Enhanced photocatalytic efficiency of TiO2/CdS nanocomposites by manipulating CdS suspension on TiO2 nanoparticles

Abstract

• TiO 2 /CdS nanocomposites are synthesized at different concentrations of cadmium and sulphur precursors. • The Cd and S precursors ratios affect the size and morphologies of resulting nanocomposites. • Photocatalytic activities are influenced by the precursor ratio. • Stepwise de-ethylation for RhB is observed during visible light photocatalysis. Titanium Dioxide (TiO 2 ) has long been found to be a promising photocatalyst in the ultraviolet region, although it faces several limitations in the visible range. Various attempts for overcoming these shortcomings have shown that TiO 2 nanocomposites offer excellent results for visible area photocatalysis. In the present work, three different samples of TiO 2 /CdS nanocomposites are synthesized using simple and cost-effective hydrothermal method, based on different concentrations of cadmium and sulphur precursors and a comparison is made among them. Characterization techniques like Scanning Electron Microscopy (SEM), Photoluminescence (PL) spectroscopy, UV-visible spectroscopy, X-Ray Diffraction (XRD), Energy Dispersive X-Ray Analysis (EDX) and Fourier Transform Infrared (FTIR) spectroscopy are employed to study morphological, optical, structural, and elemental properties of the as-synthesized nanocomposites. SEM analysis shows that change in concentration of precursors caused morphological changes in the resulting samples. XRD characterization shows that the crystallite size gets modified at different concentrations ranging from approximately 21 nm to 5 nm. As per the UV-Vis spectroscopy, the band gap of TiO 2 /CdS nanocomposites has substantially decreased, making it highly suitable for photocatalytic application in the visible region in comparison to pure TiO 2 . Photocatalytic degradation processes for as-synthesized TiO 2 /CdS nanocomposites are studied for methylene blue (MB) and rhodamine B (RhB) dyes under visible light exposure. Results demonstrate that degradation results for MB dye are better in comparison to RhB dye for all the three synthesized photocatalysts. Futher, it is concluded that TiO 2 /CdS nanocomposite with a 1:1 molar ratio of cadmium and sulphur precursors has the optimum photocatalytic performance for dye degradation.