Facile preparation of N-doped porous carbon nanosheets derived from potassium citrate/melamine for high-performance supercapacitors

Nitrogen (N)-doped porous carbon nanosheets have attracted research attention owing to their effective structure for fast ion diffusion and pseudocapacitive properties in supercapacitors. However, to synthesize N-doped porous carbon nanosheets while maintaining their original shape requires complicated multistep processes such as plasma and arc-discharge methods. Herein, we propose a facile and effective method for N-doping into interconnected porous carbon nanosheets that preserves their original structure with a stepwise thermal annealing using melamine as N-doping source. The stepwise thermal annealing is advantageous to improve N-doping efficiency into the carbon matrix compared to direct thermal annealing method owing to the condensation of melamine. As-synthesized N-doped carbon nanosheets with interconnected and porous structure exhibits high specific surface area and N-doping contents, which favorable for the fast ion movement, adsorption, and increasing the wettability of the electrolyte. The electrochemical performance shows a maximum specific capacitance of 350F g-1 at 1 A g-1 in a three-electrode test. Moreover, a fabricated symmetric full-cell device using an optimized N-doped carbon electrode demonstrates a long-term durability over 10,000 cycles and a maximum energy density of 16.1 Wh kg-1.

Automated summary

Nitrogen-doped porous carbon nanosheets show promising electrochemical performance in supercapacitors due to their interconnected porous structure. A facile method involving stepwise thermal annealing with melamine as the N-doping source was proposed to maintain the original structure of N-doped carbon nanosheets. The as-synthesized nanosheets exhibited high specific surface area and N-doping contents, leading to improved ion movement, adsorption, and electrolyte wettability, resulting in a maximum specific capacitance of 350F g-1 at 1 A g-1 and excellent long-term durability in a symmetric full-cell device.