| Due to the excellent mechanical,thermal,optical,electrical and chemical properties,carbon materials have been extensively studied.Since "carbon" has three different hybrid states,it can form carbon materials with different dimensions and distinct properties.For example,graphene with two-dimensional honeycomb structure exhibits a long spin lifetime and limited hyperfine interaction in addition to its high conductivity and surface area,which favor its potential applications in spintronics and biomedicine.The magnetism of this kind of linghtweight material makes it possible to design and synthesize suitable information memory devices,which is expected to replace silicon as the main raw material of new generation electronic devices.Moreover,graphene is considered as a potential material for the innovation of electrochemical energy storage devices,because of its large specific surface area,ultra-high conductivity,chemical stability and flexible pasticity.Different from the planar structure of graphene,it has been proved that 0D fullerenes(C60)with special cage structure have potential catalytic value in the field of non-noble metal energy catalysis due to its curvature and pentagon defects.In recent years,heteratom doping,especially nitrogen doping,can effectively regulate the physical and chemical properties of carbon materials.In basic physics,nitrogen doping can introduce magnetic moments.For intrinsically non-magnetic perfect graphene,the introduction and regulation of local magnetic moments to obtain room temperature(RT)ferromagnetism(FM)is the key to the application in spintronic devices.Our group has obtaind ferromagnetic graphene by fluorination followed by defluorination in situ doping of nitrogen,of which the ferromagnetic moment is up to 0.17 emu g-1 and the Curie temperature has been raised to 250.1 K.However,paramagnetism still dominates,and the ferromagnetic ratio is still very low(high up to about 13.5%).Thus,there is still a long way to RT application.In electrochemistry,nitrogen doping can influence the electron distribution and spin concentration of graphene,thus affecting the active regions on the surface of materials,which can directly participate into catalytic reactions.As a result,the electrochemical performance can be increased significantly,promoting the applications in the field of electrochemistry.However,graphene sheets are easy to be re-stacked during the preparation processs,which reduces the effective surface of materials not being fully utilized.Therefore,reasonable design and preparation of 3D graphene has become the goal of many researchers.Except for graphene,nitrogen doped 0D C60 are theoretically expected to be a promising candidate of non-noble metal catalysts for energy batteries,which has not been experimentally reported yet.In this paper,on the basis of our previous works,stable room temperature ferromagnetic nitrogen-doped graphene was obtained experimentally for the first time.And the designed nitrogen-doped 3D graphene network(GF-NG)structure and 0D C60 both show ideal electrochemical properties.The main research contents and results are as follows:1.The spherical difference electron microscopy(SDEM)shows that the as-prepared graphene by Hummers method has lots of large defects.The existence of vacancies can hinder the coupling between magnetic moments.Moreover,nitrogen tends to dope into these large defects and is non-magnetic,which greatly reduces the useful introduction efficiency of magnetism.In order to gain RT ferromagnetic graphene which can be applied in practice,we choose to adopt the perfect graphite as raw materials and finally obtain RT ferromagnetic graphene by the method of fluorination followed by defluorination in situ doping of nitrogen,when the nitrogen doping level is just 5.88 at.%.It greatly improves the effective magnetic introduction efficiency of nitrogen and the ferromagnetic ratio is high up to 32.5%,which further promotes the application of graphene in spintronic devices.2.To meet the demands of large specific surface area,high conductivity and abundant active sites for electrochemical properties,we designed and prepared 3D GF-NG structure.The 3D graphene foam(GF)skeleton with high conductivity penetrates and supports the nitrogen-doped graphene(NG)gel,which solves the problem of the collapse of the graphene and the reduction of effective specific surface area,thus forming a porous 3D structure with a specific area of 583 m2 g-1.Combing the rich active sites and high conductivity of NG gel,the problem,of which graphene can’t both own the high conductivity and large specific area,has been solved.The conductivity is 3.33 S cm-1 and the internal resistance is down to 0.4 Ω.Due to the synergistic effect between the GF and NG gel,the maximum specific capacitance can be up to 380 F g-1 in the supercapacitor.And it also affords the 3D GF-NG material excellent cycling stability,of which the capacitance still retains 93.5%of the initial value after 4600 times of charge/discharge at 5 A g-1.3.Nitrogen atoms were successfully doped into 0D fullerenes(0D C60)by fluorination followed by defluorination process and the cage-like structure was preserved.The experimental results show that the catalytic performance of C60(nitrogen doped C60:NC60;E1/2:0.76V,limit current:4.66 mA cm-2)is greatly improved after nitrogen doping,which is similar to the commercial Pt/C material(E1/2:0.80V,limit current:5.67 mA cm-2).And it shows better long-term operation stability than Pt/C.Contrastive experiments have proved that C60 treated by high temperature and the fluorination followed by defluorination process shows the best performance.And the NC60 is closest to the theoretical model C59N with the best catalytic ability.This indicates that the synergistic effects of high temperature repair,curvature,pentagon defects and nitrogen doping have greatly improved the catalytic performance of C60,which opens up a new way for the application of C60 in the field of energy catalysis. |
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