Photo-Fenton degradation of ciprofloxacin over Cu, Ce co-doped monoclinic BiVO₄ photocatalyst

We resort to aliovalent co-doping of BiVO₄ to prepare Cu, Ce-doped BiVO₄ photo-Fenton catalysts for ciprofloxacin degradation. Different compositions of co-doped BiVO₄ were prepared by a hydrothermal synthesis protocol, and the sample with one mole percent Ce and two mole percent Cu (CE1CU2) exhibited optimum ciprofloxacin degradation photo-Fenton catalytic activity. Detailed structural characterization showed the formation of the monoclinic scheelite phase, along with the existence of Cu⁺/Cu²⁺ and Ce³⁺ in the co-doped BiVO₄. The CE1CU2 sample demonstrated a lower charge recombination rate, thereby prolonging the electron lifetime and facilitating the reduction of H₂O₂ to ˙OH radicals. Moreover, the co-doped BiVO₄ maintains high photocatalytic activity for ciprofloxacin degradation until the fifth reuse cycle. The active radical-trapping experiments confirm that ˙OH is the dominant reactive species, with contributions from e^-, h⁺, and O₂˙^- active species. It appears that synergistic Ce³⁺/Ce⁴⁺ and Cu⁺/Cu²⁺ redox cycling facilitates continuous radical generation, regenerating the CE1CU2 catalyst and thereby enhancing its photo-Fenton performance and stability.