Hydrothermal synthesis of TiO2 nanosheets photoelectrocatalyst on Ti mesh for degradation of norfloxacin: Influence of pickling agents

TiO2 nanosheets (TiO2-NSs) photoanodes were synthesized on the surface of Ti meshes via the hydrothermal method, and then washed by HCl, HNO3 and H3PO4, respectively. The TiO2-NSs washed by different pickling agents were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electrons microscopy (SEM), and UV–vis diffuse reflectance spectra (DRS). The results showed that P and N were transferred into the lattice of TiO2. The TiO2-NSs samples washed by HCl and HNO3 both had a mixture of anatase and rutile structures, while the TiO2-NSs washed by H3PO4 only contained anatase phase. It could be concluded that H3PO4 pickling inhibited the formation of rutile phase. Moreover, TiO2-NSs washed by HNO3 (TiO2-NSs-HNO3) exhibited the strongest light absorption ability in visible region. Photoelectrochemical properties of the TiO2-NSs photoelectrodes washed by different agents were investigated via transient photocurrent response (TPR), open-circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). The photocatalytic (PC) and photoelectrocatalytic (PEC) performances were evaluated by the degradation of norfloxacin and the yield of
• OH radicals in the reactors. The results showed that the TiO2-NSs-HNO3 photoelectrode revealed the highest photoinduced current of 1.08 mA/cm2, open-circuit photovoltage of −0.22 V, PEC efficiency of 93% for the removal of norfloxacin. In addition, the enhanced PEC mechanism for TiO2-NSs-HNO3 was proposed. The high PEC activity of TiO2-NSs-HNO3 could be attributed to the introduction of N during acid-washing procedure, which could not only reduce the band gap energy but also accelerate the separation and transportation of photogenerated charge carriers.