Photoelectrochemical determination of sulfide in water using a silver iodide/gold nanoparticle/fluoride-doped tin oxide electrode

Sulfides are widely used as industrial raw materials, but they also cause serious water pollution and pose a high risk to human health. Consequently, sensitive and selective methods for detecting sulfide ion (S2−) in water are required. In this work, a photoelectrochemical (PEC) sensor was proposed based on the precipitation-dissolution equilibrium between silver iodide (AgI) and S2− on a gold nanoparticle (AuNP)-modified fluorine-doped tin oxide (FTO) electrode. The sensor was characterized by scanning electron microscopy, X-ray diffraction, and UV–Vis spectroscopy and applied to detect S2− by measuring the photocurrent under Xe lamp irradiation. On the formation of Ag2S, the UV–Vis absorption spectrum of the electrode was red shifted and the absorbance increased significantly. Further, the photocurrent polarity was reversed as a result of the formation of Ag2S on the surface of AgI/AuNP FTO. Overall, the sensor showed high sensitivity and selectivity for S2− detection, and the detection was linear at 0.2–5.0 and 5.0–50.0 μmol/L with a limit of detection of 0.08 μmol/L. Crucially for practical applications, the sensor was reproducible and showed good recovery and accuracy in real samples. In summary, the proposed sensor owns advantages in simple fabrication, high sensitivity, selectivity, stability, and low cost, and has good application prospects in the environmental monitoring of S2−.