The Design Of Noble Metal Composites For Environmental Pollutants Management

In recent years,metal nanocomposites were playing an increasingly important role for the catalytic degradation of organic pollutants in the environmental management.Developping highly efficient metal nanocatalysts were attracting more and more research interest for applications in degrading environmental organic pollutants.With the deeper understanding about reaction mechanism,improvement of the exprimental technologies and improved ability in designing new structures of catalysts,the studies in catalysis have been expanded from macroscopic description to nanoscale and molecular lecel.This dissertation focused on the synthesis of nanomaterial based catalys with high activity,high selectility and high stability.The main content and results are as follows.(1)A Cu/CuO-Ag composite with structure that Ag and CuO nanoparticles(NPs)decorated on the surface of Cu were fabricated via a facile in-situ method.With the combination of characterization of transmission electron microscopy(TEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),energy dispersive X-ray spectroscopy(EDX)and inductively coupled plasma atomic emission spectrometry(ICP-AES),the structure and component of Cu/CuO-Ag composite were well-defined.The Cu/CuO-Ag composite exhibited superior catalytic activities for the reduction of 4-nitrophenol(4-NP)in the presence of NaBH4 with just trace amount of Ag NPs(1.28 wt%),as the reduction could be completed in 75 s with apparent rate constant kaPP of 4.60×10-2 s-1.Excellent durable stability was also achieved by Cu/CuO-Ag composite,and no activity loss was detected in the consecutive five cyclic utilization.With the aid of Sabatier principle and volcano plot,the opportune chemical adsorption energy of the reagent 4-NP on Cu/CuO-Ag composite was inferred to be the key to their high reaction rate.Moreover,the CuO NPs with the narrow band gap that could help the Cu/CuO-Ag composite to capture the electrons/hydride ions also provided larger surface area and increased opportunities for 4-NP to be reduced.What's more,the Cu/CuO-Ag composite exhibited outstanding activity on the oxidative degradation of methylene blue.The work enriched bimetals/semiconductor catalyst system and supplied new insight on the catalysis mechanism.(2)An Au-Fe2O3@mesoporous SiO2 nanoreactor with multi-yolks/shell structure was synthesized through a multistep method.In this nanoreactor,the spindle Fe2O3 and Au nanoparticles were inside the same mesoporous SiO2 shell as the yolks but in a noncontact manner.The noncontact synergistic effect between Au nanoparticles and the Fe2O3 spindle was studied with a Fenton-like reaction.The catalytic activity of the Au-Fe2O3@mesoporous SiO2 nanoreactor to the Fenton-like reaction for the degradation of organic dyes was dramatically enhanced by the noncontact synergistic effect.(3)We report an efficient and controllable route to prepare Pd@GLCs nanocomposites with the template of two-dimensional layered silicate RUB-15.The structure of Pd@GLCs nanocomposites were determined by TEM.XRD and EDX.The Pd@GLCs nanocomposites exhibits a high catalytic activity and excellent reusability for styrene hydrogenation under mild conditions.This study provides a facile route to fabricate Pd@GLCs nanocomposites with enhanced catalytic properties.