Preparation Of Doped Carbon Supported Ni,Cu And Ag Nanomaterials And Their Catalytic Performances Toward Reduction Reactions Of 4-Nitrophenol And Rhodamine B

The reduction reaction of nitrophenol compounds is the main reaction for the preparation of various dyes and organic intermediates.This reaction can also reduce the toxicity of nitrophenol compounds.However,although the reaction is thermodynamically spontaneous,its kinetic reaction rate is relatively slow,and a catalyst must be used.Supported metal-based nanocatalysts have attracted the attention of researchers due to their excellent catalytic performance.Common methods for preparing supported metal-based nanocatalysts include solution reduction method and metal organic framework thermal decomposition method.In this paper,we report the sol-gel method for preparation of carbon-supported metal nanomaterials and explore the catalytic performances of their catalytic performances toward hydrogenation reduction degradation of 4-nitrophenol and rhodamine B.The specific research contents and results are as follows:(1)The influence of different kinds of organic sources on catalytic performance was explored.Using the sol-gel method,nitrogen-free carriers(for example,ethylene glycol and urea,citric acid and urea)and nitrogen-containing carrier amine compounds(for example:propionamide,acrylamide,octadecylamine)were used to prepare nickel metal nanoparticles/Nitrogen-doped carbon(Ni/NC)nanomaterials where metal nanoparticles are supported by NC.The nanomaterials were characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS)and other methods to invstigate the crystalline phase,grain size,surface chemical elements of the nanomaterials.Then the nanomaterials were used as catalyst toward hydrogenation reduction degradation reaction of 4-nitrophenol and rhodamine B by employing Na BH₄ as reducing agent.The Ni/NC nanomaterials have excellent catalytic effect toward 4-nitrophenol and rhodamine B.The reaction is a pseudo first-order reaction.When the molar ratio of sodium borohydride to 4-nitrophenol is 1590:1,the sample's catalytic activity K value can be as high as 609.28 s^-1·g^-1,which is higher than the activity value reported in the literatures.When the molar ratio of sodium borohydride to rhodamine B is 500:1,the catalytic activity K value for degrading rhodamine B is 508.63 s^-1·g^-1.Comparative studies have shown that the excellent catalytic performance can only be obtained when metal element,carbon element and nitrogen element are co-existed,and the catalytic activity is reduced after acid treatment.Therefore,it is preliminarily considered that the main active center originates from the interface effect between metal nanoparticles and nitrogen doped carbon.(2)The influence of different doping elements on catalytic performance was explored.The sol-gel method was used to prepare carbon-supported Ni-based catalysts with iodine,phosphoric acid,and thiourea as raw materials for I doping,P doping,and S doping,respectively.Results have shown that the materials prepared by I doping are crystalline,while the materials doped with P and S are amorphous.Unexpectedly,the materials prepared by doping with these three elements also have good catalytic effects on the hydrogenation reduction reaction of 4-nitrophenol.The reaction is also a pseudo first-order reaction when doped with I element,and the highest catalytic activity K value is 467.85 s^-1·g^-1 can be obtained when the molar ratio between sodium borohydride and 4-nitrophenol is 1590:1.When P and S are doped,the reduction reacton it is a zero-order reaction.(3)The effects of other metals on the catalytic performances were explored.By using acrylamide as the carrier of C and N elements,Cu/NC and Ag/NC nanomaterials were prepared by this sol-gel method.The materials were also characterized by XRD,TEM and XPS,and the catalytic behavior was also explored.For the catalytic degradation of4-nitrophenol,the highest K value of Cu/NC catalytic activity is 330.92 s^-1·g^-1,and the highest K value of Ag/NC catalytic activity is 1402.1 s^-1·g^-1 The catalytic performance of Cu/NC is similar to that of Ni/NC,and Ag/NC has better catalytic performance than Ni/NC.