Visible light-sensitive yellow TiO2−xNx and Fe–N co-doped Ti1−yFeyO2−xNx anatase photocatalysts

Nitrogen substituted yellow colored anatase TiO2−xNx and Fe–N co-doped Ti1−yFeyO2−xNx have been easily synthesized by novel hydrazine method. White anatase TiO2−δ and N/Fe–N-doped samples are semiconducting and the presence of ESR signals at g ∼1.994–2.0025 supports the oxygen vacancy and g∼4.3 indicates Fe3+ in the lattice. TiO2−xNx has higher conductivity than TiO2−x and Fe/Fe–N-doped anatase and the UV absorption edge of white TiO2−x extends in the visible region in N, Fe and Fe–N co-doped TiO2, which show, respectively, two band gaps at ∼3.25/2.63, ∼3.31/2.44 and 2.8/2.44 eV. An activation energy of ∼1.8 eV is observed in Arrhenius log resistivity vs. 1/T plots for all samples. All TiO2 and Fe-doped TiO2 show low 2-propanol photodegradation activity but have significant NO photodestruction capability, both in UV and visible regions, while standard Degussa P-25 is incapable in destroying NO in the visible region The mid-gap levels that these N and Fe–N-doped TiO2 consist may cause this discrepancy in their photocatalytic activities.