Facile synthesis of nitrogen-enriched nanoporous carbon materials for high performance supercapacitors

Mesoporous carbons with ultrahigh nitrogen content were prepared for supercapacitors through the hard template method. Silica nanoparticles were used as the hard template, and ethylenediamine and CCl₄ served as precursor. Large amount of mesopores were generated through removing the silica nanoparticles with HF. The effect of carbonization temperature on the pore structure and nitrogen content and thus on the capacitive performance of supercapacitors were investigated. It was found that the higher carbonization temperature leads to an initial increase and then decrease of specific surface area and a continuous decrease in N content. The sample carbonized at 700 °C (NC700) shows the highest capacitance (306 F g^-1) due to the higher surface area (533 m² g^-1) and ultrahigh N content (18.06%). The increase in specific surface area results in improvement of double-layer capacitance, while the N element increases the pseudocapacitance and the wettability of the carbons. In addition, NC700 shows excellent stability with 96.6% capacitance retention even after 10,000 cycles at a current density of 3 A g^-1.