Synthesis of CdS/MgAl layered double hydroxides for hydrogen production from methanol-water decomposition

MgAl layered double hydroxide with molar ratio Mg/AI = 3:1, and CdS/MgAl containing 5, 10,15 and 20 wt% of CdS were synthesized by the co-precipitation method. X-Ray diffraction (XRD) of the solids showed characteristics reflections of hydrotalcite type materials in a hexagonal lattice with R-3m rhombohedra symmetry, additionally a wurtzite type hexagonal crystalline structure of CdS which is the most efficient crystalline phase as photocatalysts. Nitrogen adsorption isotherms were obtained and specific surface areas around 30 m(2)/g for all the CdS/MgAl solids were found which are of the same order found on the MgAl LDH. Fourier transform infrared spectroscopy (FTIR) spectra showed an intense band characteristic of v(3) vibrations (antisymmetric stretching) of CO32- ions located in the interlamellar region of the LDH and it remains constant in the CdS/MgAl samples. Scanning Electron Microscopy study coupled to a detector for energy dispersive X-ray spectroscopy microanalysis (SEM/EDS) showed that the CdS is well dispersed on the surface of the MgAl. UV-Vis spectroscopy showed that the ban-gap Eg of the samples is around 2.30 eV close to that obtained in the CdS reference solid (2.26 eV). The photocatalytic activity under irradiation UV light of the compounds in the hydrogen production from the methanol-water decomposition was evaluated showing that the activity of CdS/MgAl photocatalysts after 7 h under irradiation was up to 20 times superior (1100 H-2 mu mol/CdSg) than the CdS (53 H-2 mu mol/CdSg), being the CdS/MgAl 5% the best photocatalyst. (C) 2016 Elsevier B.V. All rights reserved.