Effective Construction Of Metal Phosphate And Its Application In Energy Storage And Conversion

Due to unique electronic structure,metal phosphides exhibit potential application values in the field of magnetics,catalyst and electrochemical energy storage and conversion,and attact much attention in recent years.However,there are some drawbacks limiting their practical application,such as harsh synthesis conductions,bad conductivity.Based on these problems,in this thesis,a series of composite materials loaded with island-like Ni2P,MoP quantum dots and sandwich-structrued Sn4P3 have been prepared with polypyrrole(PPy)hollow fiber as template under different synthetic routes,respectively.Then,bifunctional catalytic activities for both oxygen reduction reactions(ORR)and oxygen evolution reactions(OER),lithium oxygen batteries(LOBs)performances and anode performance of sodium ion batteries(SIBs)have orderly characterized and discussed in detail.1.With PPy hollow fiber as template,composite materials composed of hollow carbon fiber and island-like Ni2P nanoparticles(Ni2P@HCF)have been prepared via solution impregnation,carbonization and phosphorization under low temperature.Carbonization themperature is a main factor on ORR/OER catalytic performances.Rotating ring-disk electrode(RRDE)results show that NhP@HCF-900 has excellent ORR/OER bifunctional catalytic activity.The ORR initial potential is 0.0888 V(vs.Ag/AgCl),and the limited current density is 4.348 mA cm-2(1600 rpm),and a quasi-four electron reaction is obtained;Under an anodic current of 10 mA cm-2,the OER potential of Ni2P@HCF-900 is 0.715 V(vs.Ag/AgCl),which is lower 70 mV than that of commercial Pt/C electrocatalyst,and a better OER stability is also obtained.2.With PPy hollow fiber as template,N,P-codoped hollow carbon fibers loaded with highly dispersed molybdenum phosphide quantum dots(MoP QD@HCF)have been synthesized through hydrothermal reaction and phosphating process under high temperature.After a simple suction filtration process,a 3D self-supporting oxygen electrode without binder has been fabricated.The assembled LOBs shows excellent discharge/charge performances:high discharge/charge specific capacity(up to 6.75 mAh cm-2),low charge potential plateau(<3.85 V)and high rate capability(up to 0.4 mA cm-2).After characterizations of discharge/charge products under different conductions,and DFT(Density Functional Theory)calcaulation of MoP,we make an excellent interpretation about MoP QD on the performance of LOBs.3.With PPy hollow fiber as template,sandwich-structured C@Sn4P3@HCF composite materials have been prepared via solution impregnation,carbon coating,carbonization reduction and solvothermal phosphating,and evaluated as SIBs anode.After activation,a charge-discharge specific capacity of 224 mAh g-1 and coulomb efficiency over 99%have been obtained,and the as-prepared SIBs shows excellent rate capability and cycle stability.The typicl sandwich structure can effectively compensate volume change of Sn4P3 during the discharge-charge process.