Cyanoethyl cellulose-derived N-doped carbon nanosheets as electrode materials for electrochemical supercapacitors

Supercapacitors, as next-generation energy storage devices enabling rapid electrical energy storage/release, are widely used in portable electronics, backup power systems, and hybrid electric vehicles. Biomass-derived porous carbon electrodes have emerged as a prominent research focus in energy storage. Two-dimensional carbon nanosheets have gained significant attention due to exceptional properties, including high conductivity and large specific surface areas. In this paper, cyanoethyl cellulose (CEC) nanosheets with an average thickness of 10 nm and ordered surface morphology were prepared utilizing the antisolvent method. Subsequent carbonization yielded nitrogen self-doped carbon nanosheet electrode materials (denoted as CNPC-X, where X represents the carbonization temperature). These materials exhibit a large specific surface area (1062.82 m² g⁻¹), abundant heteroatomic functional groups, and hierarchical pore architecture. This distinctive structure provides numerous ion transport channels to enhance diffusion kinetics while exposing readily accessible active sites, enabling a tunable balance between electric double-layer capacitance (EDLC) and pseudocapacitance. The CNPC-600 exhibits substantial pseudocapacitance, delivering a specific capacitance of 454 F g⁻¹ at 1 A g⁻¹, significantly exceeding CNPC-700 (252.2 F g⁻¹). In contrast, the CNPC-700 demonstrates dominant EDLC behavior, achieving a remarkable cycling stability of 96% after 2000 cycles and an exceptional capacitance retention of 82.2% at 10 A g⁻¹. Furthermore, the assembled symmetric supercapacitor device (CNPC-600//CNPC-600) achieves an energy density of 14.04 Wh kg⁻¹ and power density of 3.94 kW kg⁻¹, highlighting its potential for practical energy storage applications.