Visible light driven photoelectrochemical sensor for chromium(VI) by using BiOI microspheres decorated with metallic bismuth

Composites were prepared from BiOI and Bi/BiOI-X (where x can be 1, 2, 3, or 4) by a one-step solvothermal method and used to design a photoelectrochemical (PEC) assay for chromium(VI). The chemical composition and morphology of the materials were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The results of UV-vis DRS (Diffuse reflection spectra) and photoluminescence show the composites to have higher visible light absorption and a lower electron recombination rate compared to BiOI alone. Photogenerated electrons reduce hexavalent chromium to trivalent chromium, andthe consumption of electrons cause noticeable enhances of the photocurrent density after the addition of Cr(VI). Thus, the Cr(VI) concentration can be measured by monitoring the increase of photocurrent density. The Bi/BiOI-3 material displays the best performance for detecting Cr(VI). The method has a wide linear range (1 to 230M) and a low detection limit of 0.3M (at S/N=3). It is stable, selective, reproducible and was applied to the determination of nitrite in spiked tap water and lake water samples.