Preparation Of Transition Metals/N-doped Carbon Composites And Their Applications In Supercapacitors And Zinc-air Battery

Carbon materials,which show excellent electrode conductivity,thermal stability and electrochemical activity,have attracted widely attention.Carbon materials can be used as electrode materials,which have broad application prospects in energy storage and transformation fields,such as supercapacitors and zinc-air batteries.Supercapacitors are a new and efficient energy storage device with high power density,long-term cycle stability and fast charge-discharge performance.Zinc-air battery is an emerging energy device,in which zinc and activated carbon are used as the negative and,positive electrode to generate energy through the redox reaction between zinc and oxygen,respectively.The properties of the supercapacitors and zinc-air batteries are determined by the electrochemical activity and stability of electrode materials.How to obtain electrochemically active electrode materials is a key problem in the field of supercapacitors and zinc-air batteries.In this work,electrode materials with high electrochemical activity and stability were prepared by combining carbon materials with pseudocapacitive materials or heteroatom doping,including transition metal oxides,nitrogen atom doping and metal-nitrogen co-doping.The obtained carbon materials were applied and studied as electrode materials in supercapacitors and zinc-air batteries.The main research contents and conclusions are as follows:?1?Preparation of the polypyrrole tubes derived N-doped carbon nanotubes@manganese dioxide nanosheets composites and their applications in supercapacitorsBased on the rapid redox reaction between manganese acetate and potassium permanganate,the N-doped porous carbon nanotubes derived from polypyrrole tubes were used to in-situ grow MnO₂ nanosheets to prepare N-CNTs@MnO₂ under different temperature.The prepared N-CNTs@MnO₂ showed good electrical conductivity and high specific surface area.Due to the synergistic effect between the N-CNTs and MnO₂ nanosheets,the N-CNTs@MnO₂-800 exhibited excellent pseudo capacitance.When the current density is 1 A g^-1,the N-CNTs@MnO₂-800 released specific capacitance up to 219 F g^-1;While with the current density of 5 A g^-1,N-CNTs@MnO₂-800 exhibited good rate capability and long-cycle stability.?1?Synthesis of bimetal?Co,Fe?-nitrogen co-doped porous carbon fiber and application in zinc-air battery.The fibers,spinning by the solution mixed by cobalt-based zeolite imidazole framework?ZIF-67?containing iron-coordinated ionic liquid?IL-Fe?and polyacrylonitrile,was carbonized at different temperature to prepared Co/Fe-N-CFs.ZIF-67 and IL-Fe were used to provide the sources of cobalt,nitrogen and iron,nitrogen,respectively.It was found that Co/Fe-N-CFs-800 with optimal pore structure and abundant catalytic activity sites showed good catalytic performance in the process of oxygen reduction reaction?ORR?.Its initial potential and half-wave potential were 0.951 and 0.852 V,respectively,which are better than commercial Pt/C catalysts?0.930 and 0.830 V?.In addition.Co/Fe-N-CFs-800 based zinc-air batteries showed good rate performance and cycling stability.