Effect of N-doping on visible light activity of TiO2–SiO2 mixed oxide photocatalysts

• Effect of hydrazine was studied on the visible light activity of TiO2–SiO2.
• Silica presence increased the thermal stability of anatase phase to 600 °C.
• Use of hydrazine resulted in nitrogen doping and oxygen vacancy creation.
• TiSi-6N exhibited surface area 260 m2/g and visible light absorption up to 520 nm.
• TiSi-6N reduced Se(VI) into Se(0) within 90 min of visible light radiation.

The present report deals with the effect of nitrogen doping on TiO2–SiO2 mixed oxide photocatalysts. Advantageous effect of mixing SiO2 with TiO2 and subsequent N doping on the visible light photocatalysis is discussed. Hydrazine is used as the nitrogen doping source. Mixed Oxide to hydrazine ratio is varied from 1:2 to 1:8 to study the hydrazine concentration effect on the surface and photocatalytic properties. Presence of silica increases the surface area and thermal stability of anatase phase whereas nitrogen doping enhances the visible light absorption. Presence of substitutional nitrogen and oxygen vacancy in TiO2 lattice is due to the use of hydrazine which is also a reducing agent. Material prepared with 1:6 hydrazine ratio (TiSi-6N) shows surface area of 260 m2/g and light absorption up to 520 nm. Under visible light only TiSi-6N is able to completely reduce Se(VI) into its elemental form within 90 min of reaction.