Abstract
CdS/NiS nanocomposites were synthesized by electrochemical method. Ni and Cd is one of the important II-VI semiconducting materials with a direct band gap of 3.26 eV which finds applications in electrical conductivity and photo-catalysis. The synthesized nanocomposites were characterized by BET, UV-VIS, XRD, FE-SEM (EDAX) techniques. X-Ray diffraction (XRD) reveals crystallite size to be 23.22 nm which was calculated using Williamson-Hall (W-H) plot method. The energy of the band gap for CdS/NiS could be thus estimated to be 3.26 eV. The photocatalytic activity of the sample was evaluated by the degradation of textile dye methylene Blue (MB) in aqueous solutions under UV radiation. Hydrogen energy is regarded as a promising alternative in terms of energy conversion and storage. Hydrogen Evolution Reaction (HER) was carried out in both visible light and UV light by using Hydrazine (N2H4H2O) in the presence of CdS/NiS nanocomposite. The synthesized photocatalyst shows applicable performance for kinetics of Hydrogen Evolution Reaction (HER) in Visible light and UV light. The decomposition of hydrazine (N2H4H2O) proceeded rapidly to generate free hydrogen rich gas through OH radical contact with CdS/NiS nanocomposite at room temperature. The rate of HER is limited by either proton adsorption onto an active site or evolution of formed hydrogen from the surface. A high Tafel slope is indicative of proton adsorption as the rate limiting step, while a lower Tafel slope (20 - 45 mV) indicates that the evolution of molecules hydrogen from the catalyst is rate limiting. In the present case the Tafel slopes for visible light 23.5 mV and 42.5 mV for UV light. Blank experiments show poor activity for HER i.e. 10.1 - 13.5 mV.
Highlights
cadmium sulphide (CdS) is one of the most studied materials among the II-VI compounds
X-Ray diffraction (XRD) pattern was recorded with pan analytical X-ray diffractometer using Cu Kα radiation (λ = 1.5406 Å), The morphological properties of the Ni/CdS nanoparticles were examined by scanning electron microscopy (SEM), The elemental analysis of the Ni/CdS nanoparticles was carried out using EDAX (JOEL, JED-2300, Germany), 3.1
BET surface area analysis and nitrogen adsorption-desorption isotherms were used to evaluate the properties like surface area, pore volume, pore diameter of CdS/NiS nanocomposite
Summary
CdS is one of the most studied materials among the II-VI compounds. II-VI semiconducting chalcogenide nanoparticles, especially sulfides and selenides have been investigated extensively, owing to their interesting optoelectronic properties [1] [2]. Visible light assisted hydrogen generation from complete decomposition of hydrous hydrazine using rhodium modified TiO2 photocatalyst as been reported by Pawan Kumar et al [14] [15] Semiconductor based photocatalysts such as TiO2, ZnO, InVO4, (Ga1 − xZnx) (N1 − xOx), etc. In continuation of our ongoing research on photocatalytic reactions, we report for the first time, visible light (laboratory condition) and UV light assisted hydrogen generation from hydrazine hydrate using CdS/NiS photocatalyst. In this method CdS/NiS nanocomposite was synthesized by electrochemical method. The increase in percent transmission and decrease in COD (mg/L) of dye solution with colour removal was observed to be more in CdS/NiS nanocomposite
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