Improved photocatalytic activity of Z-scheme β-Bi₂O₃/Bi₂WO₆ nanocomposites from band bending of p-n heterojunction

Photocatalytic β-Bi₂O₃/Bi₂WO₆ p-n heterojunctions were synthesized by two-step solvothermal method, and then, the phase structure, microstructures, and band structures were characterized with XRD, EDS, N₂ adsorption-desorption isotherms, and UV-vis spectroscopy. The β-Bi₂O₃ nanoparticles with the smaller diameter anchor on the surface of Bi₂WO₆ nanoparticles to form β-Bi₂O₃/Bi₂WO₆ nanocomposites, resulting in the band bending for the balance of Fermi level. The band bending of p-n heterojunctions leads to the Z-scheme β-Bi₂O₃/Bi₂WO₆ photocatalysts and electron narrow energy transition between Ec of Bi₂WO₆ and Ev of β-Bi₂O₃. The accumulation of electrons at E_C of β-Bi₂O₃ and holes at E_V of Bi₂WO₆ both improve the photocatalytic activity of β-Bi₂O₃/Bi₂WO₆ nanocomposites. The photocatalytic removal of ciprofloxacin increases up to about 93% for S-20 with the increasing β-Bi₂O₃ content under visible light irradiation. Therefore, the β-Bi₂O₃/Bi₂WO₆ photocatalysts with the dominant radical of •O₂⁻ and holes could be regarded as one of promising candidates in the fields of dealing with antibiotics.