Significantly enhanced visible light photocatalytic efficiency of phosphorus doped TiO2 with surface oxygen vacancies for ciprofloxacin degradation: Synergistic effect and intermediates analysis

In the present work, we reported a simple method for the simultaneous phosphorus (P) doping and oxygen vacancies creation on TiO2 in a single step. The obtained P-doped TiO2 with surface oxygen vacancies (PTSOV) samples exhibited efficient photocatalytic activity for the degradation of fluoroquinolone antibacterial agent (ciprofloxacin) under visible light irradiation. The optimized sample showed a rate constant of 0.065 min(-1) for degradation of ciprofloxacin (CIP) and it was about 16.2 times as high as that of TiO2 (0.004 min(-1)). The transformation products of CIP were identified by liquid chromatography-mass spectrometry (LC-MS), and degradation pathway was tentatively proposed. The doping state of P and the formation of surface oxygen vacancies (SOVs) were investigated by different methods. X-ray diffraction (XRD) and X-ray Photoemission Spectroscopy (XPS) revealed P5+ doped via formation Ti-O-P bond. Electron paramagnetic resonance (EPR) spectroscopy revealed that SOVs were generated on P-doped TiO2. It turned out that the synergistic effect between doping P and SOVs on TiO2 greatly improved transfer and separation efficiency of photogenerated charges, thus significantly enhanced the visible light photocatalytic performance of TiO2. Our work would provide an effective way to design new photocatalysts with high performance under visible light irradiation.