Nitrogen-Doped Porous Carbon with Staged Nanopore Formation for Capacitors

The design of nanopore structures in porous carbon materials plays a crucial role in achieving high capacitance and rate performance in capacitors. This study introduced a method for the synthesis of high specific surface area nitrogen-doped porous carbon (HNPC) materials by staged nanopore formation. The method involved designing a composite reaction precursor using oxalic acid (H2C2O4), p-phenylenediamine (PDA), and potassium hydroxide (KOH), as well as creating micropores during the pyrolysis process and constructing micropores and mesopores during potassium carbonate (K2CO3) activation stage. HNPC materials synthesized in this study demonstrated a high specific capacitance and exceptional rate performance in aqueous electrolytes across a broad pH spectrum (acidic, neutral, and alkaline) as well as in organic electrolytes. Specific capacitances of 263.3 F g–1, 366.1 F g–1, and 304.4 F g–1 (at a scanning rate of 2 mV s–1) were attained in 1 M lithium sulfate (Li2SO4), 6 M KOH, and 1 M sulfuric acid (H2SO4) electrolytes, respectively, indicating high capacitance values. By configuring them as symmetric supercapacitors, they performed high energy densities of 8.2 Wh kg–1 and 22.9 Wh kg–1 in aqueous and organic electrolytes, respectively, while maintaining capacity retention rates of 81.2% and 83.9% after 10 000 and 5000 cycles.