Preparation of iron-modified cellulose carbon aerogel and its research for supercapacitor electrodes

2,2,6,6-tetramethylpiperidine-1-oxygen radical (TEMPO)-oxidized cellulose (TOCNF) as one of the ideal precursors for biomass-based carbon materials has the advantages of large specific surface area and renewability. However, its application in the field of supercapacitor electrodes is limited due to problems like poor conductivity and low specific capacitance after carbonization. Doping with iron ions is one of the effective means to improve its electrochemical performance. In this study, Fe³⁺ was introduced into TOCNF by the impregnation method, and then Fe³⁺-doped carbon aerogels were prepared through the sol-gel method, freeze-drying, and carbonization. These aerogels were used as supercapacitor electrode materials. The effects of Fe³⁺ doping on the elemental composition, structure, and microstructure of the carbon aerogels were investigated by methods such as SEM, XRD, XPS, specific surface area and pore size analysis, and Raman spectroscopy. Their electrochemical performance was tested using an electrochemical workstation in both three-electrode and two-electrode systems. The results show that the Fe³⁺-containing carbon aerogel material Fe50/CTOCN, doped with 0.05 mol∙L⁻¹ FeCl₃ solution, has a high specific surface area of 1482.89 m²∙g⁻¹, and the degree of graphitization is significantly improved. Moreover, it has a specific capacitance of 248 F∙g⁻¹ at a current density of 0.5 A∙g⁻¹, showing the best electrochemical performance. The symmetric supercapacitor composed of Fe50/CTOCN has an energy density of 3.45 Wh∙kg⁻¹ at a power density of 200 W∙kg⁻¹, and the specific capacitance remains 90% after 5000 cycles, exhibiting excellent cycle stability.