Study On Synthesis And Properties Of Several Molybdenum-based Oxides

With the emergence of environment degradation and global warming,energy crisis has attracted widespread attention.The development,transformation and storage of renewable energy have become the focus of research.Metal molybdenum has attracted much attention and invested a lot of research because of its various oxidation states,high electrical conductivity,high temperature resistance and corrosion resistance.It has promoted the development of molybdenum-based oxides greatly and discovered that molybdenum-based oxides have great application potential in many fields.For example,the double perovskite molybdenum oxide is considered as a potential material in magnetic refrigeration technology due to its magnetocaloric effect in external magnetic field;the molybdenum-based materials such as molybdenum oxide and metal molybdate are ideal electrode materials for the research of supercapacitors…In this research,Sr₂FeMoO₆,Sr_1.8Eu_0.13Ba_0.07FeMoO₆,CoMoO₄ and NiCoO₂/CoMoO₄ materials were selected as the research object,and they are prepared by high-temperature solid reaction method and hydrothermal reaction method.The basic physical properties of the prepared materials were analyzed by XRD,SEM and other testing techniques.At the same time,the magnetic properties and magnetocaloric effect of Sr₂FeMoO₆ and Sr_1.8Eu_0.13Ba_0.07FeMoO₆ compounds were investigated by the methods of magnetic properties correlation analysis.The magnetic properties and magnetocaloric effect of Sr₂FeMoO₆and Sr_1.8Eu_0.13Ba_0.07FeMoO₆ compounds were analyzed.Furthermore,the preparation and electrochemical properties of CoMo O₄ and NiCo O₂/CoMoO₄ compounds were investigated by using hydrothermal reaction method,cyclic voltammetry,galvanostatic charge and discharge,electrochemical impedance spectroscopy.The main contents and results are shown as follow:?1?The Sr₂FeMoO₆ and Sr_1.8Eu_0.13Ba_0.07FeMoO₆ compounds are successfully synthesized by high-temperature solid reaction method.The XRD results show that all samples are single phase,and the degree of Fe/Mo ordering in Sr_1.8Eu_0.13Ba_0.07FeMoO₆ compound is increased from 89.3%for Sr₂FeMoO₆ to92.6%.Then,the magnetic properties and magnetocaloric effect of two samples were analyzed.The analysis results of the two samples showed that Sr_1.8Eu_0.13Ba_0.07FeMoO₆ has greater saturation magnetic moment and Curie temperature than that of Sr₂FeMoO₆.The maximum isothermal magnetic entropy change of Sr_1.8Eu_0.13Ba_0.07FeMoO₆ reaches to 0.76 J/kg?K from 0.50 J/kg?K of Sr₂FeMoO₆.It indicated that Sr_1.8Eu_0.13Ba_0.07FeMoO₆ has a better magnetocaloric effect than that of Sr₂FeMoO₆.Totally,Sr₂FeMoO₆and Sr_1.8Eu_0.13Ba_0.07FeMoO₆ all have great magnetocaloric effect,which have great application potential in the field of magnetic refrigeration technology.?2?The CoMoO₄ samples,which marked as CMO-1,CMO-4,CMO-8,CMO-12 and CMO-24 were successfully synthesized by hydrothermal reaction method.The effect of different reaction times on the electrochemical performance of CoMoO₄ samples was investigated by electrochemical analysis method.Cyclic voltammetry and galvanostatic charge and discharge analysis results show that both at the same scan rate and at the same current density,the specific capacitance of CMO-12 is greater than that of the other four electrodes.In addition,the resistance of CMO-12 system is the smallest could be obtained from electrochemical impedance spectrum.Analysis results show that the optimal reaction time for CoMoO₄sample preparation is 12 hours,CMO-12 has the best conductivity and electrochemical performance.?3?The NiCoO₂ samples,which marked as NCO-4,NCO-8,NCO-12 and NCO-24 were synthesized by hydrothermal reaction method at different reaction times.Their electrochemical analysis results show that NCO-12 has the best electrochemical proformance.Then,Ni CoO₂/CoMoO₄ composite material was obtained by compounding NiCoO₂ into CoMoO₄ through hydrothermal reaction method.The electrochemical properties of NiCoO₂/CoMoO₄ composite material were investigated in KOH electrolytes with concentrations of 1 mol/L,2 mol/L,and 4 mol/L.Analysis results show that the electrochemical properties of NiCo O₂/CoMo O₄ composite material are better than that of pure CoMoO₄ material.This shows that the electrochemical properties of CoMoO₄ materials were effectively improved by the addition of NiCoO₂ materials.Therefore,it is feasible to improve the electrochemical properties of electrode materials by combining two materials.