Preparation of Dual-Doped N/P Two-Dimensional Porous Carbon Nanosheets for High-Performance Alkaline Supercapacitors

Combining multiple heteroatom codoping with unique 2D carbon nanoarchitecture is an appealing strategy for enhancing the electrochemical performance of carbon electrodes. In this work, we offer a two-step avenue to manufacture N/P codoped 2D porous carbon nanosheets (NP-PCNs) for supercapacitor electrodes. The 2D PCNs are first obtained via the explosion-assisted technique along with carbonization and acid washing using zinc nitrate and lactose as raw materials. Then, the PCNs are coated by poly(cyclotriphosphazene-co-polyethyleneimine) as carbon, phosphorus, and nitrogen sources, followed by direct carbonization to produce NP-PCNs. The resultant optimized sample NP-PCNs-100 integrates the architectural features of rich heteroatom codoping amount (3.47 at. % for N and 2.64 at. % for P), moderate specific surface area (239 m2 g-1), and hierarchical porosity (micro-, meso-, and macropores). Electrochemical tests display that the NP-PCNs-100 presents a high specific capacitance of 322.9 F g-1 at 1 A g-1 and maintains its specific capacitance of as high as 64.4% (207.9 F g-1) at 20 A g-1, manifesting an attractive rate performance. Moreover, the assembled symmetrical supercapacitor device using the typical sample NP-PCNs-100 can achieve a high energy density of 17.04 W h kg-1 at a power density of 400 W kg-1 and deliver a superb cycling stability (capacitance retention of 90% after 10,000 cycles).