Electrochemical growth of SnS thin film: application to the photocatalytic degradation of rhodamine B under visible light

A facile and template-free wet electrochemical technique was used to deposit SnS on tin substrate. Longer time (>40 min) is required for the formation of the chalcogenide thin films and the potential must be carefully controlled to come out with a rough chemical identification of sulfide deposited at low potential scan. The deposition potential is selected from the cyclic voltammetry to preclude the oxidation of SnS to SnS2. The SnS films are uniform and well adhered to the substrate. They were characterized by X-ray diffraction, UV–Vis spectroscopy and electrochemical impedance spectroscopy (EIS). SnS crystallizes in an orthorhombic symmetry (SG: Pnma) and a crystallite size of 42 nm was obtained. The Mott–Schottky plot exhibited a linear behavior with a negative slope, characteristic of p-type conductivity. Holes density of 9.75 × 1020 cm−3, a flat band potential of 0.56 VSCE and a depletion width of ~38 nm were determined. The valence band was located at (−5.41 eV/0.66 V) and derives mainly from S2−: 3p while the conduction band (3.8 eV/−0.95 V) was primarily made up of Sn2+: 5p orbital. The EIS spectra measured over the frequency range (3 × 10−3–105 Hz) revealed mainly a bulk contribution. On application, rhodamine B was successfully oxidized on SnS films, 38% of the initial concentration (10 mg L−1) disappeared after 4 h of exposure to solar light (90 mW cm−2).