Synergistic effects of Ce and Mo co-doping for enhancing photocatalytic activity of BiVO4 on methyl orange degradation

We successfully synthesized Ce and Mo co-doped BiVO4 via the hydrothermal method and investigated the effects of Ce and Mo ions co-doping on the physicochemical and photocatalytic characteristics of BiVO4. Results of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-Vis diffuse reflectance spectra (UV-Vis DRS) indicate that the incorporation of Ce and Mo ions in BiVO4 can induce a tetragonal zircon phase, rod-like morphology, and widened band gap of the BiVO4 host. The measurement of methyl orange (MO) degradation under visible light irradiation indicates that the synergistic effects of Ce and Mo in the optimal doping of 0.0312 % Ce and 0.0312 % Mo co-doped BiVO4, called (0.0312Ce, 0.0312Mo)-BiVO4, shows a similar to 15-fold increase compared to the undoped BiVO4. From photoluminescence (PL) and time-resolved photoluminescence (TRPL) measurements, (0.0312Ce, 0.0312Mo)-BiVO4 shows the greatest reduction in the PL intensity and the shortest charge carrier lifetime of 4.55 ns relative to the undoped BiVO4, 0.0312Ce- and 0.0312Mo-doped BiVO4. These results suggest that charge carrier recombination in co-doped BiVO4 is suppressed and there is the rapid charge transfer from BiVO4 to dopant sites, respectively, leading to improved separation of electron-hole pairs. By testing photocatalytic activity, it was found that the dominant active species in the photodegradation process was h(+). In addition, the (0.0312Ce, 0.0312Mo)-BiVO4 shows high stability after four photodegradation cycling runs. Finally, the photocatalytic mechanism of the optimal (0.0312Ce, 0.0312Mo)-BiVO4 was proposed based on the cooperation of Ce and Mo dopants in the BiVO4 host for assisting charge transfer and enhancing charge separation in the photocatalytic process.