Lignin-based Carbon/iron Oxides Composite Nanofibers As An Application Electrode Materials For Supercapacitors

Lignin,the second most abundant polymer in nature,is also considered to be the only and largest biomass source of aromatic functionality,making it the most attractive sustainable precursor for carbonaceous materials.In this study,carbon/Fe composite nanofibers(CNFs)were fabricated by electrospinning or co-axial electrospinning bamboo acetic acid lignin(AAL),polyethylene oxide(PEO)and iron(III)acetylacetonate(AAI)compound solutions,followed by stabilization and carbonization processes,while polyvinylpyrrolidone(PVP)as pore inducer and poly(styrene-co-acrylonitrile)(SAN)as core electrospinning solution.The thermodynamic properties of nano fibrils were carried out by thermal gravity analysis(TGA).The morphology of composite carbon nanofibers were studied with a field emission scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The crystal and molecular structures of as-prepared composite carbon nanofibers were investigated by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and Raman spectroscopy.The specific surface areas and pore-size distributions of the samples were evaluated by an automatic adsorption system.The as-prepared carbon/Fe composite nanofibers were used as electrode materials of supercapacitors.Cyclic voltammetry(CV),galvanostatic charge/discharge(GCD)and electrochemical impedance spectroscopy(EIS)analysis were carried out to evaluate electrochemical performance of the electrodes.The results were as below:1.Lignin-based porous carbon nanofibers(PCNFs)were fabricated by electrospinning while PVP as pore inducer in electrospinning solution.The fiber diameters were all around 200~400nm;iron oxide particles with diameters of 20~50nm were exposed outside and well-distributed in PCNFs.The iron oxide particles were a mixture of hematite,magnetite and iron metal.The PCNFs were used as electrode materials.The electrochemical tests of the electrode were carried out in a typical three-electrode setup.It is found that the electrode undergoes redox reaction and exhibite peusocapacitor behavior,and the largest specific capacitance of the electrodes was 67.05 F/g as mass ratio of AAI was 15%.2.Lignin-based hollow composite carbon nanofibers(HCNFs)were fabricatied by co-axial electrospinning while SAN as core electrospinning solution.The fiber diameters were all around 300~500nm;The iron oxide particles were a mixture of hematite,magnetite,iron metal and iron carbide.The HCNFs were used as electrode materials.t is found that the electrode undergoes redox reaction and exhibite peusocapacitor behavior,and the largest specific capacitance of the electrodes was 121.49 F/g as mass ratio of AAI was 25%.3.Lignin-based porous hollow carbon nanofibers(PHCNFs)were manufacted by co-axial electrospinning while SAN as core electrospinning solution and PVP as pore inducer in shell electrospinning solution.The fiber diameters were all around 300~500nm;The iron oxide particles were a mixture of hematite,magnetite and iron metal.The PHCNFs were used as electrode materials.It is found that the electrode undergoes redox reaction and exhibite peusocapacitor behavior,and the largest specific capacitance of the electrodes was 102.04 F/g as mass ratio of AAI was 15%.