Hierarchical Construction And Electrochemical Performance Of One-dimensional Molybdenum Trioxide- Based Composites

As a potential electrode material in energy storage,MoO₃ has received more and more attention in supercapacitor applications in recent years.For example,the 1D nanobelt structure of MoO₃ has a more efficient electron transport path and a higher surface volume ratio.But the practical application for MoO₃ nanobelts has been limited due to the poor electrical conductivity,a low specific capacitance and slow faradaic redox kinetics of MoO₃.How to improve the electrochemical performance of MoO₃ has been one of the most attractive topics in scientific fields.In order to solve these problems,there are two effective methods that have been widely studied including coupling with other nanoparticles to increase its specific area and introducing good conductivity materials to improve its conductivity.Therefore,to obtain high-performance electrode materials,this paper proposes strategies of coating 1D MoO₃nanobelts with carbon materials and modifying 1D MoO₃ with TiO₂ and Ag nanoparticles.TiO₂/MoO₃ composites with uniform morphology and structure were prepared by a two-step hydrothermal method.The results of scanning electron microscopy and transmission electron microscope show that the TiO₂ nanoparticles are uniformly distributed on the surface of MoO₃ nanobelts to form heterostructure.The nanobelt has a length of about 2?m and a width of about 200 nm,and its surface is significantly roughened by the combination with TiO₂.The specific surface area of TiO₂/MoO₃ is77.307 m²/g,which is much larger than that of MoO₃ with 29.733 m²/g.It has been found that at a current density of 1 A/g,the specific capacitance of the composite is 141F/g,which is much higher than that of the pure MoO₃ electrode with 69 F/g and pure TiO₂ electrode with 21 F/g.After 2000 cycles,the TiO₂/MoO₃ electrode still remains about 77.5%of the highest capacitance.The C@MoO₃ composite was successfully synthesized by a green and efficient hydrothermal method.A series of material characterization tests were carried out.The The electrochemical results show that the specific capacity of the composite is 179 F/g at the current density of 1 A/g,which is much better than that of the MoO₃ electrode.The charge transfer resistance of the composite electrode?0.5??is much lower than that of MoO₃ nanobelts?1.423??,indicating that the composite improves the transfer rate of charge at the electrode/electrolyte interface and reduces the transfer resistance.In order to further increase the specific surface area and enhance the conductivity of MoO₃,the small size effect of Ag nanoparticles and their excellent electrical conductivity are used to improve the electrochemical performance of MoO₃.By investigating the mass content of Ag,it is found that the Ag@MoO₃ composite at the mass content of Ag of 8%has the best morphology and structure,and the corresponding electrochemical performance is also the best.The agglomeration and growth of Ag nanoparticles occurred on the surface of MoO₃ with the further increase of Ag quality,which affected the electrochemical properties of Ag@MoO₃ composites.The specific surface area of the composite is 103.699 m²/g,which is 3.48 times than that of MoO₃.When the current density is 1 A/g,the specific capacitance of 8%Ag@MoO₃ is 225F/g.The results of EIS show that the charge transfer resistance of the composite is much lower than that of the MoO₃.The specific capacitance retention of the composites is88.9%after 2000 cycles.