Preparation Of Electrode And Research Of Supercapacitor Properties Based On Nickel/Cobalt Oxides Composite

What can be the key measure for dealing with crucial environmental problems:the greenhouse effect and the over-exploitation or use of fossil resource,is to explore,design and construct new energy-storage materials with high performance,low pollution and cost,as well as to seek novel green and renewable energy.Supercapacitors,which possesses high power density,superior cycle life,low toxicity,eco-environment and high work-efficiency,have been capturing much attention from both academic researchers and industry.Nickel/Cobalt based metal oxides are the most suitable active materials for electrochemical electrodes and catalysts,due to their high electrochemical activity and also abundant reserves,as well as low cost.Nevertheless,electrochemical electrodes based on pure nickel or cobalt oxide,on one hand,the single morphology and the phase structure cannot meet the requirement of designs;on the other hand,due to the intrinsic lower conductivity of semiconductor oxides,the carrier concentration as well as the number of active sites and defects of the materials are seriously limited,which restrict the real activity of nickel and cobalt.Therefore,when nickel/cobalt was used as the active matrix to construct the composite,the unique character and intrinsic advantage of each element can be combined to achieve complementary,so as to improve or even completely overcome the above shortcomings.Meanwhile,electrodes based on multi-component materials are able to achieve much higher performance in electrochemical reactions,owing to enhancement the synergistic effect.In this paper,from the angle of constructing composite material based on nickel/cobalt as active material,the performance of electrochemical devices is improved by design synergistic effect between components and enhance the conductivity of nickel/cobalt oxides in the meantime.The main work is focused on the following aspects:1.Employing CTAB as soft template reagent,the ordered mesoporous structure is constructed to improve the specific area of materials and the loading area of the active component,which also benefit for the larger heterojunction layer and the contact with electrolyte.Surface modification process by silane reagent is used to enhance the adsorption to metal cations during the hydrothermal reaction.The porous structure enlarges the p-n heterojunctions based on the two-phase interface of the host-guest material,and enhances the electrochemical performance of OM-Ni O/Zn O,due to the electronic synergistic effect in the near region of p-n junction layer.The specific capacitance is as high as 2323 F g^-1,and exhibits great rate capability and cycling stability.Meanwhile,the paper proposes an electronic synergistic mechanism based on p-n heterojunctions.This work provides a novel way for the structural design of composites as well as the application of porous materials and p-n heterojunction structure for new type of energy storage materials.2.In order to adjust the distribution of Co on the surfaces of graphene,chloroacetic acid is employed to taken the Carboxylation treatment to reconstruct the functional group on the surface of GO.Na BH₄ is used as reducing agent for the growth of Co clusters during the hydrothermal reaction.For the electrochemical reaction in liquid usually acts on the interface of the electrode material and electrolyte,with the increase of the load of the active material,the thickness of active material shell will also get large,which makes the conductivity of the electrode decrease sharply and weaken the synergistic effect between the core and the shell.Based on this premise,by controlling the calcination temperature,only the metal surface layer is oxidized,and the bidirectional coating structure r GO@Co@Co₃O₄ composite is finally constructed.The intermediate Co layer can enhance the conductivity of composite as the bridge transition layer,and meanwhile,the unique free-electron cloud model of metals is able to form an electronic synergistic effect between Co and the external Co₃O₄ layer,beneficial to the utilization of active materials and electrochemical performance.The graphene layer,as the core layer,can further strengthen the stability of Co@Co₃O₄ in a long continuous electrochemical reaction process.