Phosphorus and boron codoping into TiO₂ nanoparticles; an avenue for enhancing the visible light photocatalytic activity

TiO₂ nanoparticles codoped with phosphorus and boron (P,B-TiO₂), having visible light activity were prepared by sol–gel method. As prepared samples were calcined at different temperatures and the obtained samples were characterized by different techniques. XRD analysis reveals that the codoping decreases the particle size and retards the phase transition by increasing the thermal stability. The absorption edge of the P,B co-doped samples exhibit redshift as evidenced by the UV–visible absorption spectra. From XPS measurements, it is clear that the doped boron and phosphorus substitutes the oxygen and titanium sites respectively. Visible light driven MB degradation by these phosphorus and boron codoped samples is much better than that of photocatalytic activity of only P doped TiO₂, and commercially available Degussa P25. The P,B-TiO₂ sample heated at different temperatures exhibits enhanced charge separation as evidenced by the low temperature EPR studies with in situ visible light irradiation (>400 nm) which inturn is responsible for the enhanced photocatalytic activity.