Synthesis And Catalytic Properties Of Heterogeneous Catalysts

Fe₃O₄ are now widely used as magnetic core in heterogeneous catalysis,in which the catalysts can be easily recollected.CeO₂ is an ideal candidate due to its properties of low cost,high oxygen storage capability and high oxygen mobility.And porous carbon materials have also been widely used in many areas of modern science and technology owing to their high specific surface area,large pore volume,electrical conductivity,thermal stability and chemical inertness.Palladium nanoparticles?PdNPs?and copper species NPs have been paid special attention among the metals,owing to their multiple catalytic performances.Pd nanoparticles anchored on CeO₂-coated magnetic Fe₃O₄ were successfully synthesized.The core-shell nanocomposites?Fe₃O₄@CeO₂/Pd?were characterized,by Powder X-ray diffraction?XRD?,Magnetic properties?MH?,High resolution transmission electron microscope?HRTEM?and X-ray photoelectron spectroscopy?XPS?.The Fe₃O₄@CeO₂/Pd particles had an average diameter of about 9.55 nm and exhibited excellent catalytic activity for the reduction of 4-nitrophenol.Importantly,the nanocatalyst was easily recovered and could be reused for 4 times and still maintained high activity.The turn over frequency?TOF?of the best catalyst was 13.81 min^-1 and the TOF of 0.828 min^-1 in the fourth run was even higher than the one in the first cycle of many other catalysts,which was contributed to the synergistic effect among Fe₃O₄,CeO₂and Pd.The influence of preparing temperatures of CeO₂ shell on the catalytic activity exhibited that the higher the temperature was,the better the catalytic activity would be.And in this study,a hierarchical porous N-doped carbon?NHPC?was successfully synthesized as a catalyst support by a facile method.A large amount of Pd nanoparticles were uniformly loaded on the NHPC with average diameter of about 4.45 nm.The synthesized NHPC/Pd nanocatalyst exhibited excellent stability and reusability in the catalytic activity for the reduction of 4-nitropenol?4-NP?to 4-aminophenol?4-AP?at room temperature.The uniformity and high reusability of NHPC/Pd was mainly attributed to the abundant doped nitrogen as coordinated site to largely stable Pd nanoparticles.Herein,the excellent properties of NHPC provided ideas for the fabrication of NHPC supported other noble nanoparticles,which can be applied in various catalytic reductive reactions.Cu/Cu₂O/CuO were successfully composited on a kind of N-doped porous carbon?NC?materials through a facile hydrothermal method.The characteristics of the catalyst were investigated by HRTEM,SEM,XRD,XPS,surface area and porosity analysis?BET?and inductively coupled plasma mass spectrometry?ICP-MS?.The catalyst exhibited excellent catalytic activity in the reduction toward 4-NP with rate constant of 1208 s^-1·g^-1and reusability of 13 cycles in 5 mins.And the NC reached quick equilibrium within 19mins toward 4-NP in the adsorption experiment.The high activity was owed to the porous structure with large amount of nitrogen doped,which had large capacity of 4-NP and enhanced the interactions between active sites and NC.Moreover,the catalyst also exhibited intrinsic Peroxidase-like activity and could rapidly oxidize the substrate3,3',5,5'-tetramethyl-benzidine?TMB?in the presence of H₂O₂ with very low H₂O₂ detection limit of 5.86?M.Therefore,the catalysts prepared in this method derived from non-noble metals supported on N-doped porous carbon by facile synthesis strategy may expand new ideas in reductive reaction and application in analytical fields.