Enhanced photocatalytic activity of TiO2 assisted by Nb, N and S multidopants

• Doping with multiple ions (Nb, N, S) enhances the photocatalytic activity of TiO2.
• In the multi-doped TiO2, S substituted for Ti whereas N substituted for O.
• Multiple doping in TiO2 improves visible light absorption.
• Lifetime of the photogenerated charge carriers is higher in multidoped TiO2.
• Super oxide, hydroxyl radicals and holes are the active species for dye degradation.

A novel visible light active photocatalyst is synthesized by doping TiO2 with multiple dopants like Nb, N and S. TiO2 exists as anatase phase and the particle size is in the range of 10–25 nm. A significant red shift of the absorption edge and increased visible light absorption is shown by multidoped TiO2 compared to undoped TiO2. The tri-doped TiO2 has the highest activity for the photodegradation of methyl orange and the activity shows the order: 0.6NbNS–TiO2 > P25 > 0.6Nb–TiO2 > NS–TiO2 > pristine TiO2. The enhanced photocatalytic activity of tri-doped TiO2 is due to the reduction of band gap and enhancement of lifetime of photogenerated charge carriers. This multidoped catalyst is found to be stable and only a marginal decrease in the activity is observed upto 3 cycles. Experiments with quenchers suggest that all super oxide, hydroxyl radicals and photogenerated holes are active species for the oxidation reaction.

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