Effect of N-doping on the photocatalytic activity of sol-gel TiO2

► Mechanism of N-doping on the visible light photocatalytic activity of TiO2 has been investigated. ► The effect of increasing temperature on the nature of the band gap is investigated. ► The N-doped titania samples prepared at 500 °C showed the highest amount of photocatalytic activity compared to the control TiO2 and Degussa P25. ► The interaction between nitrogen dopant sources and titania precursors during sol-gel synthesis is studied. ► The anatase-to-rutile transition is mainly dependant on the nature of the dopant precursors employed.