Preparation Of Graphene-based Nanocomposites And Their Application In Catalysis

Transition metals have an irreplaceable position in the field of catalysis and have been widely studied by researchers as a powerful alternative to noble metals,solving the problems of scarce earth content and high cost of noble metal catalysts.However,the transition metals themselves have the problems of few active sites,poor electrical conductivity and particle agglomeration,which limits the improvement of its catalytic performance.It has been found that the introduction of carriers with excellent conductivity can improve the catalytic performance by plenty studies,so it is very promising to design and synthesize highly active and selective transition metal-based materials by the above means.Since its creation in 2004,graphene has been the focus of scientific researchers.Graphene is widely used in many fields due to its unique two-dimensional structure and excellent electrical and optical properties.The huge surface area of graphene can well disperse the material and play a role in preventing material agglomeration.And by wrapping the material with an ultra-thin layer of carbon single atoms,the catalyst can maintain a good structure without collapse during the catalytic process,ensuring the stability of the material.Meanwhile,graphene has an efficient electron transport ability,which enhances the catalytic performance.Graphene oxide produced by the oxidation method has a large yield in a single batch.And the reduced graphene oxide can be obtained by a simple reduction method and many other advantages are widely used.In this paper,graphene obtained by oxidation method was used as a carrier.Graphene-based oxidized graphene-based nanocomposites were obtained by loading metal materials.And their applications in non-homogeneous catalysis and electrocatalysis were investigated,and the main research contents and results are as follows:（1）Graphene-loaded CoO nanoparticle（CoO/Graphene,CoO/G）catalysts were prepared by chemical reduction method.The microstructures were observed using XRD,XPS,SEM and other testing methods.After catalytic testing,CoO/G catalyzed the oxidation of cyclohexane with molecular oxygen as oxidant efficiently to produce KA oil.The yields and selectivities were 32.4%and 75.4%,respectively,which showed much higher catalytic performance and selectivity than other catalysts.And the presence of graphene makes the catalyst easy to be separated.And it has good stability and recyclability.（2）Nitrogen-doped oxidized graphene-loaded Fe₂N nanocomposites（Fe₂N/NGO）were obtained by a simple hydrothermal and calcination method.The huge specific surface area of graphene oxide was utilized to disperse the material uniformly on the graphene oxide surface,which prevented the activity deficiency caused by particle agglomeration.In addition,the nitrogen-doped graphene oxide has faster electron transfer rate,and the Fe₂N/NGO catalyst shows high catalytic activity in benzylamine coupling reaction.The tests showed that the catalyst has excellent stability.（3）FeS₂/GO composites were prepared by loading FeS₂ nanoparticles onto the graphene surface.And the surface structure of FeS₂/GO was studied by XRD,XPS,SEM and other microscopic means.Benefiting from the strong coupling effect at the interface,the catalysts showed excellent catalytic activity in acidic electrolyte(NH₃ yields of 78.6μg h^-1 mg^-1_cat.and Faraday efficiency of 4.70%in 0.1 M HCl).The comparative tests demonstrated that ammonia was produced from the reduction of nitrogen and that the catalyst was stable for a long time in acidic electrolyte.The excellent selectivity of the catalyst was confirmed by by-product testing of the electrolyte.