Electrochemical Property And Interlayer Regulation Of Graphene Based Two Dimensional Nanomaterials

With the advantages of large specific surface area and high atomic exposure ratio,nanosheet is leading the new trend of research and application of the super-crystalline composite material.In our previous works,the relationship between the interlayer spacing of two-dimensional functional material and their electrochemical property was studied.The evolution of nanosheet structures and the mass transfer process and energy storage mechanism in the electrochemical reaction of composite materials were analyzed.Based on the characteristics of two-dimensional nanomaterials,three methods of enlarging the interlayer spacing were summarized in this paper:self-supporting,self-assembly and design of hierarchical structure).P-phenylenediamine?PPD?was used to prepare the functionalized graphene?PRGO?networks.PPD in-situ oxidized to oligomers in graphene interlayer by replacing oxygen-containing functional groups on the surface of graphene oxide,which could effectively prevent Reduced graphene oxide aggregation under the action of?-?.When the mass ratio of PPD to graphene oxide is 1:1,the interlayer spacing was 0.9441 nm,the electrodes exhibit a specific capacitance of 320.50 F/g,88.69%of capacitance retains after recycled 1000 times.The result of PEIS showed that the process of electrode is controlled by both charge transfer process and diffusion process,composite material has a higher charge transfer rate,the solution impedance and the electrochemical impedance are 0.38??1.40?,respectively.V₂O₅ hydrosol was prepared by melt quenching method firstly,and then V₂O₅/RGO composites with good stability were prepared by supporting V₂O₅ mentioned above on tubular RGO when H₂O₂ was added to the reaction system.The interlayer spacing of V₂O₅and graphene was 1.2990 nm and 0.9019 nm,respectively.The larger interlayer spacing is beneficial to ion migration between nanosheets.The electrochemical structure showed that the V₂O₅/RGO composite was a double layer capacitor.When the mass ratio of V₂O₅ to GOs was 2:1,the electrodes exhibit a specific capacitance of 552.04 F/g in 0.5 mol/L Li₂SO₄ electrolyte,87.02%of capacitance retains after recycled 500 times.The result of PEIS showed that the electrode process was controlled by both charge transfer and diffusion processes,the solution impedance and the electrochemical impedance were7.54??4.91?,respectively.Hierarchical Nickel-Manganese layered double hydroxides nanospheres?Ni-Mn LDHs?with three-dimensional flower structure have been hydrothermally synthesized in a homogeneous precipitation of mixed Ni²⁺/Mn²⁺salts via the hydrolysis of hexa-methylenetetramine?HMT?and in situ oxidation with H₂O₂,the petal of which was a typical Stern double-layer capacitor.The structural evolution?electro-chemical properties and energy storage mechanism have been studied.We change the charge density of the main layer by using different mole ratio of Ni²⁺/Mn²⁺and using different intercalation anion to change the thickness of diffusion layer.The interlayer spacing of Ni-Mn LDHs was 0.9441 nm,exhibiting a specific capacitance of 1508.75 F/g,and 87.60%of capacitance retains after recycled 1000 times when n_Ni:n_Mn=2:1.The electrochemical reaction of the electrode is controlled by the semi-infinite diffusion of protons,and the diffusion constant was 13.80×10^-11cm²/s.The interlayer spacing of Ni-Mn LDHs increased to 0.8857 nm after intercalated byNO₃^-,exhibiting a specific capacitance of 1520 F/g,91.46%of capacitance retains after recycled 1000 times,both specific capacitance and stability of Ni-Mn LDHs improved after intercalation of NO₃^-.The electrochemical reaction of the electrode is also controlled by the semi-infinite diffusion of protons with a diffusion constant of 13.80×10^-1111 cm²/s.Ni-Mn LDH/PRGO supercrystal composites were prepared by one-step hydrothermal method using PRGO as a carrier.Due to the restriction effect of PRGO,the face-to-face heteroassembly of Ni-Mn LDH nanosheets on the surface of PRGO,while at the edge of graphene those nanosheets self-assembles into microsphere with three-dimensional flower structure,randomly.When the PRGO content was 10%,the electrodes exhibit a specific capacitance of 1715.0 F/g,98.93%of capacitance retains after recycled 1000 times,the electrochemical stability is improved significantly.