Construction And Capacitive Properties Of Cobalt-based/biochar Composites

In order to solve problems such as environmental pollution and energy crisis,energy conversion and storage devices have attracted great attention,especially energy storage devices.How to store limited energy is a problem that needs to be solved urgently.Supercapacitor is a new type of energy storage device,which has the advantages of high power density,fast charging and discharging process,good reversibility and so on.Cobalt-based compounds have the characteristics of good chemical stability and excellent electrical conductivity.However,when used as supercapacitor electrode materials,they still have problems such as small specific surface area and fewer active sites.This limits its practical application,so this article combines cobalt-based and biomass charcoal to play the coordinating role of cobalt-based and biomass charcoal,improve its overall supercapacitor performance.On the other hand,because biomass charcoal is renewable,it can be used as a support material to meet the requirements of circular economy and environmental protection,and it can also solve the problem of utilization of lunar calendar waste.The research content mainly includes the following aspects:（1）CoO/C was successfully synthesized by hydrothermal method with rice straw as the support and used as the active substance of supercapacitor material.The influence of the composite on the morphology and ultracapacitors was investigated.The composite was characterized by XRD and SEM and its electrochemical performance was tested.The research results show that CoO is evenly distributed in the composite and binds well to C.When used as a supercapacitor electrode material,CoO/C exhibits excellent electrochemical performance,with a specific capacitance of about 390.63 F/g in a 6 mol/L KOH solution.And the capacitance of CoO/C remains at 91.2% of the initial capacitance,indicating that CoO/C has a higher cycle life.（2）The NiCo₂O₄/C electrode,NiCo₂O₄/CB electrode and NiCo₂O₄/CNF electrode were prepared by hydrothermal method with the carbonized straw,bamboo flake and carbon nanofiber as the support materials respectively.Electrochemical test results show that among different biomass charcoal supports,the material with straw as the support has the largest specific capacitance,which is 629.88 F/g at a scan rate of 5 m V/s,and the highest capacitance retention.The post-discharge specific capacitance retention rate was 95.8% with 2000 cycles,indicating that the prepared electrode material has excellent cycle stability.Comparing the biochar composite material with the traditional carbon material CNF,the biomass charcoal has better supercapacitor performance,is green and environmentally friendly,and does not pollute the environment.（3）NiCo₂O₄/C and CoFe₂O₄/C composites were prepared by hydrothermal method using carbonized rice straw as support.In the electrochemical test,the specific capacitance of NiCo₂O₄/C electrode material was 629.88 F/g at a scan rate of5 m V/s.The specific capacitance of the electrode material of CoFe₂O₄/C is 458 F/g at a scan rate of 5 m V/s.The specific capacitance of CoFe₂O₄/C and NiCo₂O₄/C can maintain 93% and 95.8% of the initial capacitance after cycling.Studies have shown that NiCo₂O₄/C has a larger specific capacitance and better cycle stability.（4）CoZn/C was successfully synthesized by hydrothermal method with bamboo tablets as the support,and the effect of cobalt-based derivatives on morphology and ultracapacitor performance was investigated.The derivatives were characterized by XRD,SEM,TEM and XPS,and their electrochemical properties were tested.The research results show that the CoZn/C electrode has better supercapacitance performance,higher specific capacitance,longer constant current charge and discharge and better cycle stability.The specific capacitance of the CoZn/C composite material at 5 m V/s is calculated to be 757.8 F/g.After 2000 cycles,the specific capacitance retention rate of the CoZn/C electrode is 96.7%,respectively.The CoZn/C electrode material has better electrical properties.