Synthesis, characterization and crystal structure of a novel Sr (II)- Cu(II) complex, a precursor to produce catalyst of Cu-Sr/SiO2, applicable for hydrogen production

A new hetero-dinuclear complex [(Sr(OH2)6Cu(H2O)4 Sr2 (dipic)4(OH2)2]n.nH2O (CS) that dipic2- is pyridine-2,6-dicarboxylato has been synthesized under ultrasonic irradiation. The structure of the CS complex has been fully characterized by elemental analysis, Fourier transforms infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential thermal analysis (DTA) and single-crystal X-ray diffraction (SC-XRD). The results of crystallography analysis revealed that this complex crystallizes in a triclinic system with space group P -1. It also confirms the large number of H-O ... O hydrogen bonds play a key role in the creation of the 3D network. The Sr-Cu/SiO2 nano-catalyst was prepared by thermal decomposition of CS complex at 600ºC in the presence of silica support. In addition, reference catalysts of Cu-Sr/SiO2 were prepared by co-precipitation and impregnation methods and characterized by FT-IR spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and specific surface area (BET). The results of these studies show that the catalyst obtained by the thermal decomposition of the CS complex has smaller particle size and larger specific surface area than the two reference catalysts. In order to produce hydrogen gas, a water-gas shift reaction (WGS) was performed on the surface of Cu-Sr/SiO2 nanocatalysts in the temperature range of 300-420ºC. Examination of the effect of temperature shows that at 380ºC the catalytic activity of all three catalysts is at its highest. The highest catalytic performance was achieved by nanocatalyst that derived from CS complex. This high catalytic performance can be attributed to the physicochemical properties of this catalyst such as smaller particle size and higher specific surface area.