N-Doped Nb2O5 Sensitized by Carbon Nitride Polymer - Synthesis and High Photocatalytic Activity under Visible Light

N-doped Nb2O5 sensitized by carbon nitride polymer (CNNO) was synthesized as a yellowish powder by using urea as a carbonnitrogen precursor. CNNO was tested as a catalyst for the visible-light-responsive photodegradation of dyes. HNbO3, one of the precursors of CNNO, was obtained from LiNbO3 by a H+Li+ ion-exchange reaction and then pyrolyzed at 400 degrees C to produce a Nb2O5 substrate. The photocatalytic activities of as-prepared samples were evaluated by the degradation of Rhodamine B (RhB) under Xe lamp irradiation (??> 400 nm), for which the photocatalysts showed relatively high activities. XRD, thermogravimetry and differential scanning calorimetry (TGDSC), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), TEM, X-ray photoelectron spectroscopy (XPS), UV/Vis diffuse reflectance spectroscopy (DRS), and BrunauerEmmettTeller (BET) measurements were utilized to explore the characteristics of the obtained samples. The results demonstrated that the surface of Nb2O5 was successfully coated, as a semitransparent layer of CN polymer surrouding the dark substrate was observed. UV/Vis DRS showed that the absorption edges of CNNO were shifted remarkably to the visible region relative to those of naked Nb2O5. These results revealed that the significantly enhanced photocatalytic activities of the CNNO samples originate from the CN polymer. The coating led to an efficient electron transfer between the CN polymer, which acted as a photosensitizer, and the N-doped Nb2O5. The degradation mechanism that underlies the excellent photocatalytic activity of CNNO was discussed extensively.