiO2 nanocrystals by Fe3+/Fe2+ surface modification

N-doped TiO2 (N-TiO2) nanocrystals with anatase and Futile mixed phases were prepared by partial oxidation of TiN. The samples were further modified by Fe-ions through incipient wetness impregnation method. The as-prepared samples were characterized by XRD, TEM, XPS, Raman, EPR, UV-vis DRS, and PL in detail. The results indicated that Fe mainly existed as Fe3+/Fe2+ ions on the catalyst surface. The addition of small amounts of Fe-ions to N-TiO2 nanocrystals caused several times enhancement of the photocatalytic activity under visible, UV and UV-vis light irradiation in degradation of gaseous toluene. The optimized Fe-ions content in this investigation was 0.02 wt.%. EPR and PL clearly showed that Fe3+/Fe2+ redox cycle facilitated electron/hole charge separation, and contributed to the enhanced photocatalytic performance. Moreover, the photochemical stability of N-TiO2 nanocrystals under visible light was improved due to the stabilization of nitrogen atoms in TiO2 lattice by surface Fe-ions modification. The N-doped TiO2 nanocrystals without Fe-ions modification Suffered from a gradual deactivation due mainly to the loss of lattice-nitrogen during the photocatalytic reaction. The way to modification of non-metal-doped TiO2 nanomaterials brought new concept in enhancing the photocatalytic performance from the viewpoint of practical application. (c) 2009 Elsevier Inc. All rights reserved.