Research On The Preparation And Catalytic Performance Of Cobalt,Iron/Graphene Composites

Fuel cell plays an important position in today's society.The noble metal material based on platinum(Pt)is the ideal catalyst for oxygen catalytic reduction(ORR)on the cathode of fuel cell.Because of the high price of precious metals and rare reserves limit.Therefore,it is necessary to develop low cost,durable and efficient catalysts to replace expensive rare noble metals(such as Pt,Au,Pd)catalysts in order to overcome the slow oxygen catalytic reduction(ORR)reaction process.In this dissertation,nanocomposites were prepared on graphene with cobalt and iron metal oxides,and the microstructure and electrochemical properties of nanomaterials were studied.In this dissertation,cobalt oxide/multilayer graphene composites were prepared by hydrothermal method.The properties of cobalt oxide/graphene nanomaterials with different cobalt precursors addition were studied.The microstructural characterization of Co3O4 nanoparticles showed that the size of Co3O4 nanoparticles was about 4 nm on the surface of graphene,and the Co3O4 nanoparticles with different distribution densities and morphology were obtained with the increase of cobalt reaction precursors.The results show that when the amount of cobalt tetroxide is 99.9mg,the oxygen catalytic reduction ability is the strongest,the starting voltage of the sample is-0.18V(vs Ag/AgCl),the electron transfer number can reach 3.87,which is close to the platinum nanoparticles.In this dissertation,iron oxide/multilayer graphene composites were prepared by hydrothermal method.The properties of cobalt oxide/graphene nanomaterials with different iron precursors addition were studied.The characterization of the microstructures of the samples shows that the size of the iron oxide nanoparticles with graphene indicates that the particle size of the iron oxide nanoparticles with different distribution densities and morphology is 5 nm.The results show that when the amount of ferrous chloride is 60 mg,the oxygen catalytic reduction ability of the sample is the strongest.The starting voltage of the sample is-0.31V(vs Ag/AgCl).The number of electron transfer can reach 3.79.In this dissertation,cobalt-iron bimetallic oxide/multi-layer graphene nanocomposites were prepared by hydrothermal method.The properties of cobalt-iron bimetallic oxide / graphene nanomaterials with different reaction time were studied.The nanocomposites were make up by multilayered graphene and cobalt-iron nanoparticles.The composite materials are lamellar graphene and metal nanoparticles.When the reaction time is 1 hour,the cobalt-iron bimetallic oxide is a sheet,and the average sheet thickness is 8 nm.As the reaction time increases,particulate oxides appear around the lamellae.The electrochemical test of the sample results in the following conclusions: When the reaction time is 10 hours,the starting voltage of the sample is-0.38V(vs Ag/AgCl)and the electron transfer number in the oxygen reduction process is 3.85.