| To adapt to the evolution of the general trend of peak carbon dioxide emissions and carbon neutralization,as well as the globalization,electrification,sharing and intelligent transformation of the whole energy structure,terminal solutions represented by LIBs and fuel cells have gradually become the mainstream of the market.However,a single scheme can not meet the needs of high energy density and high-power density at the same time,so that these defects still limit its popularization and application.Therefore,the development of high-performance and long-life electrode materials and device systems has become a key research direction.Carbon aerogels and their derived materials,as one of the new materials in the twenty-first Century,have attracted much attention due to their unique structure and excellent electrochemical properties.With the deepening of the research,the potential of carbon aerogels in high-power energy storage devices and catalysts is becoming more and more important.Matching high-power supercapacitors with high specific energy fuel cells is expected to solve the defects of low energy density and low power density in the current scheme.This complementary scheme will be a potential competitor to replace fossil fuels.Carbon aerogels have stable self-supporting3D porous structure,which can be used as catalyst carriers for hydrogen source preparation of fuel cells,and can also be used as electrode materials for supercapacitors.Although CA material has many advantages,its high cost and complex preparation process still limit its popularization and application.In view of the existing problems in CA materials,the potential applications of carbon aerogels in energy storage and catalytic application scenarios are given through hetero atom doping,structural control and functional loading.The research results of dissertation are as follows:(1)Firstly,NCA microspheres with high N content and low specific surface area were obtained by using natural carbon materials as precursors.The synthesized aerogel microspheres were used as Na and K ion half-cell anode materials.The unique 3D porous structure of aerogels with high nitrogen content and the surface effect and storage mechanism of Na and K ions were studied.It was found that the nitrogen content of obtained NCA exceeded 10wt%,and reached the high level in the reported literatures.SEM and BET analysis showed that the materials have rich pores.Compared with conventional porous carbon and carbon aerogels,the NCA has a lower specific surface area,but for Na and K negative materials,it balances the rate characteristics and ICE demand.In addition,these three-dimensional tunnels provide a large number of ion binding sites and migration channels for the storage of K and Na.Due to the high nitrogen content and three-dimensional pore structure,NCA electrode has high K and Na storage capacity and excellent rate performance.Compared with K system,the capacity retention rate of NCA-Na half-cell is relatively low.(2)ANCA powders with high nitrogen content and high specific surface area were prepared by activated NCA microspheres precursors.The ANCA were used as EDLC electrode active materials,and the effects of aerogel electrodes on ionic storage and interface adsorption in aqueous electrolyte and three electrolyte solutions of Li,Na and K were studied.The results showed that the ANCA still maintained high nitrogen content,narrow pore size distribution and specific surface area of 1600 m~2/g.By studying the electrochemical characteristics of ANCA in aqueous electrolyte and organic electrolyte,it can be found that high nitrogen doped activated carbon-based aqueous supercapacitor,LIC,NIC and KIC have different performance and energy storage mechanism.(3)In order to obtain higher energy density,based on previous work research,ANCA with high surface area as positive electrode and low surface area HC as negative electrode were used to assemble full carbon Na and K ion asymmetric supercapacitors with assistance of ion pre-insertion technology.The diffusion effect of Na and K ions in aerogels as well as the influence of defect sites in aerogels on asymmetric capacitor were studied.The results show that there is a large performance gap between Na and K systems after the two electrodes are assembled into asymmetric capacitors.This shows that it is more difficult for K system to achieve the same performance in conventional carbonate electrolyte than in Na or Li system.The rapid charge storage mechanism of K ions in carbon materials is not clear,which may be very different from the established charge storage mechanism in comparable materials tested by Na or Li system,and needs to be further studied.(4)In view of the weak catalytic performance of pure carbon aerogels,a highly loaded and nitrogen doped Ni/Fe carbon aerogel composite catalyst was synthesized by using a melamine formaldehyde carbon aerogel as carrier under mild environment.The electrochemical process of base metal catalysts in HER,OER and overall water wplitting reactions were studied by the structure-activity relationship between the morphology,ECSA,electronic structure and electrocatalytic properties of the catalyst.The results show that the high loading catalyst can provide enough active sites for the catalytic process.At the same time,the high nitrogen content in aerogels can also improve the surface structure effect of catalysts during the catalytic process.(5)By combining the idea of multivariate alloy,the three-element catalyst was successfully carried into aerogel.The results showed that different proportions of Ni,Co and Mn elements could regulate the morphology,specific surface area and electronic structure of the catalyst.The aerogel catalyst was applied to HER and OER tests,and the results showed that it had good electrocatalytic performance.The calculations results show that the different element of Ni,Co and Mn possess synergistic effect.Through directed adjust the surface charge distribution of multi-metal catalysts,the more suitable surface electronic structure can be obtained. |
PDF Full Text Request