Enhanced visible light photocatalytic activity of Ga, N and S codoped TiO2 for degradation of azo dye

• Doping with multiple ions (Ga, N, S) enhances the photocatalytic activity of TiO2.
• In the multi-doped TiO2, S substituted for Ti whereas N substituted for O.
• Enhanced absorption of visible light is observed for multidoped-TiO2.
• Lifetime of the photogenerated charge carriers is higher in the doped samples.
• Superoxide and hydroxyl radicals are major active species involved in MO photodegradation.

We report an enhanced, visible light, photocatalytic activity for TiO2 doped with multiple dopants like Ga, N and S. The pristine and doped TiO2 nanoparticles exist as anatase phase of TiO2 having a particle size of 12–15 nm. Improved visible light absorption is seen for N, S and Ga, N, S tri-doped TiO2 and the highest visible light absorption is observed for GaNS–TiO2. XPS analysis shows the presence of bonded S and N (N–Ti–O, S–Ti–O) in the sample. Photocatalytic activity of the samples of TiO2 were evaluated for the degradation of methyl orange (MO) in visible light and GaNS–TiO2 exhibits the highest activity. The enhanced activity of GaNS–TiO2 is attributed to a combination of factors like creation of defect level within the bandgap of TiO2, enhanced lifetime of photogenerated charge carriers and increased photoresponse. Addition of quenchers like benzoquinone (BQ) and 2-propanol results in the 21% and 17% decrease in photodegradation of MO indicating that the O2−·O2−· and OH are the predominant active species in the visible light, photodegradation of MO, using GaNS–TiO2.

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