La and F co-doped Bi2MoO6 architectures with enhanced photocatalytic performance via synergistic effect

Abstract

Novel La and F co-doped Bi₂MoO₆ architectures were first successfully synthesized via a facile solvothermal process, and characterized using XRD, SEM, TEM/HR-TEM, XPS, EDS, UV-Vis DRS and PL spectra. The enhanced photocatalytic activities of La and F co-doped Bi₂MoO₆ architectures were evaluated by the photodegradation of rhodamine B (RhB) under visible-light irradiation. The results demonstrated that the F-1.0 at% La–Bi₂MoO₆ photocatalyst exhibits significantly enhanced photocatalytic activity, which is 6.54 times higher than that of pure Bi₂MoO₆. The cause can be attributed to the co-incorporation of La and F into Bi₂MoO₆ broadening the absorption in the visible-light region and thereby leading to the formation of new energy levels on top of the valence band of F–La–Bi₂MoO₆, and on the other hand, the synergistic effect of F and La, in which F doping led to the increase of absorptivity of F–Bi₂MoO₆ and acted as an n-type impurity to supply a hole carrier. The doped La³⁺ ions act in a key role to capture and transfer/release the photogenerated electrons for conversion from O₂ to ·O₂⁻ to delay the recombination of the photogenerated electrons and holes, greatly suppressing the recombination of photogenerated electron–hole pairs and thus significantly improving photocatalytic activity in RhB photodegradation. The radical capture experiment confirmed that h⁺ and ·O₂⁻ were the main active species and were responsible for RhB photodegradation. Moreover, on the basis of the PL spectra, active species trapping detection and photocurrent response experiments, the mechanism of the enhanced photocatalytic activity for F–La–Bi₂MoO₆ was proposed.