| The global economy and society are transforming to control environmental pollution and realize low-carbon development.The energy structure also needs to keep up with the trend of clean,low-carbon and digital times,and effectively boosts technological innovation and transformation.Electrochemical energy storage and conversion technologies are the key to the efficient and environmental protection utilization of renewable clean energy,which can efficaciously alleviate the world energy crisis.Electrochemical power supply is a momentous tool for energy storage and conversion,among which lithium-ion battery with advantages of high energy density,long cycle life and environmental friendliness has entered the stage of booming application and development in the field of portable electronic equipment and new energy vehicles,and it is of great strategic significance to develop new lithium-ion battery anode materials with high capacity and long cycle performance.The control of composition,structure and functional properties of active materials are critical to the construction of highpowered lithium-ion battery electrode materials,which are essential to heighten the reaction kinetics and structural stability of electrode materials.In addition,note that hydrogen energy as a secondary energy with high energy density and zero pollution,is an indispensable part of a clean,low-carbon,safe and efficient modern energy system.Electrolyzed water is the key technology of green and sustainable hydrogen production,and electrocatalyst is of significance toward reducing reaction overpotential and improving energy conversion efficiency.Handicapped by shortage and high price of Pt based catalysts with high efficiency,it is in urgent need to develop predominant hydrogen evolution electrocatalysts with low cost and high activity utilization.Based on the above,this paper takes construction and application of highefficiency lithium-ion battery anode materials and electrocatalyst for hydrogen evolution reaction,a series of Mo-based nanocomposites were constructed aiming at improving charge transfer,electron transportation,catalytic activity and structural stability of nano materials,and internal rules of microstructure and properties were revealed.The main contents of the thesis are as follows:A brand-new idea of improving lithium storage performance of Mo-based anode nanomaterial by multi-component co doping was proposed.Based on the simultaneous in-situ chemical conversion process of metal ions and nano confinement carbonization of organic ligands in metallic organic frameworks,MoO2-Cu@PC and Mo0.8W0.2O2-Cu@PC nanocomposites were constructed using metal organic frameworks as templates.For MoO2Cu@PC,three-dimensional carbon matrix can be capable of preventing agglomeration and pulverization of MoO2,and copper metal embed into the carbon matrix to form a high conductivity network,which become an ideal buffer for buffering volume strain of active substances during the cycle process,it could be stable for 200 cycles at current density of 1 A g-1 and provided with a specific capacity of 370 mA h g-1 at 10 A g-1.For Mo0.8W0.2O2-Cu@PC,introduction of Mo0.8W0.2O2 solid solution further improved transport kinetics of lithium ion,W doping nicely improved diffusion coefficient of lithium ion,and accelerated conversion process of MoO2 active substance,and three-dimensional carbon framework embedded with conductive copper metal particles enhanced the overall conductivity and structural stability.When employed as anode for lithium-ion batteries,Mo0.8W0.2O2-Cu@PC nanohybrids exhibited ultralong cycle life for 2000 cycles at high rate of 2 A g-1 and 5 A g-1 with high volumetric capacity of 2390 mA h cm-3.which is 2-3 times that of graphite.?-MoC/MXene/C nanocomposite electrode materials were constructed by in-situ selfassembly strategy.MXene was conducive to improving electrode conductivity,riveting molybdenum carbide nanoparticles and accelerating pseudo capacitance behavior for lithium storage.The synergistic effect among ?-MoC nanoparticles with excellent conductivity,high density,high lithium storage capacity,stability and MXene,PVP-derived carbon desirably accelerated the electrochemical reaction process and achieved the fast and stable lithium storage process.Using MXene instead of acetylene black as electrode conductive additive can make the more conductive electrode,thinner electrode film,faster redox conversion mechanism,and the capacity retention rate at 10 A g-1 and 20 A g-1 increased by 37-40%,which can circulate 5500 times stably with the competitive volume capacity of 1560 mA h cm-3 at 10 A g-1.The Pt1-Mo2C-C nanocomposites featured by three-dimensional carbon matrix supported Mo2C nanoparticles dispersing atom-scale Pt was constructed by using polyoxometalates encapsulated in metal organic frameworks as precursors.The atom-scale Pt effectively improves utilization of noble metal atoms.The interaction between monoatomic Pt and Mo2C impressively promoted utilization of active sites,likewise adsorption and activation of water molecules,and acceleration of electron migration.When applied for electrocatalytic hydrogen evolution reaction,the overpotential of Pt1-Mo2C-C at 10 mA cm-2 in 1 mol L-1 KOH was only 155 mV,and mass activity was 7 times higher than that of commercial Pt-C.Thanks to the extensibility of catalyst preparation,onset potential of synthetic Ru1-MoC-C was only 4 mV with only 100 mV at 10 mA cm-2,and specific activity achieved 40 times that of Pt-C.From the viewpoint of utilization of two-dimensional defect rich carbon materials for dispersing and anchoring nanoparticles,a universal strategy for constructing ultrasmall molybdenum carbide nanoparticles supported single atom was proposed.The Ru1-MoC-NC structure with atom-scale Ru dispersed on MoC nanoparticles anchored on N-doped conductive carbon sheets was realized by high temperature carbonization.The results show that N-doped carbon matrix could ensure the uniform dispersion of molybdenum carbide nanoparticles and accelerate the process of charge transfer and mass transfer.Monoatomic dispersed Ru significantly improved utilization of precious metals,the electronic synergy between MoC and monatomic Ru encouragingly facilitated water adsorption and activation capacity,optimized the hydrogen adsorption strength.When applied for the electrocatalytic hydrogen evolution reaction,overpotential of Ru1-MoC-NC electrocatalyst was only 78 mV at 10 mA cm-2 in 1 mol L-1 KOH.The overpotential to achieve 50 mA cm-2 was even lower than that of commercial PtC,and the mass activity was 15 times that of Pt-C. |
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