Microwave Absorption And Electrocatalysis Performance Of Porous Carbon Encapsulated Metal Nanoparticles

As a functional material,the porous carbon materials have attracted extensive attentions due to good conductivity,high specific surface area and light weight.In recent years,a large number of researches on porous carbon materials in the field of electromagnetic wave absorption and electrocatalysis are emerging.In the microwave absorption aspect,a lot of electromagnetic waves are reflected on the surface of materials because of the overlarge relative dielectric constant of porous carbon materials,resulting in poor microwave absorption performance.In the field of electrocatalysis,the electrochemical activity of porous carbon materials is weak,so it is necessary to improve the electrocatalytic performance of porous carbon materials.The previous researches indicated that carbon materials as conductive network are combined with metal nano materials,which is valid to tune electromagnetic parameters and increase active sites of composites for notably enhancing microwave absorption and electrocatalytic performance.In the view of above problems,the porous carbon material employed as the framework were composited with the metal copper and nickel in this work.It is effective that adjusting the mass ratio of the composites to obtain good-performance microwave absorption materials and high-activity electrocatalysts.In this paper,the Cu/C and Ni/C porous composites with different carbon proportion were prepared by a unique and efficient annealing method.The morphologies and structures of porous Cu/C and Ni/C composites were analyzed by SEM and TEM.It was found that the metal nanoparticles display the agglomeration in the low carbon concentration composite.With the increase of carbon content,the nanoparticles are dispersed uniformly in the porous structure and the size of nanoparticles decreased.The size of nickel nanoparticles varied from 300 nm to 50 nm.The overall size of Cu nanoparticles did not change much and remained within a few tens of nanometers.The microwave absorption performance of two composites increases gradually with the enhancement of carbon concentration at first,and then decreases with the further increase of carbon concentration.The Cu/C 1-3 and Ni/C 1-3 composites display the optimal microwave absorption property.For the Cu/C 1-3 composite,the reflection loss(RL)value of-56 dB was obtained at 17 GHz with a thin thickness of 1.4 mm.The minimum reflection loss value of Ni/C 1-3 composite exhibits-56 dB with a thickness of 1.8 mm at 15.8 GHz.The Ni/C 1-3 composite exhibits superior microwave absorption ability than Cu/C 1-3because the magnetic component Ni provides magnetic loss for the attenuation of electromagnetic wave.In addition,the oxygen evolution reaction of Cu/C composites was measured,and Cu/C 1-2 composite displayed slightly superior oxygen evolution performance.The onset potential and tafel slope of Cu/C 1-2 composite are 1.6 V and 152.8 mV/dec,respectively.The Ni/C composites possess better oxygen evolution capacity than Cu/C composites due to the excellent electrochemical activity of the metal Ni.The Ni/C 1-2 composite has optimal oxygen evolution performance.The overpotential is 341 mV at 10 mA/cm~2,and the tafel slope is 46.1mV/dec.In the oxygen reduction reaction test of composite system,the catalytic ability of Cu/C 1-4 and Ni/C 1-2 composite is slightly superior than that of other samples.The half-wave potential of Cu/C 1-4 composite and Ni/C 1-2 composite is 0.55 V and 0.67V,respectively.The ultimate current density of Cu/C 1-4 composite and Ni/C 1-2composite is 3.5 mA/cm~2 and 2.4 mA/cm~2 at 1600 rpm,respectively.