Preparation Of Transition Metal Selenides And Their Studies On Sodium-ion Batteries And Electrolysis Of Water For Hydrogen Evolution

Transition metal selenides have the advantages of good electrical conductivity,stable structure,and low cost and are one of the most potential anode materials for sodium-ion batteries and catalytic materials for hydrogen evolution in water electrolysis.However,this material suffers from problems such as large volume expansion,polyselenide dissolution,and slow kinetics,which severely limit its commercial application.In order to solve the above problems,this thesis carried out a series of modifications on iron selenide-based materials,such as micro-nano structure design,carbon composite,heterostructure construction,etc.,which significantly improved the electrochemical performance of active materials,and its internal improvement mechanism The research was carried out,and the specific research contents are as follows:（1）The highly conductive 3D carbon network-encapsulated Fe₃Se₄ nanoparticles（Fe₃Se₄@NC@CNTs）were successfully prepared by freeze-drying method combined with in situ selenization method for sodium ion storage and water electrolysis for hydrogen evolution.The composite material exhibits a three-dimensional porous structure with uniform pore size distribution and a diameter of about 200 nm.The good pore structure ensures the high electronic conductivity and structural stability of the material.The superior electrochemical performance of Fe₃Se₄@NC@CNTs can be attributed to its unique three-dimensional porous network and heterostructure,which is well adapted to the volume change caused by the deintercalation of Na ions,shortens the ion transport path,and enriches the active site.These results may provide ideas for the development of high-performance sodium-ion batteries and advanced electrode materials for water electrolysis.（2）Sea urchin-like Co Se₂@Fe₃O₄@Fe₂O₃ composites were synthesized by hydrothermal method and in-situ selenization process using SiO₂ nanospheres as templates.The unique nanostructure provides fast electron/sodium ion transport paths and exhibits excellent structural stability,ensuring fast kinetics and long cycle life of Co Se₂@Fe₃O₄@Fe₂O₃ electrodes for sodium storage.Similar processes can be applied to the fabrication of various metal oxide/selenide electrode materials for high-performance Li/Na-ion batteries.（3）Highly conductive Fe₃Se₄ nanoparticles were encapsulated in nitrogen-doped 3D porous carbon matrix by a hydrothermal method combined with an in-situ selenization strategy to address the defects of large volume change and slow kinetics during Na ion de/intercalation.The interconnected three-dimensional porous structure provides space for the volume change of Fe₃Se₄and provides a fast transport path for ions.Furthermore,the carbon coating encapsulating Fe₃Se₄nanoparticles has excellent electrical conductivity and volume tension,ensuring fast kinetics and structural stability.This work highly highlights the potential application of iron-based metal selenides in Na-ion batteries.