Synthesis of nanocomposite CdS/TiO2 and investigation of its photocatalytic activity for CO2 reduction to CO and CH4 under visible light irradiation

CdS-TiO2 nanocomposites were synthesized with various CdS weight ratios of 9%, 23%, 45% and 74% by the hydrothermal process. The prepared samples were characterized by X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy (DRS), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS) and Brunauer-Emmett-Teller (BET) analysis. Samples were coated on the surface of the perforated stainless steel and the photocatalytic activity of the catalysts was investigated under both UV-visible and visible irradiation to convert CO2 to carbon monoxide and methane. Significant improvement was observed for the activity of CdS-TiO2 nanocomposites compared with pure nano TiO2 under both UV-visible and visible light scattering in a batch gaseous reactor. The activity of CdS-TiO2 nanomaterial was found to be related to the CdS content and the size of nanoparticles. Maximum photocatalytic activity was observed for an optimal weight ratio of 45% CdS/TiO2 with 13 nm average crystal size. The photocatalytic experiments were taken for 8 h and formation of CO and CH4 was detected in gas phase, whereas CO production was five folds more than methane formation. Under UV-visible irradiation, photocatalytic activity of CdS-TiO2 for CO and CH4 formation was observed 35% and 50%, respectively, more than that under visible light. (C) 2014 Elsevier Ltd. All rights reserved.