Photoactivity of nanostructured spheres of BiVO4 synthesized by ultrasonic spray pyrolysis at low temperature

Brain-like nanostructures of BiVO4 were synthesized by ultrasonic spray pyrolysis (USP) using citric acid as chelating agent at 350 degrees degrees C. Synthesis variables such as carrier gas flow, structural agent concentration and temperature were herein studied. The samples were characterized by XRD, SEM, TEM, UV-Vis DRS and N-2 physisorption. Particularly, HRTEM was used to calculate the crystallite size, d-spacing and assigned plane of all BiVO4 samples. The photoactivity of the as-synthesized BiVO4 was measured during the degradation of methyl orange under visible-light irradiation, while the hydroxyl radical production was rated in terms of its reactivity against terephthalic acid. The morphology of the samples revealed that the use of small flow of N-2 allows the formation of spherical hollow porous particles with brain-like structure with slightly smaller crystallite size. The photocatalytic activity of the BiVO4 photocatalysts prepared by USP displayed a performance three times greater compared to the powders produced by co-precipitation. The PL spectra measured revealed that the charge separation process of the BiVO4 powders synthesized by the USP technique was better compared to those obtained by co-precipitation. The energy diagram of the photocatalyst reveals that the usage of the USP technique does not require the formation of a heterojunction to efficiently promote the separation of photogenerated carriers, since it removes defects in the gap which generating states which that induce the recombination; and shorten down the transferring distance from the excitation zone to the active site on the surface of the BiVO4 due to the production of nanostructures.