Domestic microwave-assisted synthesis of Pd doped-BiVO4 photocatalysts

Palladium-doped bismuth vanadate (Pd-doped BiVO4) with different amounts of palladium have been successfully synthesized via domestic microwave-assisted method in an aqueous medium. XPS spectra verified that valence states of XPS spectra verified that the presence of Pd2+ species in Pd-doped BiVO4, while the valence state of Bi was observed as Bi3+. The XRD results implied that Pd doping can change the phase structure of BiVO4 from tetragonal to monoclinic, thus a mixture of monoclinic and tetragonal phase was detected in Pd-doped BiVO4. Field emission scanning electron microscopy (FESEM) revealed the mixed particle morphologies between them with EDX line scans of elements Bi, V, O and Pd. The photoluminescence spectroscopy (PL) results demonstrated that the forming Pd-BiVO4 depressed the recombination of photogenerated charges as well as the decreased of band gap determination from DRS, and photocatalytic performance was improved by the substitution of Pd2+ for Bi in BiVO4. The photocatalytic activities of the prepared samples were evaluated by degrading malachite green (MG) under visible-light irradiation for 150 min. The 2.0 wt%Pd doping exhibited the highest photocatalytic activity (98 %) while photocatalysis of 20 % was achieved by MG solution without catalyst. The photodegradation rate of the 2.0 wt% Pd-doped BiVO4 for MG removal was 5 times greater than that of a single BiVO4 and it can also be reused three times. The proposed mechanism of the enhanced photocatalytic activity was discussed. A possible mechanism of Pd-doped BiVO4 on the enhanced photocatalytic activity was also proposed.