Synthesis And Properties Of Transition Metal Phosphides Electrode Materials For Supercapacitors

With the rapid consumption of energy,has brought great confusion to people's economy,production and life and even affected health.Therefore,scholars around the world are committed to developing a new type of energy storage equipment to solve the problem of the non-renewable energy consumption.In this situation,scholars are striving to build a sustainable,cleaner and efficient energy storage equipment to solve this situation.The electrochemical energy storage(EES)has emerged and played an important role in energy storage equipment.In different EES,the supercapacitors(SCs)is a successful participant on the Ragone,in which supercapacitors with long cycling life,high power density,efficient charge transferfast,charge-discharge mechanism,easy synthesies process and low cost.In the past decades,supercapacitors have attracted great attentions in academic and industry.The choice of electrode materials determines the advantages and disadvantages of supercapacitors,so it is a great significance to develop a high-performance electrode material.In this thesis,combining domestic and foreign literatures,three experimental schemes were designed and three transition metal phosphide electrodes were synthesized with excellent properties.Meanwhile,using simple characterization techniques explore the materials morphology,chemical compositionnd and the electrochemical performance was also tested.The main work is summarized as follows:(1)Preparation and properties of Co P@Ni₂P/carbon paper core-shell nanosheets electrode materials for supercapacitorsIn this work,we successfully synthesized a hierarchical core-shell Co P@Ni₂P nanosheets on carbon paper,through a facile deposition and phosphating method.The optimized hierarchical core-shell Co P@Ni₂P nanosheets electrode shows a high specific capacitance of 2644 F g^-1at the current density of 1 A g^-1.Meanwhile,a three-dimensional(3D)?-Fe₂O₃grown on carbon paper was also synthesized as negative material by a hydrothermal and annealing method,which manifests an excellent performance of 539.2 F g^-1at 1 A g^-1.Besides,an asymmetric supercapacitor was assembled,using Co P@Ni₂P/carbon paper nanosheets as the positive electrode and?-Fe₂O₃/carbon paper as the negative electrode in 3 M KOH electrolyte,which exhibits excellent energy density of 48.5 Wh kg^-1with power density 793 W kg^-1.After 10000 cycles,the stability of the ASC reached 98.8%.The excellent electrochemical performance and outstanding cyclic stability of the asymmetric supercapacitor shows a great potential application in future energy storage devices(2)Preparation and properties of Ni-Fe-P electrode materials derived from Ni-Fe MOF for supercapacitorsThe Ni-Fe-P electrode materials grown on foamed nickel foam were successfully synthesized by solvothermal and phosphating processes.Electrochemical tests show that the electrode has the best performance,the specific capacitance reaches 1454 F g^-1at a current density of 1 A g^-1.In addition,in a 3 M KOH electrolyte,the asymmetric supercapacitor was constcucted with Ni-Fe-P/nickel foam as the positive electrode and AC as the negative electrode,the maximum specific capacitance of the ASC reached 136.5 F g^-1under the current density is 1 A g^-1.In addition,the energy density of the asymmetric supercapacitor is 48.5 Wh kg^-1with the power density of800 W kg^-1.(3)Preparation and properties of the two-dimensional Co-Mo-P/nickel foam Nanosheets electrode for supercapacitorsThe Co-Mo-P/nickel foam nanosheet electrode material grown on nickel foam was synthesized successfully by hydrothermal method and phosphating.By controlling the doping amount of molybdenum concentration,three electrodes with different molybdenum concentrations were prepared.The test results show that the electrode performance is excellent when the Mo concentration is 1 mmol,and the specific capacitance of Co-Mo-P-1/nickel foam reached 2012 F g^-1at a current density of 1 A g^-1.In addition,an asymmetric supercapacitor assembled with synthetic electrode materials exhibit excellent electrochemical performance,the maximum specific capacitance of ASC is 328.7 F g^-1when the current density is 1 A g^-1.In addition,the energy density of the ASC reached 116 Wh kg^-1with the power density of 800 W kg^-1.After 3000 cycles of testing,the stability of the ASC reached 93.4%.