Research On The Application Of Two-dimensional Layered Materials In The Field Of Supercapacitors And Electrorheological Changes

Two-dimensional nanomaterials have been attracted great concern due to their excellent electronic,optical and mechanical properties,especially layered double hydroxides?LDH?and two-dimensional transition metal carbides and nitrides?MXenes?,which shows potential application value in the fields of energy storage,electrorheology,composite material enhancement,biosensors,lubrication,light,electrochemical catalysis,etc.However,there are shortcomings that MXenes are easily oxidized and stacked between layers of LDH.In this work,we used a simple method?hydrothermal method,surface oxidation,etc.?to prepare new type of high-performance two-dimensional layered composite material,and successfully applied it in the field of supercapacitors and electrorheology,and explore its application potential in the field of supercapacitors and electrorheology.In this work,the CoS₂ nanosheets are densely grown on the surface of Ni foam through the hydrothermal reaction.Subsequently,the as-synthesized CoS₂@Ni was then coated with flower-like NiFe-LDH nanospheres with lamellar structure through another hydrothermal procedure to obtain the NiFe-LDH@CoS₂@Ni.Additionally,the as-prepared hierarchical NiFe-LDH@CoS₂@Ni hybrids were directly utilized to fabricate a binder-free electrode which presented an outstanding capacitive performance owing to the unique flower-like structure.The final results showed that NiFe-LDH nanospheres prepared with 10 hours hydrothermal conditions exhibits excellent capacitance performance.The prepared NiFe-LDH@CoS₂@Ni electrode presents an outstanding capacitance of 11.28 F cm^-2(3880 F g^-1)at 2 mA cm^-2(1.17 A g^-1)in the three electrodes system.What's more,an all-solid-state asymmetric supercapacitor?ASC?was assembled by applying the as-prepared NiFe-LDH@CoS₂@Ni hybrid as the positive electrodes and active carbon covered Ni foam as negative electrodes,respectively.The as-fabricated ASC presented a high energy density of 15.84 W h kg^-1 at the power density of 375.16 W kg^-1 and can be able to lighten a blue LED indicator for more than 30 min,revealing that the prepared NiFe-LDH@CoS₂@Ni presents great potential for practical applications.Therefore,the prepared NiFe-LDH@CoS₂@Ni with outstanding electrochemical properties should envision potential practical applications in high-performance supercapacitors.In the two-dimensional nanomaterials family,the new MXene nanosheets have a high dielectric constant and a large specific surface area,but are easily oxidized.The Nb₂CT_x MXene was prepared by HF etching,and then oxidized via hydrothermal method and CO₂ calcination derivatizing into a layered Nb₂O₅/C composite.It was successfully used as an ER material.The composite prepared by hydrothermal method showed an excellent ER effect.As for the composite prepared by CO₂ calcination,thinner carbon layer substrate and more Nb₂O₅ nanoparticles were displayed with reducing heating rate increasing calcination temperature,leading to an interesting electroresponsive behavior with great research value.This work broadens the application of MXenes and provides a possible pathway to predict and optimize the ER application for other 2D materials.