The Composite Design Of Molybdenum Dioxide Based Electrode Material And Its Electrochemical Energy Storage And Electrocatalytic Oxygen Evolution Performance

With the implementation of carbon neutrality,China is gradually forming an energy supply structure as multiple coexistence and multi-energy complementary,which includes supercapacitor and electrocatalytic water splitting.Electrode materials play a decisive role in these energy devices.Mo O₂has a special distorted rutile structure,and its high conductivity,excellent chemical stability and extremely high theoretical capacitance value have attracted attention.In the process of ion deintercalation,the volume of Mo O₂changes greatly,the cycle stability is poor,and it is difficult to give full play to its superior performance as an electrode material in the field of supercapacitors and electrocatalysis.This paper is aimed at improving the poor cyclic stability of Mo O₂and investigating the unique growth mode of Mo O₂through composite design to achieve optimization of electrochemical properties.It is proposed to grow Mo O₂nanoparticles on the surface of carbon cloth（CC）by in-situ reaction;form a homogeneous Mo O₂-coated homogeneous shell on carbon foam（CF）by hydrothermal reaction;synthesize Mo O₂/three-dimensional carbon composites by endogenous-exogenous method.The electrochemical performance of the prepared electrode materials was characterized,and their application prospects in energy storage and electrocatalytic water splitting were discussed.This study explores new synthesis paths and provides implementation methods for material utilization.It shows reference value for the structural design,process optimization and performance improvement of Mo O₂/C composites,and for their development of energy storage devices and catalytic application.The main contents are as follows:The Mo O₂@CC composites were prepared by in situ growth of uniformly dispersed Mo O₂nanoparticles on CC through the agglomeration and deposition of nanoclusters in molybdenum blue colloidal solution.When the amount of molybdenum blue（molybdenum concentration of0.007 M）is 3.5 m L,Mo O₂nanoparticles in the Mo O₂@CC composites possess good crystallinity and uniform dispersion.The prepared composites have an overpotential of up to 1056 m V in a neutral electrolyte（1 M Na₂SO₄）and could be operated stably in a wide potential window of 2 V.After 5000 cycles of charge and discharge at a current density of 10 m A cm^-2,the capacitance still reaches 90.41%of the initial capacitance.When an asymmetric supercapacitor was assembled,after 2500 cycles of charge and discharge at a current density of 10 m A cm^-2,the capacitance of the assembled device can be increased to 130%of the initial state,showing excellent stability.This is attributed to the homogeneous dispersed Mo O₂nanoparticles improving the ion migration rate of the composite during cycling.In the field of electrocatalysis,the Mo O₂@CC-35 catalyst only needs an overpotential of 347.4 m V to drive water splitting and has potential for electrocatalytic applications.This work provides a new synthesis path for preparing Mo O₂matrix composites with high cycle life.By a hydrothermal method,Mo O₂is grown as homogeneous shell on the network skeleton of carbon foam（CF）to prepare Mo O₂@CF composites,to improve the energy storage performance of Mo O₂-based composites.When 0.35 g of ammonium heptamolybdate（AHM）was added,the prepared Mo O₂@CF-7 exhibits optimal electrochemical performance.Using 1 M Na₂SO₄as the electrolyte,the specific capacitance of Mo O₂@CF-7 is 211 F g^-1when the current density is 1 A g^-1.After 9000 charge-discharge cycles,the composite still has 95%of the initial capacitance(current density of 3 A g^-1).An asymmetric supercapacitor assembled by Mo O₂@CF-7 with a potential window of 2 V can still maintain 88.7%of the initial capacity after4200 cycles of charge and discharge at a current density of 10 A g^-1.When the power density is1002 W kg^-1,its corresponding energy density can reach 13.5 Wh kg^-1.The oxygen evolution test results show that the overpotential of Mo O₂@CF-7 is only 335.4 m V in 1 M KOH,which is lower than that of commercial Mo O₂catalysts.The compounding of Mo O₂with carbon foam in the form of this homogeneous shell increases the area of electrochemical reaction and leads to a significant improvement in electrochemical performance,which may provide a reference for the development of bifunctional materials.In order to obtain Mo O₂matrix composites with excellent performance in the fields of electrochemical energy storage and electrocatalytic oxygen evolution.Three-dimensional carbon（3DC）based endogenous-exogenous Mo O₂composites were synthesized by a two-step process using the phase transition of molybdenum oxide.Among them,MC-15 exhibits the most outstanding electrochemical performance,with a specific capacitance as high as 411.4 F g^-1in Na₂SO₄.The capacitance of the electrode remains 94.1%of the initial after 5000 cycles of charge and discharge.The asymmetric supercapacitor using this material as the negative electrode and Mn O₂@CC as the positive electrode can achieve an energy density of 14 Wh kg^-1when the power density reaches 802 W kg^-1.The specific capacitance retains 84.9%of the initial state even after 2500 cycles.In addition,MC-15 exhibits low overpotential and Tafel slope in alkaline electrolyte through electrocatalytic oxygen evolution test.This is attributed to the fact that the endogenous-exogenous grown Mo O₂effectively avoids agglomeration while providing sufficient electrochemical reaction sites,it lays a certain research foundation for the subsequent dual-function application of Mo O₂matrix composites.