Nitrogen-doped mesoporous graphene with fine-tuned pore size in a few nanometer-scale for supercapacitor applications

Nitrogen-doped mesoporous graphene (NMG) was successfully synthesized by a soft-template method, using graphite oxide (GO) and triblock copolymer (Pluronic P123) in the presence of ammonia water. To finely tune the porous nature through controlling the micellization behaviour of P123, the mesostructured graphenes were washed under different washing conditions. As a result, the synthesized NMGs exhibit 3D porous structure with high surface area (941–1297 m² g⁻¹) as well as fine-tuned pore size (4.4–11.2 nm) at a few-nanometer scale. Also, to find the optimal temperature for the best supercapacitor performance, the annealing temperature was regulated at 500 °C, 700 °C, and 900 °C. The content and configuration of nitrogen in NMG were rationally controlled as a function of annealing temperature, which strongly influences the electrical conductivity and supercapacitor performance. The highest capacitance of 284 F g⁻¹ was achieved for NMG calcined at 700 °C with a current density of 0.1 A g⁻¹. Furthermore, it shows good cycle stability with ~98% retention of its initial capacitance at a current density of 3.0 A g⁻¹, even after 5000 cycles.