Preparation Of Nitrogen Doped Carbon Based Ni And Ni-Cu Nanomaterials By Sol-gel Method And Catalytic Reduction Of Nitrophenols

In recent years,carbon-based nanocomposites have been widely used in the field of catalysis,due to its unique physical and chemical properties and the ability of accelerating electron transmission,which attracts researchers'interests.In this thesis,the carbon-based metal nanomaterials have been synthesized based on thermodynamic standard principles and the catalytic performances were studied.The specific works are listed as follows:(1)The sol-gel method was used to prepare carbon-based nickel/N-doped carbon(Ni@N/C)nanomaterials using ethylene glycol as chelating agent.The crystal phase,particle size,and magnetic properties of samples calcined at different temperatures were analyzed through a series of characterization,X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and vibrating sample magnetometer(VSM).The test results show that the Ni₃C phase can be identified in the sol–gel method by changing the initial molar ratio of Ni²⁺:ethylene glycol(EG)from 8:1 to 1:10.When urea is used as nitrogen source for nitrogen doping,Ni²⁺:EG=1:10,the as-prepared catalysts have excellent catalytic performance toward hydrogenation reduction reaction of 4-nitrophenol.The activity parameter is calculated to be 74.56s^-1g^-1.Then nitrogen-doped Ni@N/C was prepared by sol-gel method using citric acid and green plant extracts as chelating agents.The materials also have good catalytic reduction performance on4-nitrophenol,2-nitrophenol and nitrobenzene,the K value of catalytic reduction of4-nitrophenol by Ni@N/C prepared with oleander extract as chelating agent can reach 121.9s^-1g^-1.(2)The effects of different catalyst dosage and different chelating agents on the catalytic reduction reaction of 4-nitrophenol were studied.It was found that when the dosage of catalyst was reduced to 1/3 of the original dosage,the catalytic effect was not weakened.When urea is used as nitrogen source for nitrogen doping,Ni²⁺:EG=1:4,the K value of catalytic reduction of 4-nitrophenol can reach 659.8 s^-1g^-1 by Ni@N/C The catalytic effect of acids as chelating agents is weaker than that of the same type of polycols with the same quantity of C.(3)The effect of different metal carbon-based nanomaterials on the catalytic performance was studied.When agar was used as a chelating agent,as for catalytic reduction of4-nitrophenol,it was found that the performance of carbon-based copper-nickel nanomaterials prepared at a lower temperature with copper atoms introduced was better than that of pure carbon-based nickel nanomaterials.