| The development of new energy storage and conversion materials and their preparation technology are the key to the development of sustainable new energy and its application in lithium/sodium ion batteries and fuel cells.Nowadays,traditional battery anode materials have problems such as low capacity and poor cycle stability,which are difficult to meet the development needs of lithium-ion and sodium-ion batteries.The electrocatalytic hydrogen production technology applied to fuel cells requires precious metal catalysts,which is difficult realization of low-cost and large-scale production.In recent years,a nano-array structure?NSA?based on a three-dimensional?3D?self-supporting structure and its combination electrode material have the advantages of high electrochemical activity,good stability and adjustable composition,and not required conductive additives and binders are expected to overcome the limitations of non-self-supporting electrode materials and their preparation processes,and are directly assembled in energy storage and conversion devices.Therefore,related research has received extensive attention.In this paper,using highly conductive carbon fiber cloth?CFC?as the substrate of3D self-supporting electrodes,a variety of new composite electrode materials composed of highly active nanomaterials have been designed,and a controllable preparation method of self-supporting electrode composite materials has been developed.The structure-activity relationship between their electrochemical properties and their microstructures and their active components,and their application to lithium/sodium ion batteries and electrocatalytic hydrogen evolution?HER?,shows good application prospects.The main research contents and results are as follows:1)Preparation and energy storage properties of molybdenum oxide self-supporting nanosheet array composite electrodeUsing CFC as the substrate,a simple solvothermal method is used to prepare vertically arranged high-density Mo S2 nanosheet arrays,and use a controlled thermal oxidation method to convert them into a highly active Mo O3-based nanoarray structure?Mo O3 NSA/CFC?.The electrochemical properties of the Mo O3 NSA/CFC self-supporting nano-array structure as a negative electrode material for lithium/sodium ion batteries were investigated,and the storage mechanism was proposed.It is found that as the negative electrode of lithium ion battery,the nano-array has high reversible lithium storage capacity and high cycle stability.For example,at a current density of0.1 m A cm-2,the surface capacity reaches 4.48 m Ah cm-2(equivalent to 1780 m Ah g-1);Cycling 200 cycles at a current density of 0.5 m A cm-2,the capacity retention rate is as high as 94%.The performance improvement is mainly attributed to the vertically distributed 3D array layered structure,which can provide a larger interface area around the electrolyte/electrode,which not only accelerates the rapid diffusion of Li+/Na+,but also effectively buffers the volume expansion and shrinkage effect that occurs during multiple cycles.In addition,applying it to a sodium-ion battery,at a current density of0.1 m A cm-2,the areal capacity is 2.5 m Ah cm-2(1621 m Ah g-1).2)The preparation of Fe2O3 modified Mo S2 nanosheet array and its energy storage propertiesMo S2 nanosheets can be applied to energy storage and conversion as a new two-dimensional nanomaterial,but Mo S2 itself has low lithium storage activity and poor conductivity,which further restricts its storage performance.On the other hand,free Mo S2 nanosheets are prone to agglomeration and overlap.Lead to a decline in electrochemical activity.In order to overcome the above shortcomings,this paper uses solvothermal method and self-sacrificial template method to directly grow carbon-doped Mo S2 nanosheet arrays on carbon fiber cloth,and modify the surface of the nanosheets with highly active Fe2O3 nanoparticles to prepare high-performance Fe2O3@C@Mo S2/CFC electrode.The performance test of the negative electrode of the lithium ion battery shows that the Fe2O3@C@Mo S2/CFC electrode can provide a capacity of 1541.2 m A h g-1 at 0.1 A g-1,and and a good capacity retention of 80.1%at1.0 A g-1 after 500 cycles.Fe2O3@C@Mo S2/CFC is used as the negative electrode material to apply sodium ion battery.At 0.5 A g-1,after 200 cycles,it still has a high reversible capacity of 889.4 m Ah g-1.3)Preparation of P@MOF/CNT composite self-supporting flexible electrode and its energy storage propertiesThe development of flexible electrode materials needs to solve the problem of low electrochemical performance and poor flexibility,especially the stability of electrochemical energy storage under high electrode deformation.Red phosphorus is one of the candidate materials for preparing flexible electrodes due to its high theoretical capacity and low cost.However,red phosphorus has poor conductivity and serious volume expansion during the cycle,which restricts its practical application.To solve these problems,we built a 3D layered structure network on a flexible conductive CFC substrate,and encapsulated the high-capacity red phosphorous material in a hollow carbon-based polyhedron derived from a metal organic framework?MOF?.In this layered structure,the MOF structure is designed to provide encapsulation space for the red phosphorus particles to alleviate the volume change of the red phosphorus during the cycle;a carbon nanotube?CNT?film is introduced between the MOF and the CFC to enhance the bonding force between the CFC and the MOF and improve the conductivity of the electrode material.The 3D self-supporting hierarchical structure is applied to lithium-ion batteries,showing excellent storage performance:at 0.1 m A cm-2,it has a high reversible capacity of 4.78 m Ah cm-2(1920 m Ah g-1),and has excellent cycle stability performance(73%and 69%capacity retention were obtained after 500cycles at current densities of 5 and 10 m A cm-2,respectively).4)Preparation of GQD@Co P self-supporting nano-array electrode and its HER performanceThe application of metal phosphide materials to HER electrodes needs to solve the problems of poor conductivity and easy decomposition in alkaline solvents.To this end,we prepared a self-supporting hierarchical material composed of graphene quantum dots?GQDs?uniformly supported on Co P nanosheet arrays.Under acidic and alkaline conditions,the application of this material as a HER catalyst has achieved good catalytic hydrogen evolution performance.The good catalytic performance mainly lies in the doping of N-doped GQD and its synergistic effect with the Co P nanosheet array.On the one hand,the addition of N-doped GQD not only improves the conductivity of the Co P material,but also provides more active sites for electrocatalysis.On the other hand,the design of the self-supporting hierarchical structure can maintain the stability of the material structure in alkaline media. |
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