Phosphorus-doped titania nanotubes with enhanced photocatalytic activity

Titania nanostructures have gained much attention lately due to their high specific surface area, ion-exchange ability, and better electrical properties. In this study, pure titania nanotubes (TNTs) were synthesized using hydrothermal method. Phosphorus-doped titania nanotubes (P-TNTs) were fabricated following a wet chemical procedure with dimethyl phosphite as a precursor. Characterization of the prepared pure/phosphorus-doped titania nanotubes was performed using transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), XRD analysis, UV–Vis absorption spectra, and BET specific surface area analysis. Phosphorus-doping slightly reduces the surface area but shifts the band gap towards the visible light region. When compared to pure TNTs, the optimal 0.75 wt.% P-TNTs have a similar surface area (272 m2/g vs. 274 m2/g) but with a band gap shift of 0.27 eV towards the visible light region. The photocatalytic activity of 0.75 wt.% P-TNTs was tested using rhodamine B (RhB) as a model pollutant under a 9 W fluorescent lamp and was significantly better than the benchmark Degussa P25 nanoparticles due to the band gap narrowing and an increased surface area. The decolorization follows first-order kinetics with the apparent rate constant k1 of 0.13 min−1 for 0.75 wt.% P-TNT and 0.07 min−1 for Degussa P25.

► Titania nanotubes (TNTs) and phosphorus-doped TNTs have a high specific surface area.
► As a result of phosphorus doping the band gap decreases from 3.22 eV (TNTs) to 2.95 eV.
► Phosphorus doping induce a discernable shift in the absorption edge towards the visible-light region.
► P-TNTs (0.75 wt.% P) have the highest photocatalytic activity.