Preparation And Application Of Chitosan-based Carbon Aerogels Anchored By Transition Metal Oxides

The transition metal Oxide has a relatively many empty d or f orbitals that can be bonded and can bind to the reactant molecules to form a transition state with a lower energy barrier,thereby reducing the activation energy of the whole reaction path so that it can accelerate the chemical reaction.In general,the same MO_x has a variety of physical and chemical properties,can be used as electrode materials,catalytic materials,microwave absorbing materials and other widely used in various fields.However,most of MO_x belong to semiconductors and has poor conductivity,so they usually need to be modified by carbon materials with excellent conductivity.For example,carbon nanotubes,carbon nanofibers,carbon nanosheets,graphene,carbon aerogels and so on.In this paper,a rapid combustion method was designed to prepare MO_x/nitrogen-doped carbon aerogel(NCA)nanocomposites,such as NiO_x/NCA and CoO_x/NCA,FeO_x/NCA,MnO_x/NCA,ZnO_x/NCA.Biomass chitosan aerogel used to raw material.The rapid combustion method is a method in which a transition metal oxide is uniformly doped in a carbon layer by heating a transition metal nitrate and an aerogel.At the same time,MO_x/NCA nanocomposites were characterized by physicochemical characterization,which showed broad application prospects in lithium-ion battery anode materials,catalytic synthesis of vinyl acetate catalyst,microwave absorbing materials and so on.The relevant research contents are as follows:(1)MO_x/NCA nanocomposites were prepared by rapid combustion method.MO_x/NCA nanocomposites were successfully prepared by rapid combustion using biomass chitosan aerogel as raw material.It was found that the density of the product decreased with the increase of aerogel content.Among them,NiO_x/NCA can be used in the field of magnetic absorption.When the absorption layer is 3.5 mm,the maximum absorption value of NiO_x/NCA is 6.5 GHz,and the maximum absorption value is-28.41 dB.FeO_x/NCA and MnO_x/NCA show excellent electrocatalytic activity for Oxygen evolution and can be used in the field of electrolytic water.When the Oxygen evolution(OER)reaction is tested,when the current density is less than 10 mA/cm~2,the overpotential required by FeO_x/NCA is 297 mV,Tafel slope is 68mV/dec.To test the(HER)performance of hydrogen precipitation reaction,When the current density is less than 10 mA/cm~2,the overpotential required for MnO_x/NCA is 181 mV and the Tafel slope is 149.43mV/dec.ZnO_x/NCA has excellent catalytic performance for the synthesis of vinyl acetate,and the conversion of acetic acid is 69.1%when the reaction time is 11 h.At the same time,MO_x/NCA as lithium anode material also shows its application potential.This study provides a new method for the rapid preparation of MO_x/NCA nanocomposites.(2)Preparation and properties of Ni-NiO/NCA electromagnetic absorbing materials.Ni-NiO/NCA was successfully prepared from biomass chitosan aerogel by rapid combustion method.The results revealed that the densities of NCA and Ni-NiO/NCA are 0.46 g/cm~3 and 0.42 g/cm~3,respectively,which shows excellent dielectric properties.In particular,Ni-NiO/NCA exhibits excellent magnetic and microwave absorbing properties.When the absorption layer is 1.5 mm and the frequency is 15.2 GHz,the maximum absorption value is-41.9 dB.This study provides a new idea for the preparation of lightweight magnetic microwave absorbing materials.