One-step preparation of Ag-incorporated BiVO4 thin films: plasmon-heterostructure effect in photocatalytic activity enhancement

Ag-incorporated BiVO4 thin film with high photocatalytic activity is a great candidate for industrial wastewater treatment, enhancing the photoactivity of BiVO4, as well as solving the recyclability and reusability drawback of powder photocatalysts. Therefore, a novel one-step process of the reactive magnetron sputtering technique was employed, which to this day was never utilized to synthesis Ag-incorporated BiVO4 thin films. The effect of Ag incorporation on the photocatalytic properties was comparatively investigated. The photoactive phases e.g. monoclinic BiVO4, Ag4V2O7, alpha-AgVO3 were detected by X-ray diffraction (XRD). Various morphologies, depending on the Ag content, were observed by field emission electron microscopy (FESEM) along with Ag nanoparticles on the film surface. X-ray photoelectron spectroscopy (XPS) proved the existence of Bi and V exclusively in their Bi+3 and V+5 oxidation states, while Ag was present in Ag+ and Ag-0, which are correspondent with silver vanadates and Ag nanoparticles, respectively. The thin film with 24 at. % Ag exhibited superior photocatalytic performance with a 99 % photodegradation of Rhodamine-B at neutral pH under visible light, as a result of having the lowest bandgap (1.96 eV), proper distribution of Ag4V2O7 phase, the plasmonic effect of Ag nanoparticles on the film surface, and the lower recombination rate compared to the pristine sample demonstrated by photoluminescence (PL) spectra. The recyclability experiment ensured the high stability of the thin films after three consecutive cycles, and the role of superoxides (O-center dot(2)-) and photogenerated holes were found to be crucial using scavengers. The results confirmed the synergistic enhancement of the photocatalytic activity through Ag-incorporated BiVO4 heterostructure and the plasmonic effect, as well as solving the low photoactivity of BiVO4 at neutral pH.