One dimensional CdS/ZnO nanocomposites: an efficient photocatalyst for hydrogen generation

Abstract

One-dimensional ZnO nanostructures were synthesized using solvothermal reaction method, and in situ CdS nanoparticles were grown on 1D ZnO having different CdS compositions such as 0.1, 0.5, 1 and 5 mol% using microwave reaction system. The prepared CdS/ZnO coupled semiconductor catalysts were characterized using various spectroscopic techniques. XRD analysis indicated the presence of a wurtzite structure for all the prepared CdS/ZnO compositions. DRS spectrum showed red shift in the absorbance edge of CdS/ZnO nanocomposites with increasing CdS mol% and absorbance increases in 400 to 500 nm range. Photoluminescence spectra illustrated two emission peaks, with the first one at 390 nm due to the band edge emission of ZnO and the second broad peak centered around 480 nm possibly due to CdS band edge emission or oxygen vacancies in ZnO. FESEM image showed the formation of pencil shaped one-dimensional ZnO nanorods containing spherical CdS nanoparticles on the surface of ZnO. TEM analysis confirms the rod-like morphology of ZnO and the presence of CdS nanoparticles. The activity of the prepared CdS/ZnO catalysts was evaluated by measuring the amount of H₂ generated during photocatalytic H₂ evolution from water. The photocatalytic activity of prepared coupled CdS/ZnO shows an increase in hydrogen generation compared to that of individual ones. CdS loading enhances the rate of H₂ generation and is the highest for 5 mol% CdS/ZnO composition.