Study On The Controllable Synthesis And Properties Of Novel Iron-carbon Nanocomposite Catalysts

With the economic growth and social progress,people's demand for materials is also increasing.After the nanomaterials were proposed,there was an upsurge of research on nanocomposites.Transition metal elements and alloys have attracted extensive attention due to their unique physical and chemical properties,but their disadvantages,such as easy agglomeration and oxidation,seriously limit their application in various fields.Carbon nanomaterials are widely used as catalyst support materials to improve the stability of metal nanoparticles.In order to overcome the above problems,we combined the abundant transition metals on the earth with carbon materials to obtain multiple iron-carbon nanocomposites and applied them in catalytic reaction systems.This thesis with organic small molecules salicylic acid root(Sal-)for intercalated preparation for double metal hydroxide anion,and take it as a single precursor,adopt the method of solid phase synthesis of controllable preparation for a series of efficient and stable nanometer composite catalyst(Fe/ZnO/C and NiFe@C)and on photocatalytic degradation of organic dyes and alkaline conditions of electrochemical hydrogen evolution reaction to evaluate the catalytic performance.The specific research content is as follows:1?ZnFe-Sal LDHs of salicylic acid radical intercalation was formed by means of self-assembly in aqueous phase using cheap iron nitrate,zinc nitrate and sodium salicylate as raw materials.The Fe/ZnO/C ternary nanocomposite catalyst was prepared with ZnFe-Sal LDHs as a single precursor in an inert atmosphere through a controlled one-step solid-state pyrolysis reaction.SEM,XRD,HRTEM,FT-IR,Raman and XPS were used to analyze the composition,morphology and structure of Fe/ZnO/C ternary nanocomposite catalyst.The results showed that:the iron and zinc oxide nanoparticles in the prepared nanocomposite catalyst were uniformly dispersed in the graphitized carbon.The degradation rate of MB in visible light for 120min was more than 90%.The first-order kinetic simulation of catalytic reaction was carried out,and the chemical reaction kinetic constant k value was about 18 times that of commercial ZnO.At the same time,the high saturation magnetization is beneficial to the magnetic recovery of the catalyst.The catalytic activity of the Fe/ZnO/C nanocomposite catalyst was still high after 5 times of cyclic testing,indicating that the Fe/ZnO/C nanocomposite catalyst was a highly active and stable visible light catalyst.2?NiFe-Sal LDHs was successfully prepared by urea hydrothermal method with salicylate as intercalated anion and Ni and Fe transition metal elements were introduced into LDHs laminate.In the absence of reducing agent,template agent and additional carbon source,NiFe-Sal LDHs was used as a single precursor to obtain the NiFe@C nanocomposite catalyst through one-step solid state pyrolysis in an inert atmosphere.Through the characterization of the composition,morphology and crystal structure of the sample,it was found that:A large number of hydrophilic hydroxyl functional groups were found on the surface of graphite carbon in the preparation of carbon-coated nickel-iron alloy nanocomposite catalysts,which can effectively promote the catalytic reaction in liquid phase.When the catalyst was used for electrocatalytic hydrogen evolution(HER)under alkaline conditions,NiFe@C showed better electrochemical performance than commercial Pt/C,that is,j=10mA·cm-2 had a cross potential of 27.2mV,and showed higher stability.NiFe@C 's excellent electrochemical hydrogen evolution performance is due to the metal-like properties and high crystallinity of the alloy.By adjusting the metal ratio in NiFe-Sal LDHs,we can control the structure of NiFe@C material and improve the reactivity of the catalyst.In summary,this paper takes a cheap organic-inorganic layered bimetallic hydroxide as a single precursor,controllable reduction of layered bimetallic precursor,and one-step solid-state synthesis of multiple nanocomposite catalysts.The catalyst showed excellent performance in photocatalysis,electrocatalysis and photochemistry.The high-quality,high crystallinity,high dispersion,and efficient nanocomposite materials prepared by this method have potential application prospects in the fields of energy,environmental catalysis,and the like.