Nitrogen-rich hierarchical porous carbon materials with interconnected channels for high stability supercapacitors

Novel nitrogen-rich hierarchical porous carbon (NPC) materials have been successfully synthesized using eggshells as the template and activation agent. Because the eggshell template with a unique porous structure is made mainly of calcium carbonate, it can decompose into carbon dioxide (CO) and calcium oxide (CaO) during the carbonization process, and a hierarchical porous carbon material is generated when the produced CO gas is released and the formed CaO is removed. Moreover, a certain amount of polyvinyl pyrrolidone (PVP) is added to introduce nitrogen element and form a special morphology with lots of interconnected channels in the carbon wall. The hierarchical porous structure with abundant functional groups and interconnected channels not only facilitates electrolyte ion transportation, but also improves the electrochemical stability of the carbon materials. As a result, the as-prepared samples show excellent electrochemical performance. Particularly for the NPC4 sample, it maintains a high capacitance retention of 85% when the current density increases from 0.5 to 10 A g, and the specific capacitance is still retained at approximately 98% even after 10 000 cycles. Thus, the as-prepared NPC is a great potential electrode material for high stability supercapacitor application.