Table 3.

Comparison of the properties of N-doped carbon materials prepared by different methods.

Raw Materials and Preparation Methods	Advantage	Electrochemical Properties
Carbonization of freeze-drying chitosan-boric acid aerogel beads [44]	High performance; multiple atomic doping	The specific capacitance was 217 F/g at a current density of 1 A/g. The capacitance retention rate was 95.1% after 10,000 cycles of charge and discharge at a current density of 5 A/g. Energy density was 7.2 Wh/kg at a power density of 4.984 kW/kg.
Co-HTC of cellulose and ammonium sulfate [46]	High specific surface area; multiple atomic doping	The specific capacitance at 1 A/g current density was 227.3 F/g, the capacitance retention rate at 20 A/g current density was 76.55%.
Co-HTC of cellulose and pyridine [47]	High capacitance retention; two-stage HTC	The specific capacitance is 214.1 F/g at a current density of 1 A/g. After 10,000 charge–discharge cycles at a current density of 5 A/g, the capacitance retention rate is 97.82%.
Co-HTC of cellulose and thiourea (This study)	High specific capacitance; high cycle retention rate; simple process	The specific capacitance reached 235.8 F/g at a current density of 1 A/g. After 20,000 charge and discharge cycles at a high current density of 10 A/g, the capacitance retention rate was 99.96%. Energy density was 29.24 Wh/kg at a power density of 0.5 kW/kg.