Preparation And Electrochemical Performance Of Fe₂MoC And Its Composites As Electrode Materials For Supercapacitors

Bimetallic carbides with high electrical conductivity,chemical stability,and rich redox reactions have aroused wide attention for energy-storage applications.In this paper,the bimetallic carbide Fe₂MOC is the main research object.Fe₂MOC particles and Fe₂MOC fibers are prepared by hydrothermal method and electrospinning,respectively.The high conductivity and large specific surface of Fe₂MoC endow it excellent rate performance and cycle stability.The transition metal oxide NiCo₂O₄ has high capacitance performance,but the low conductivity limits its rate performance and cycle stability.Therefore,the Fe₂MOC particles and NiCo₂O₄ nanotubes,Fe₂MOC fibers and NiCo₂O₄ nanosheets are combined to obtain Fe₂MoC/NiCo₂O₄ electrode material with high specific surface area,specific capacitance,rate performance and cycle stability.?1?The Fe₂MoC nanoparticles were prepared by hydrothermal method and their electrochemical properties were systematically studied.The results show that the Fe₂MoC nanoparticles exhibit the best electrochemical performance with acidified chitosan as carbon source at a hydrothermal temperature of 180 ? and a holding time of 18 h.At a current density of 0.5 A/g,the specific capacitance reaches 158.4 F/g.When the current density increases to 10 A/g,the specific capacitance is 134.0 F/g.The rate performance is as high as 84.6%,and the capacitor retention of 73.3%after 1000 cycles.In the ASC device,the energy density reaches 8.5 Wh/kg at a power density of 145 W/kg,indicating that the Fe₂MoC nanoparticles have excellent electrochemical properties and is a promising electrode material.?2?NiCo₂O₄ nanotubes and Fe₂MoC/NiCo₂O₄ composite electrode materials were prepared by electrospinning method,and the effects of pre-oxidation temperature on their morphology and electrochemical properties were investigated.The results show that the Fe₂MOC/NiCo₂O₄ composite has a one-dimensional tubular structure and the Fe₂MoC particles are uniformly distributed within the NiCo₂O₄ nanotubes at a pre-oxidation temperature of 250 ?.Fe₂MoC/NiCo₂O₄ exhibits higher electrochemical performance than Fe₂MOC particles or NiCo₂O₄ nanotubes.At a current density of 1 A/g,the specific capacitance of Fe₂MoC/NiCo₂O₄ reaches 722.7 F/g.When the current density increases to 40 A/g,the specific capacitance is 611.4 F/g,and the capacitance retention rate is 78.6%.After 2000 cycles,the specific capacitance retention is still 73.4%.In addition,in an ASC device,the energy density reaches 22.5 Wh/kg at a power density of 150 W/kg.?3?The Fe₂MOC fibers were prepared by electrospinning method,and the effects of carbonization temperature and heating rate on its synthesis and electrochemical properties were investigated.Studies have shown that the Fe₂MoC nanofibers obtained at a carbonization temperature of 800 ? and a heating rate of 5 ?/min exhibit excellent electrochemical performance.At a current density is 1 A/g,the specific capacitance reaches 347.8 F/g.When the current density increases to 40 A/g,the specific capacitance is 316.5 F/g,and the rate capability is as high as 91%.The specific capacitance retention is still 85.6%after 5000 cycles.In the button type ASC device,the energy density reaches 14.5 Wh/kg at a power density of 300 W/kg,and the capacitance retention rate is still 93%after 5000 cycles.?4?Fe₂MoC/NiCo₂O₄ composites were prepared by hydrothermal method using Fe₂MoC nanofibers as carrier,and the reaction temperature on morphology and electrochemical properties were investigated.NiCo₂O₄ nanosheets grow uniformly along the Fe₂MoC fibers at a hydrothermal temperature of 180 ?,which increases effectively the specifc surface area of the electrode material?295.3m2/g?,and provides more acti-ve sites for electrochemical reactions.The results show that at a current density of 1 A/g,the specific capacitance of Fe₂MoC/NiCo₂O₄ reaches 1303 F/g.When the current density increases to 20 A/g,the specific capacitance is 892.5 F/g,and the rate capability is 68.5%.After 10,000 cycles,the specific capacitance can still maintain 53%.In addition,when the power density of the ASC device is 300 W/kg,the energy density is 70.2 Wh/kg.