Peparation, Characterization And Properties Of Multi-function Supported Nano Nickel Catalyst

As an important chemical intermediate,4-Aminophenol（4-AP）has been widely used to synthesize analgesic and antipyretic drugs,anticorrosion lubricants,dyestuffs and so on.while 4-nitrophenol（4-NP）is a common organic pollution in the industrial and agricultural waste water.An efficient and environmentally friendly conversion route is the direct reduction of 4-NP to 4-AP.Many researchers pay attention to make this eco-friendly route come true.As a result,various methods such as the hydrogenation of nitrobenzene in the presence of strong acid as well as transition metal-catalyzed hydrogenation of 4-nitrophenol etc.have been employed in order to obtain 4-AP efficiently.However,considering the fewer by-products and the less environmental problems,the direct conversion of 4-nitrophenol（4-NP）into 4-AP catalyzed by transition metal catalyst has attracted intensive attention in the past two decades.Especially with the rapid development of nanotechnology,many transition metal nanocrystals,like Au,Ag,Pd,Pt,Cu,Co,and Ni etc.demonstrated unusual catalytic activity for the conversion of 4-NP into 4-AP and were employed intensively.So how to improve the catalytic activities of the supported transition metal catalysts become the research focus.The synthesis of Ni/rGO support with highly dispersed Ni nanoparticles and uniform particle size on the surface of reduced graphene oxide（rGO）was designed in this study,during which Ni nanoparticles and rGO were formed simultaneously by combining in situ thermal decomposition and reduction in 5%H₂/N₂ gas at 600℃.The introduction of Ni on the surface of rGO endow the as-prepared Ni/rGO with more functions,such as catalysis and magnetic separation besides the inherent properties of rGO.Afterwards,the Au nanoparticles were successfully anchored on Ni/rGO through in-situ reduction of HAuCl₄ using NaBH₄ as reducing agent.The as-prepared Ni/rGO@Au catalyst shows excellent activity towards the conversion of 4-nitrophenol into 4-aminophenol in the presence of NaBH₄ in comparison with the Ni-decorated rGO that also has catalytic activity for the reduction of 4-nitrophenol,the activity parameterκof the Ni/rGO@Au is almost three orders of magnitude higher than that of Ni-decorated rGO,and after magnetic separation the catalyst can be reused and show no obvious decrease in the conversion at the end of the 8th cycle.