Synthesis And Catalytic Oxidation Properties Of Molybdenum Disulfide Composites Pillared By Hydroxy-Al Oligocations

Molybdenum disulfide composite materials pillared by inorganic or organic molecules(or ions) are provided with the properties of anisotropy, electricity, magnetism, catalysis and so on, which are expected to make them apply in the several areas such as electrode materials, petrochemical industry and environment protection. Due to the insufficient researches in molybdenum disulfide composites pillared by inorganic guests, the pillared nanocomposites were prepared by intercalating the hydroxy-Al oligocations into the interlayers of the molybdenum disulfide host sheets through the single-molecular-layer exfoliated-restacked technology. The structures and properties of the pillared composites were investigated by means of XRD, DSC, SEM, IR, UV-Vis, DRS, BET, EDS etc. The results showed that the basal interlayer spacings of the pillared composites are from 1.481 to 1.521 run, where the intercalated Keggin species are arranged in a mono-layer fashion between the molybdenum disulfide sheets with their C₃ symmetry axes perpendicular to the host sheets. It was revealed that a lower concentration of pillaring agents and a lower ratio of Al/MoS₂ in reaction system will result in a larger interlayer spacing. Compared with the pristine 2H-M0S2, the pillared nanocomposites exhibit larger interlayer spacings, smaller crystallite sizes and larger specific surface areas. Hydroxy-Fe-Al and -Ni-Al oligocations with a Keggin structure, prepared by a substitution reaction, were intercalated into the molybdenum disulfide host interlayers, and the pillared composites possess the basal interlayer spacings from 1.394 to 1.513nm and 1.211 to 1.472 nm, respectively. It was shown that the interlayer spacings of the pillared composites decrease with the increasing of Fe/Al and Ni/Al molar ratio.The catalytic and photocatalytic activities of the as-prepared pillared composites were studied in the oxidization of sulfide ions. The experimental results indicated that the pillared composites exhibit good catalytic activities in the oxidization of sulfide ions into thiosulfate ions, being three to eight times higher than that of the pristine 2H-MoS₂. The catalytic activities are enhanced upon irradiation with visible light owing to the semiconducting 2H-MoS₂ matrix. The results are related to their smaller crystallite sizes, larger specific surface areas, the existence of the defects and the lattice distortion. It was illustrated that the catalytic activities are improved by introducing the iron and nickel into the pillared composites.