Surface functionalization of PS/PEI-derived hierarchical porous carbons doped with nitrogen and oxygen using melamine activation for supercapacitors

The specific performance of supercapacitors can be enhanced by the incorporation of carbon materials with high surface area and nitrogen- or oxygen-functionalities. In this study, we have designed nitrogen-doped hierarchical porous carbon materials with oxygen-containing functional groups. The PS-Cl resin not only acts as a carbon precursor, but also contains the O element to provide oxygen-containing functional groups, which leads to an improvement in surface wettability and pseudo-capacitance. The graft of PEI provides the N source and protects the O atom, thus obtaining more active sites. In addition, the introduction of melamine is a key factor to generate a hierarchical porous structure, and it can also serve as a source of nitrogen, thereby increasing electrical conductivity. The resulting products have a moderate surface area (469-1000 m2/g), a rich oxygen functionality (6.10-13.16 atom %), and an N content (6.83-16.3 atom %). In the three-electrode system, the electrode material of N-PHPC-700-2 exhibits an outstanding specific capacitance of 339 F g-1 and maintains the stability at 98.65 % after 10,000 cycles. The symmetrical supercapacitor based on the N-PHPC-700-2 electrode material shows a high energy density of 19.67 Wh kg-1 at a power density of 425.04 W kg-1. This study provides a method for the preparation of porous carbon with a high concentration of nitrogen and oxygen atoms.