Synthesis Of Cobalt And Iron Modified Nitrogen Doped Carbon-based Electrocatalysis For Oxygen Reduction

As the world's environmental pollution and the global traditional fossil energy crisis are becoming more and more serious,the development of efficient,clean and sustainable energy equipment is imminent.As a promising clean and sustainable energy power equipment,the fuel cell can transform chemical energy directly into electric energy,which has attracted the attention of the researchers.However,the electrochemical sluggish kinetics process of cathodic oxygen reduction reaction,seriously reduced the fuel cell efficiency.Platinum?Pt?base catalyst has excellent ORR electrocatalytic activity,but its high cost and poor stability severely hinder the popularization and application of fuel cell.Based on the above questions,in this paper,a low cost and environmentally friendly nitrogen doped carbon-based material was selected as the research object,and the abundant cobalt and iron were used to further improve the electrocatalytic activity.A series of nitrogen-doped carbon and iron-cobalt metal composite electrocatalysts with different structures were designed and synthesized.The influence of the microstructure and chemical composition of the materials on the ORR electrocatalytic activity was systematically explored,and the following main results were obtained:?1?A two-dimensional flake-like structured N-doped ordered mesoporous carbon nanosheet,in which Co nanoparticles are supported?Co/N-OMCNS?was fabricated by Co²⁺-complex and self-assembly method.The bicontinuous and uniform mesopores not only can promote proton transport efficiency,but also can facilitate the deposition of high density Co-N actives.Based on the synergistic catalytic effect of Co and N,Co/N-OMCNS prepared at 800°C exhibited the best ORR catalytic activity.?2?Nitrogen doped hollow carbon rods supported with Co₂P nanoparticles?Co₂P/N-HCR?were synthesized by high-energy ball milling and successfully used as ORR electrocatalysts.The important role of microscopic morphology,Co₂P nanoparticles and N-doping in enhancing ORR catalytic activity were also systematically explored.The Co₂P/N-HCR obtained at 750°C possesses the comparable electrocatalytic activity to that of commercial Pt/C.?3?Uniform nitrpgen-doped mesoporous carbon microspheres supported with Fe₃O₄nanoparticles?Fe₃O₄/N-MCS?were fabricated by using the rapid polymerization reaction between ferric ammonium citrate and hydroxymethylated melamine.The effect of the Fe content on the structure and composition were analyzed.The important role of the introduction of Fe species in improving the ORR electrocatalytic activity for N-MCS was also explored.The Fe₃O₄/N-MCS synthesized 800°C has superior ORR catalytic activity than that of Pt/C.?4?In order to obtain more excellent ORR catalytic activity,a hollow core-shell structured carbon carrier with rich porous surface was first constructed by using a sol-gel-hydrothermal method,then the nitrogen-doped hollow core-shell carbon spheres supported with Fe₃O₄ nanoparticles?Fe₃O₄/N-HCSC?were prepared under the action of melamine and Fe³⁺.The unique hollow core-shell hierarchical structure combined with rich pores can not only introduce high-density Fe and N active materials on the HCSC,but also promote the proton transmission efficiency during the reaction,thereby giving the Fe₃O₄/N-HCSC a more outstanding ORR performance than that of Pt/C.?5?A two-dimensional lamellar structured nitrogen-doped carbon nanosheets,in which Fe₃C nanoparticles are encapsulated?Fe₃C/N-CNS?was synthesized by high temperature pyrolysis and acid leaching,using dicyandiamide and iron-tannic acid complexes as solid phase precursors.The influence of pyrolysis temperature on the chemical composition,microstructure and ORR catalytic activity for Fe₃C/N-CNS was systematically analyzed.The Fe₃C/N-CNS obtained at 800°C possesses outstanding ORR catalytic activity not only in alkaline,but also in acidic and neutral media.