Controllable Synthesis And Electrochemical Applications Of Prussian Blue Analogs And Their Derived Materials

The over-reliance on fossil fuels has led to the plundering of the weak countries by the powers.The continuous increase in carbon emissions has led to a more serious greenhouse effect in our country.The evolution of sustainable and neat resource has become a vital link to alleviate this major problem.The demand for novel storage device is ever increasing,motivated by electronic vehicles,portable devices and large-scale grids.Around 2000,with the help of nanomaterial technique,the discipline of materials engineering had stood out,and seized the opportunity for the rapid rise of new energy.Nano-material technique has deeply accelerated the evolution of novel energy basic devices such as new secondary batteries and supercapacitors.Among them,electrochemical supercapacitors have high specific power,long-term durability and rapid charge and discharge characteristics,which have emerged in the emerging new energy industry.In this paper,Prussian blue analogues doped with different metal molar and a metal-organic framework material ZIF-67 were prepared.The PBA with better performance is compounded with ZIF-67 as the electrode material for supercapacitor.It is mainly divided into the following three parts:(1)Controlling the molar ratio of nickel to cobalt elements,Ni1.5Co0.5Fe-PBA and Ni0.5Co1.5Fe-PBA nanocubes with different contents of nickel and cobalt were prepared via a co-precipitation way at normal temperature.PBA combined with bimetallic elements has a large specific surface area,rich active sites,easy to fully react with the electrolyte and all exhibits favorable performance.The specific capacitance of Ni1.5Co0.5Fe-PBA material in 3 M KOH solution is 2305 F g-1,which still maintains 92.67%of the original capacitance after 2000 cycles.Ni0.5Co1.5Fe-PBA has a capacity retention rate of 81.35%with specific capacitance of 1074 F g-1 at 0.5 A g-1.As a aqueous device,when the specific power is 1188 W kg-1,the maximum specific energy of Ni1.5Co0.5Fe-PBA//AC is 40.5 Wh kg-1;Ni0.5Co1.5Fe-PBA//AC,when the specific power is At 1305 W kg-1,the maximum specific energy is 83.4 Wh kg-1.In addition,controlling the ratio of doped metals is a way to explore versatile and more efficient high-performance PBAs.(2)Ni2Fe-PBA and hollow Co2Fe-PBA were synthesized via a facile co-precipitation way around 25? by separately controlling the molar mass of the transition metals nickel and cobalt.Hollow-structure nanomaterials have rich active sites and a thinner shell,which is easy to fully react with the electrolyte and ion penetration,making the performance of Co2Fe-PBA in supercapacitors far higher than Ni2Fe-PBA.At a current density of 0.5 A g-1,the specific capacitance of Co2HCFe even reached 2526 F g-1 under alkaline conditions,and maintained a capacity retention rate of 90.25%after 2000 cycles.Ni2Fe-PBA has a capacity retention rate of 75.46%with specific capacitance of 275 F g-1.In addition,for Ni2Fe-PBA//AC and Co2Fe-PBA//AC water-based devices,when the specific power is 1242 W kg-1,their maximum specific energies are 22.2 W h kg-1 and 53.8 W h kg-1,respectively.(3)We selected the PBAs with the best performance in the first two chapters that only doped with cobalt,skillfully used the MOF material ZIF-67 rich Co2+to react with K3[Fe(CN)6]at room temperature,preparing samples at different reaction time periods.CoFe-PBA@ZIF-67-2 h,12 h and 24 h,the composite material retains the regular dodecahedron frame of ZIF-67 at different times.CoFe-PBA@ZIF-67-12 h sample performance is the best due to the degree of CoFe-PBA and ZIF-67 complex exactly provide enough active sites,more conducive to ion migration.CoFe-PBA@ZIF-67-2 h has well performance attribute to its core-shell structure.CoFe-PBA@ZIF-67-24 h has the worst performance and the longer recombination time leads to more CoFe-PBA covered on the surface of ZIF-67,making it difficult for ZIF-67 to participate in ion migration.